Preservation Matting for - Library of Congressmost of the preservation functions that the bound...

4 PFM February Supplement 1997

When we look at a Renaissance drawing on paper we arewitnessing a miracle of preservation. The drawing hashad to survive five hundred years during which it mightquickly have been destroyed by poor handling, bad cli-mate, or biological degradation. How can something asfragile as paper survive for such a long time?

Part of the answer is in the quality of the paper itself.Antique papers were made of stable fibers such as linenand did not contain enough lignin or harmful additivesto be self-destructive. Even the most robust paper couldbe destroyed by pollution or mishandling without a pro-tective storage structure.

This structure was the book. Books housed sheets ofvellum before paper arrived in Europe. These early bookshad to provide considerable restraint to keep their animalhide pages from cockling. They did this with strongwooden covers and leather and metal clasps which keptthem shut. Even when they were decorated with water-color, the steady, overall pressure of the closure of thebook did not disturb the pigment. Later, when papercame, the clasps were left off and the sewing structurechanged but books remained an ideal structure for pre-serving prints and drawings.

Drawings not originally executed as illustrations orilluminations in books were usually plans for buildings orstudies for paintings. Giorgio Vasari, the Italian architectand biographer of artists, was instrumental in creating anappreciation for drawings. He mounted drawings on larg-er sheets of paper and decorated the area around themwith designs that often approximate tabernacle frames.He then bound these sheets into books.

This practice spread and volumes of prints and draw-ings could be found in the libraries of many aristocratichouseholds. Some of these volumes had the edges of theirpages gilded which helped to keep pollution andextremes of humidity away. The mass of material whichwas stored together in the library also helped to maintainsteadier conditions. Ultimately, these volumes were bro-ken up and the drawings stored individually. During thisprocess, the question of how prints and drawings might

safely be stored and handled was successfully answeredwith the invention of the window mat at the BritishMuseum in the mid-nineteenth century.

When the drawing came out of the volume, it mightbe left on the sheet to which it had been mounted. Evenif the window mat exposed the entire drawing, it wouldcover, support and restrain the mount. Prints or drawingscould be stored horizontally in boxes or cabinets sincewindow mats of the same size would tend to have similaropenings. The alignment of their openings would alsocreate a zone of decreased pressure.

The practice of attaching a drawing to a larger sheetof paper that is similar to the paper on which the work isdone continues in some European institutions and iscalled “adding a false margin.” The use of Japanese tissuehinges to secure prints and drawings is less intrusive andhas more recently gained favor. In either case, the con-struction of the window mat is the same and it fulfillsmost of the preservation functions that the bound vol-ume once provided.

The mat is a storage, handling, and display stru c-t u re. It should provide physical support, that is gentleand steady, as well as chemically inert. The supportg i ven to a work of art should be similar to the supportg i ven to a baby in someone’s arms. The baby is nots q u e ezed or unduly restrained but is given broad gentles u p p o rt. Su p p o rts for books on display are, in fact,called “cradles.”

This metaphor is worth remembering when makingdecisions about how tight hinges should be or how a sinkmat should fit. The attributes of gentleness and steadinesscan be viewed as usefully contradictory in that each limitsthe other; together they establish a compromise. Thus, amat which presses too hard on the margins of a workmay be too steady: it may flatten raised parts of theedges. A mat which supports a work of art too gentlymay loose its grip if the frame is jarred: the art may comeloose. The first thing to consider in designing successfulmats is the nature of the board that will be used. Most ofthe boards available today for use in matting are laminat-

Preservation Matting for By Hugh Phibbs

ed. Two, four, six, and eight ply boards will provide pro-gressively more strength (and more depth if they are usedfor making windows). Two ply board is frequently usedin institutions for making cover windows and inserts onwhich the art is hinged to facilitate movement from amat of one size to another. Two ply boards can be used increating complex windows, but cannot be used for a win-dow because it will not provide enough depth, and itcannot be used as a backmat since it will not provide ade-quate support.

The minimum requirement for a window mat pack-age is a four ply window mat and a four ply backmat.This combination will provide a space of 1⁄16" in front ofthe art in the window and will be rigid enough to give asteady platform for hinging or handling. Thicker boardssuch as six or eight plys can provide a deeper separationbetween the art and the glazing, but their added expensemakes them unlikely choices for backmats in a shop.

The commonest sheet size for matboard is 32 x 40inches. In the past, this size was 32 x 44 and when quar-tered, it produced four pieces which were 16 x 22, a stan-dard size in many museums today. The modern boardcan be cut into four 16 x 20 pieces, a useful standardsize. Other commonly used standard sizes can be groupedaccording to their shapes into a set which includes moreelongated rectangles, including 9 x 12, 11 x 14 , 14 x 18,16 x 22 , 22 x 28, 26 x 34, and 30 x 40, and a morecompact set of rectangles, including 16 x 20 , 24 x 30,and 26 x 32. While most commonly available boards donot exceed 40 x 60 inch sheets, some can be found insizes ranging up to 60 x 104 inches.

Matboard is made from wood pulp or cotton fibers.Both are primarily cellulose: long, repeating chains ofsugar molecules. Wood pulp also contains significant por-tions of branching hemi-cellulose and lignin, a group ofcompounds which give strength to wood. Lignin candegrade and produce acids or peroxides which aredestructive to paper. Wood pulp which has been refinedto remove these destructive components is called alphacellulose. It should be free of virtually all lignin as cotton

is naturally.A board which only contained cellulosic fibers would

be soft and quite absorbent, like a blotter paper. To makethe stronger, more durable boards needed for mat mak-ing, other components are added. Sizings can give theboard more resistance to soiling. Calcium carbonate maybe added to make the board chemically resistant to thedepredations of environmental pollution (which canlower the board’s pH and lead to acid hydrolysis of itsfibers). Other materials such as activated charcoal or alu-minum silicates with specific porosities known as zeolitesmay be included in boards to adsorb, or physically bondwith pollutants. Adhesives are also needed to bond theplys together: those most commonly used are polyvinylacetates and starches or modified starches.

The composition of the board should be a guide toits usage. Boards which are made of unpurified woodpulp, sometimes called paper matboards, should not beused for preservation. The addition of calcium carbonateto such boards should make them more durable, but maynot eliminate their potential for contamination of othermaterials.

Once the wood pulp has had the non-cellulosicp o rtions re m oved, it should be similar to cotton in itschemical stability and inertness. Cotton has the adva n-tage of being virtually lignin free naturally.C o n s e rvation quality boards made of purified woodpulp or alpha cellulose may be re f e r red to as conserva-tion boards, while those made of cotton are often calledmuseum or rag boards. The term rag should not beunderstood to imply that reclaimed textiles have beenused to obtain the cotton; it comes from the portion ofcotton left on the bole after the textile cotton has beenre m oved and is refined as linters.

Board which is made of cotton which does not havecalcium carbonate added is called photographic board.This may be used with materials which are alkaline sensi-tive. Highly reactive metals such as silver, copper, or lead,or protein based textiles such as silk or wool and photo-graphic media such as gelatin or albumen may be candi-

Works of Art on Paper


dates for housing with a pH neutral or photographicboard. Those photographic boards which are laminatedwith starch-based adhesives are safest, since polyvinylacetate adhesives which are mishandled in manufacturingcan degrade and off gas components of acetic acid, andthere will be no alkaline reserve in the board to counter-act it.

Opinions among photographic conservators vary asto the necessity of using this neutral board. Since theconcern involves contact between alkaline material andthe photograph’s (protein and therefore acid) emulsion,strips of unbuffered interleafing tissue placed between theemulsion and the mat should suffice when the photo isovermatted. The edge strips described in the PFMFebruary 1994 Preservation Supplement can be made ofsuch tissue and will isolate the emulsion. If the photo isfloated, there is no problem since the board will nottouch the emulsion.

It is important to remember that the chemical andphysical factors which may come into play in the life of awork of art in a frame are numerous and difficult toidentify exactly. We can only ask science for guidance,not for specific answers. In short, there is too much thatwe do not know. What are the roles of atmospheric pol-lutants, adhesives and other additives in the board, resid-ual traces of lignin, colorants, finishes, and interactions ofall of the above with light? Testing for one of these fac-tors may influence our choice of materials in one direc-tion, while others may be ignored.

Experience is invaluable here. Cotton-based boardshave been used for at least fifty years and alpha celluloseboards for almost half that long. Both have shown excel-lent results for storage and display of delicate material.Since chemically similar materials should have littlechance for reacting with one another, the use of thesepure paper-based boards next to a work of art on paperseems most reasonable.

Where a board has a colored or patinated paper onits surface, contact between that paper and the art shouldbe questioned. Has the manufacturer used the same strin-

gent requirements for the decorative surface paper as forthe core and backing paper? If this cannot be clearlyanswered affirmatively, then floating the art on that papershould be avoided unless an interleaf of conservationquality paper can separate them.

The paper which is in contact with the art maychange over time. It may, for example, take in gaseousemissions from the art or the environment. Very old ragmats which come off etchings may show stains whichcorrespond to the pattern of the print (the oils in theprinting ink may be expected to cause this sort ofchange). The board may be obviously darkened where itwas near the frame, but it may have also darkened overallin ways which cannot be seen readily because there is nofresh material with which to compare it. Because mat-board can be expected to take in pollution, it should bechanged on a periodic basis.

The means to keep pollution out of the mat packageare, fortunately, multiplying. The possibility of usingactive charcoal paper behind the mat package or mat-board with zeolites inside have already been mentioned.Both of these materials have seen long usage in buildingair purification systems. Those systems forced air throughthe scavenging material, and therefore, would be far morelikely to exhaust their storage potential than material in amat package would. Even if the art is left for far too longin a package which has been scavenging pollutants, andsome of those pollutants were eventually released, theycould not exceed the amount which would have gottento the art if no scavenger had been present.

Another material now entering the market not onlyphysically adsorbs pollutants, but chemically reacts withand inactivates them. This material is polyethylene sheetwhich has been impregnated with metallic copper. Asoxidizing gases pass through the plastic, the copper is oxi-dized by them and serves as a sacrificial scavenger. As thesheet reacts, it turns from copper colored to black, so itsexhaustion point is evident and easily monitored. A sheetcan be slipped between the backmat and the backingboard to combat the problem of atmospheric pollution.

Preservation Matting for Works of Art on Paper


Any of these materials can serve tokeep pollution from coming thro u g hthe back of the frame, but their poten-tial for scavenging pollutants whichmay be given off by works of art whicha re made of inferior materials is lessc l e a r. A molecule of a degraded pro d-uct, which might be generated by thepoor quality paper on which a workmay have been executed, will havemany chances to interact with thepaper before it reaches the surface andcan be scavenged after off gassing. It isi m p o rtant to remember that the mat isnot the only part of the frame whichcan serve to keep pollution away fro mthe art: the backing board can alsoaccomplish this. Boards which containplastic should slow the infusion ofatmospheric pollution into the matp a c k a g e .

Ultimately, the choice among themany good products on the market willdepend on the aesthetic and design pri-orities of the framer. If photographicboard is not readily available, pH neu-tral tissue can be used. The surfaceadjacent to the art can be either alphacellulose or cotton, and materials withscavenging capacities to hold out pollu-tion can be inside the mat or behind it.

Having chosen a board, one mustask how the mat package can be madefrom it. A window mat package com-prises the window and backmats whichhave been spined together with linentape along their longer side. This tapingpattern is very important to ensure thatthe window and backmats do notbecome misaligned when the mat pack-

Preservation M

age is not inside a frame. If the win-dow is not secured, it can come disas-trously loose during the unframingand it cannot serve as a secure hous-ing while the art is framed or storedin a drawer.

The mat package must be smallerthan the rabbet dimensions of theframe. This allowance is usuallyadded into the frame, so that a 16 x20 inch mat will go into a 161⁄8 x 201⁄8inch frame. Since few frames are her-metically sealed or are in unchangingenvironments, this allowance permitsthe board to both expand withoutpressing against the rabbet of theframe and to contract withoutshrinking past the inside of the lip.One eighth of an inch can serve as aneffective allowance for most frames.Jared Bark has reported that someboard can expand 1⁄8" over a length of40" with a ten percent rise in relativehumidity (PFM ConservationSupplement February 93). This sug-gests that when an oversized frame isbeing designed, the allowance shouldbe scaled up, as should the depth ofthe rabbet and lip of the frame.

Since the allowance has beengiven to the frame, the problem ofcutting the matboards to the rightsize should be straight forward. It iscomplicated somewhat by the ques-tion of whether the board comingfrom the supplier is square and ofexact dimensions. Usually the boardis neither. Manufacturers know thatif they make the board to the exactdimensions as specified, shrinkage

caused by drying might mean that itwould be too small in some areas. Toavoid such problems boards are usu-ally made slightly large.

If the cutting is to start fromone corner, the shorter edge shouldbe trimmed square at that corner. If aboard shears, also called a paper cut-ter, or a wall mounted combinationcutter is being used, it should beadjusted to ensure square cutting. If autility knife and straight edge are theonly tools available, a C-clamp at oneend of the straight edge and a prede-termined right angle on the workingsurface will greatly facilitate thisoperation.

Once the board has beensquared, the cuts can be laid out.Ideally, this could be done so that thegrain of the board would be parallelto the grain of the paper on whichthe art has been created. The difficul-ty of ascertaining the grain directionof the art paper, the size limitationsof the sheet of board, and theexpense involved make this impracti-cal. Proper hinge design, which willpermit some lateral movement of theartwork between hinges, is a bettermeans of addressing this issue.

Once the method for cutting hasbeen established, the issue of whatsize mat is to be cut can be consid-ered. Most shops will work out fromthe dimensions of the art to establishthe dimensions of the mat. Widths ofbetween two and three inches arecommon. At the smaller end of thisrange one might expect to find mats

Matting for Works of Art on Paper


for documents and maps or otheritems which tend to have blankspace which creates a borderaround their contents. Portraitsmay require mat borders whichexceed the three inch size to givethe subject “room.” Larger bordersmay also be employed for designpurposes.

In these layouts, it is commonto have the top and sides equalwith a larger bottom margin. Ifthis is done, the addition to thebottom should be large enough sothat no one will accidentally tapethe package together with the window upside down—anexpensive mistake.

Working with frames which have a standard size thatis independent of the mat opening presents more prob-lems. Here, the window and the frame will usually not becongruent rectangles, and extra space may have to beapportioned to both the top and the bottom margins ofthe mat. This can be done visually by laying the art ontop of the board and moving it into a position whichlooks accommodating. If the art is to be overmatted asimple tool can help here. An old mat which has been cutthrough at opposite corners can be used as a set of visualcalipers by overlapping the cut ends to create a propersize opening (see fig. 1). This tool can also help if a workwith an irregular design is to be overmatted, as theappropriate opening can easily be laid out and measured.

The measurement of the art requires a clean tapemeasure which will not pose any sort of danger to theart. Carpenter’s tapes may not readily lock in the openposition, and if they spring closed their hooked ends canput the edge of the art at risk. Also, it is difficult to accu-rately find the starting point on such tapes since theirend hooks are often loose. It is possible, in many cases tobegin the measurement at another point along the tapeto gain greater accuracy and safety as well as simplifica-

tion of the process. If the work being matted

is to be floated by 1⁄4" or is tohave 1⁄4" of paper visiblearound the perimeter of itsdesign, the measurement ofthe work can begin at the 1⁄2"point on the tape. This meansthat twice the required 1⁄4" willalready be factored into themeasurement and the appro-priate figure can be entered onthe worksheet. If the edge ofthe window will overlap thedesign, this technique will not

work. There are tapes available from sewing supply storeswhich are plastic impregnated cloth. These lack an endhook and lock in the open position, but may stretch ifplaced under tension and should not be trusted wherecomplete accuracy is needed.

The layout of the opening on the mat is quite simpleif the mat is sized to fit the frame. The sameness of theborders facilitates the use of production stops with a bar-type cutter, or the simple scribing of lines from the edgewhere stops are not used. The marking of windowsshould only be done with graphite or a tool which willcleanly incise the back of the window. If graphite is used,it must be thoroughly erased after the mat is cut usingonly a white vinyl eraser. Red or gray erasers can containsulfur which would contaminate the mat.

Laying out windows for mats which have standard-size borders can be more problematical. Here a tool fromthe hardware store, called a carpenter’s scribe, can beinvaluable. This tool comprises a ruled rod which is splitat one end to accommodate a marking point. A pencillead can be substituted for the point. The second compo-nent of this tool is a slide with a thumb screw that can heset at any point along the rod. This allows the pencilpoint to scribe a line along the rod at a given distancefrom one side as the tool is drawn along down that side.

Figure 1


The scribe also can function as a simple calculator.If a window that is 33⁄8" x 43⁄4" is to be marked in a

board which is 8" x 10", the measurements can be startedby considering the shorter side.Subtracting 3 inches from 8 inchesleaves 5 inches which must be appor-tioned between two of the sides ofthe mat, so the slide is first moved tothe 21⁄2 " point. The fraction 3⁄8" mustthen be divided into two portions of 3⁄16" and these mustbe added to each side of the opening. This can be doneby moving the slide 3⁄16" toward the pencil point so thatthe mat side is diminished and the window expanded.The slide is then tightened and the marks made.Similarly, on the longer side, the subtraction of 4" from10" leads to a presetting of the slide at one half of the 6"remainder, or at the 3" mark. Having split the 3⁄4" fractioninto two we find that the slide should be moved 3⁄8" backtoward the pencil point and tightened. Once the secondset of lines is scribed the opening can be checked foraccuracy.

Confining the marks to the corner areas lessens theamount of erasing which must be done. If the opening is

to be raised above the center, it can be lined out asdescribed and moved up. If it is to be moved up 1⁄2", a setof marks should be made on the vertical lines which are

1⁄4" above the old hori-zontal marks on boththe top and the bot-tom. It must beremembered that 1⁄4" isbeing subtracted from

the top and 1⁄4" is being added to the bottom to create thedesired difference of 1⁄2" between the top and bottom.

Another factor to consider in creating the opening isthe margins to be left around the design or the paper ifthe art is floated. In the latter case, a margin of 1⁄4" is aminimum that permits for safe movement of the art ifthe hinges become loosened in an accident. If the art isovermatted, the opening should maintain a similar dis-tance from the design, especially in the case of etchings.When etchings are printed, the paper is embossed by theetching plate and weakened at that point so that the matshould not press on the paper there. If there is a writtenlegend beneath the design which re q u i res a larger bord e r,the other borders can be made somewhat larger to avo i d

calling too much attention to the writ-ten material. As the size of the mat andw i n d ow grow, the margins allowe da round the designs should grow inp ro p o rtion. If the art is ove r m a t t e d ,the window should exceed the margina round the image by one inch on alls i d e s .

The tools for cutting windowsrange from simple knives to automatedmachines. The right tool will help toensure that clean, trim openings can bereadily produced. Aesthetics have a crit-ical role in preservation. If the workwhich surrounds the art looks haphaz-ard and imprecise, a viewer will not beas likely to notice problems which may

Figure 2

Preservation Matting for W


be present in the condition of the art. Older works maybenefit from antique treatments or patinas on the matwhich will compliment their age, but these too should bewell-crafted.

The bevel, a standard part of mat window design,has little precedent in the aesthetics of framing. Steps,ogees, and hollows are far more common elements inframes than any sort of flat incline. Bevels are powerfulfocusing elements, directing the eye into the opening.Indeed, too large a bevel may prove to be overpoweringto some works. The bevels handsomely dress the edge ofthe window. Also, it is easier to draw the blade throughthe board in the beveled position than it is to cutthrough in a line perpendicular to the plane of the board.This may be a function of the fact that more of the bladeis engaged in cutting fibers when the cut is beveled.

Any tool which uses a blade to cut windows willp l ow up the inner edge of the window into a profile (seefig. 2).This raised edge must be softened. A nail file cov-e red with industrial diamond can be an extremely usefultool for this job; sand paper or emery boards may leavegrit on the bevel contaminating it.

When six or eight ply boards arebeing cut, it is helpful to make the cutin more than one pass. Any attempt todrive the blade through in one passwill aggravate its tendency to drift out-ward as it rides up on the mass ofboard, resulting in “hooked” corners.If the blade is set shallow for the firstpass, it will cut a good track which canbe completed by setting it deeper forthe following pass. The overcuts willhave to be extended while cuttingthese thicker windows and it is safestto undercut this unfamiliar corner andcomplete the cut from the front.Before removing the window from thecutter, another sheet of board can beslipped underneath it to support the

window as it is turned to prevent premature dropout ofthe window and tears at the corners of the window.

When cutting windows, it is worth re m e m b e r i n gthat the board is expensive and the blades are not.Frequent changing of the blade can avoid tearing at thef ront of the cut. If such small disruptions on the faceof the window do occur, they can sometimes besmoothed out with the nail file by drawing it along theedge of the window in the direction opposite to that ofthe blade.The edge should then be burnished with abond folder. This will shave off some fibers and re p o s i-tion others.

This repair can only be done with board which has aconsistent color throughout. If a board has a colored fac-ing paper and a white core material, the use of a nail fileto dress any excess material out of the corners must bedone very carefully, since the file may bring some of thecolor from the facing paper and deposit it on the whitecorner. Small overcuts can be burnished down with abone folder, but serious ones require the cutting of a newwindow. If white glue is used to try to mend the largeovercut, it would represent a pollution of the window



since it may extend into the back sidewhere the window touches the art.

Each type of cutter has advantagesand drawbacks. The hand-held type canbe used to cut windows too large forother machines, but they will be slowerto use. Whichever is used, the bladeshould not be set to cut any deeper thannecessary to get cleanly through theboard. Setting the blade deeper meansthat more work is required to do noth-ing more than make cuts in the underly-ing board.

The underlying board can be madeof any long scrap. Paper mat is easier tocut than conservation quality board,making it a perfect candidate. Theunderlying board should be movedbetween each cut so that the blade willbe tracking in fresh material. The cutsshould be kept parallel to avoid the pos-sibility that the tip of the blade will be pulled into an oldtrack.

Hand-held cutters which have pivoting heads canproduce resultsequivalent to morecomplex cutterswhen they are used with a straight edge which has beenC-clamped at one end to the work table. Bar-type cutterscan be ideal for most custom framing needs and can beadapted for cutting oversized windows. To do this thewindow must be very lightly marked on its front sidewith the marks 1⁄16" outside the position they would haveif they were on the back. The mat is then fed in from theleft side so that it can fit inside the hinges which securethe cutting bar to the base (see fig. 3). The window is cutwithout any overcuts. Wall mounted cutters which aresemi or fully automatic can greatly facilitate productionand they can be adapted to meet the needs of cuttingcustom windows of varying dimensions.

When the linen tape is applied tocreate the hinge between the backmatand the window, both parts of themat must be coplanar and snuglybutted against one another (see fig.4). Any gap here will produce a spinewhich is unacceptably loose. The tapeis best activated with warm water andit should be dried in the closed posi-tion to ensure proper alignmentbetween window and backmats. Themat should be made large enoughthat the tape will not touch the art.When it is finished, the edges of thewindow and backmats should beeven, especially on the bottom. Thiswill maximize support and eliminatethe possibility that the boards couldshift or that the window could bebearing the weight. It should beremembered that the window is much

weaker than the backmat. This is one of the reasons whythe art must always be hinged to the backmat and notthe window.

The creationof more complexmats, ones with

more than one opening or more than one layer, mustmaintain the safeguards to be observed for ordinary mats.If more than one window is being cut in a single mat, thewindows must be placed far apart enough so that the artwill not overlap and create the possibility of one sheetembossing its neighbor. To create a sense of visual conti-nuity, pictures of people can be matted side by side whilelandscapes can be matted one over another to eliminateconfusion. If openings are being cut for materials whichare not all the same size or which will be placed in posi-tions which are not symmetrical, the marking of the win-dow must be done so that the windows are reversed, leftto right, as they are being marked on the back of the

Figure 4

Figure 3

Preservation Matting for

board. This is a factwhich is too easy to over-look and it must be firm-ly impressed on everyonewho cuts to avoid costlymistakes.

Double mats can beuseful both aestheticallyand as a means ofincreasing separationbetween the glazing andthe art. They should bemade so that the outsideedges of the windows have exactly the same dimensionsso that the window and backmat can be securely linentaped together. This can be simply done with the aid ofstrips of acrylic sheet which have varying thicknesses.These strips, called layout blocks, may be a few incheslong and 1⁄8", 3⁄16" and 1⁄4" thick to permit the creation ofthose intervals. The outer window is drawn out with therequired interval factored in and is cut to that size. It isthen laid face down on the back of the inner mat andheld securely there while the layout block is set downtwice in each corner so that a pencil can be run along itsinside to create the cutting lines for the inner mat (seefig. 5). Once the inner mat has been cut and its edgeserased and softened, the two can be glued together.

Since the windows which have been combined toform this mat will have the same outer dimensions, thedouble mat can be securely spined to its backmat. Thebackmat will have to be raised by another piece of boardunderneath it to keep the surfaces coplanar and allow fora tight hinge. This type of mat requires the use of two ormore whole pieces of board and becomes expensive. Oneoption for lowering the cost is the mixture of ordinarypaper mats with conservation quality windows. This maybe acceptable if the window nearest the art is of conserva-tion quality and the interval between its bevel and that ofthe nearest paper mat is 1⁄4". A study of the oxidation pat-terns created by poor quality mats will reveal that the dis-

coloration tends tofade off in the first1⁄8" and a 1⁄4" inter-val should givesome allowance forprotection. Still,the presence of theunrefined groundwood in the framemay be problemat-ic, and so this eco-nomic compro-mise cannot be

recommended when preservation is important.Certain works have designs on both their front,

(recto), and back (verso), sides which may need to beexposed. The opening in the backmat creates a hazardoussituation in that the paper artwork is vulnerable to punc-tures in that area. This is a greater concern when the artis stored in a box. Permanently framed items will be pro-tected from punctures if they are glazed on both sideswith a shatterproof material. The use of unlaminatedglass on the back of a recto/verso mat should be avoided.The windows in a recto/verso mat will be cut in the ordi-nary fashion; it is the placement of the window in thebackmat which poses the problem.

The verso window should be kept as small as possi-ble. If the work is to be overmatted on the front, and ithas a small area such as a signature which needs to beexposed on the back, the window in the front mat can belightly marked out with its lines extended beyond theirnormal dimensions. The work can be laid face down onthe mat with the parts of the lines which appear beyondthe work used as guides for placement (see fig. 6). Thedistances from the design which is to be exposed to eachof the edges of the mat should be measured and markedonto the backmat. It is critical to remember that themarkings must be left to right reversed if the design isnot centered horizontally. Once the back window hasbeen cut both windows can be spined with linen tape

Figure 5




and the work secured. If greater accuracy of

placement for the windowin the backmat is needed,another approach may beused. This involves cuttingout the front window andplacing the work, in properalignment, between it andthe uncut back window. Ifthe work does not containfriable media, the drop out can be laid back into theopening and the entire package carefully placed in a stifffolder and turned over, with attention paid to ensure thatnothing slips. The folder can then be opened and thebackmat very carefully lifted to reveal the work in placeon the front window, drop out combination. The mark-ing can be done as described before.

If the work is to be floated in the front window, thelocation of the back window is simpler because the marksto outline the window will be larger than the work beingmatted and it can therefore be laid face down on theuncut window and located within the marks. This is onlypossible if the design is not friable. The opening is mea-sured as before. The folded hinges needed to float thework must be made to cover less of the surface of thebackmat if the verso opening comes anywhere them sothat they will not overlap the edge of that opening andbe exposed to view. In all recto/verso matting, thedropout from the verso window should be saved so it canbe set in place when the hinging (or other attachment) isbeing made.

The one type of recto/verso mat which presents pro-found hinging problems is the window in which bothsides of the work are to be floated. Work which requiresthis degree of exposure will have designs on both sideswhich extend to the edges, and finding open space forthe hinges on the back of the work may be difficult tobegin with. The entire weight of the work will be bornby the hinges, both when the artwork is on the wall and

when it is lying ona table, and somore hinges thanusual will be need-ed. This type ofmat must be han-dled with theutmost care whenit is outside aframe, since thework is vulnerable

to puncture and to flapping in air currents if it is movedrapidly. If the work is stored out of the frame for anylength of time, secure a sheet of polyester to the inside ofthe back window. This can be done with archival gradePVA glue if the edges of the polyester have been sandedfirst. The hinges will have to extend beyond the sheet sothat they can be attached to the mat and this will notwork if the design on the back is friable.

If a six or eight ply mat is needed and boards of thatthickness are not available, they can be laminated fromthinner material. The simplest and cheapest adhesive touse for this purpose is starch paste. Starch is much lessexpensive than pure PVA and it will not dry so fast as tomake the lamination process difficult. If any starch isaccidentally applied to the front of the mat, it will notstick to the glazing as the PVA will. The starch will alsohave a higher moisture content and will require moretime to dry. Thus, it is useful to do this lamination at atime, such as Friday or Saturday evening, when the boardcan be left under weight for a few days without getting inthe way.

The paste should be cooked as usual but a muchgreater quantity will be needed; more than one cup perlamination. The paste can be poured into an old plasticfive-sided frame which will serve as a rolling pan. A cleanpaint roller is then used to roll the paste onto one of theboards in a fairly generous layer. The second board iscarefully aligned with the pasted board along their short-er ends and is pressed down onto it. A flat weight should

Figure 6

be placed on the laminatedboards and left undisturbed forat least an hour. When the initialtack has been established, theboard can be more aggressivelydried. This can be done by sand-wiching it between blotters ordry sheets of matboard which arechanged periodically. It may bepossible to cut the desired window board out and to dryit in a dry mount press, but care must be taken to ensurethat any boards which are glued together in this manneror used as double matting have dried fully before they areused in the frame. The use of pressure-sensitive adhesivesfor attaching or laminating boards introduces a type ofmaterial into the frame package which is not a usual con-stituent of the board, and violates the concept of keepingthe preservation package as simple as possible.

There are other options for deepening the windowwhich make more efficient use of materials. The simplestof these is the shim mat, in which a window which hasbeen cut to theappropriatedimensionreceives a lining ofboard which istucked behind theedge of the bevel.This can be donewith full sheets ofconservation qual-ity board or withstrips of the sameboard. In the former case, since the shim will not show, aboard which is chemically appropriate but which may bean off color can save money. If strips of conservationquality board are used, they can be applied in a pinwheelfashion to facilitate assembly (see fig. 7). If the stripmethod is used in a situation in which it would overlapthe edges of the art, it should include a two ply liner

which gives the back of thewindow an unbroken surface.

There are times when it isbest to pull the shim awayfrom the edge of the bevel. Adrawing which is degraded atits edges or a photographwhich is heavily cockled at itsouter margins are cases in

which pressure should not be applied to the art. A shimwhich is designed so that it sits outside the edges of theart can relieve this pressure.

The normal pressure which a window mat applies tothe edges of the artwork is useful in most cases in that ithelps to hold the sheet in place. A window design whichincreases the depth of the window without the expense ofadding whole pieces of board can be created through theuse of strips of conservation quality board which havebeen cut so that they have two bevels.

If the strips are cut so that one of the long sides ofeach is

beveled,and one of theshort ends ofeach is alsobeveled in anorientationopposite to thebevel of thelong sides (seefig. 8), thesepieces can befitted onto the

back of the window to create an extension of its bevel. The window must be cut with its opening enlarged

by 1⁄8" in height and width to account for the spacerequired by the extensions. The extensions are then cutand fitted in a pinwheel fashion with each extendingfrom one corner of the window and passing beyond theopposite corner on that side. To ensure that there is no

Figure 7

Figure 8



Preservation Matting for gapping at the corners, theb e vels on the short sidescan be cut so that theangle which their edgesmakes with the long edgesis slightly less than 90d e g rees. Thus, there willbe a slight gap when thepieces are assembled onthe back of the window (see fig. 9). This and the seamswhich separate each of the bevel extension strips re q u i rethat the mat be lined with at least a two ply cover if it isovermatting the art. The beauty of this technique comesf rom the fact that if the beve lextensions are made of the sameb o a rd as the window and are fittedtogether well they are indistin-guishable in the frame from a matof an equivalent number of plyswhich was laminated and cutt h rough ord i n a r i l y.

If either this mat or the shimmat mentioned before overlapsthe edges of the art, each willneed a lining of two ply board. Tomake this type of facing, cut a piece of two ply which hasthe same outer dimensions as the mat, and lay both onthe work surface with the two plyon the bottom and the mat, faceup, on top. Marks that start at thecorners of the window and proceedtoward the center of the windowcan then be cut onto the surface ofthe two ply (see fig.10). (Makingthese marks with a pencil mightleave graphite on the window.) Thetwo ply can then be removed andgraphite crossover lines can bedrawn just outside the cut marks(see fig.11). A mat cutter can then be used to cut out the

window denoted bythese crossover lines.The two ply can befitted onto the backof the window toensure that it coversthe back but does notshow through theopening. If it does

show, it should be enlarged before it is attached to theback of the window. If it fits, it can be glued in place.Since it comprises a reverse beveled window, it will havean edge which will be easy to hide behind the opening in

the front window and willrequire little softening andclean up.

Both the shim mat andthe extended bevel mat aremade entirely of conserva-tion quality board and thuscan be rather heavy. Othermats can be made withadded strips of board toform their exposed verticalsurfaces or their bevels and

which can be filled with acid-free corrugated board.These mats have the advantage of being lightweight and

make the frame lesscumbersome to handle.A mat package or framewhich is heavy will notencourage those han-dling it to use the light-est possible movements.

The simplest ofthese mats has wallswhich are perpendicularto the surface of the matitself. This type of open-

ing can be especially useful when a small object is being

Figure 10

Figure 11

Figure 9

matted with a document.Because the opening lacksa bevel, it will not drawundue attention to theobject and away from thedocument. The openingwhich is to have the wallsshould be made somewhatlarger than normal to com-pensate for the shadowswhich will be cast. Theadded depth needed will depend on the height of thewalls. In general the expansion should equal the wallheight.

Once the mat has been cut, strips of the same boardcan be adhered to the edges of the opening in a pinwheel

pattern (see fig. 12).Acid-free corrugatedboard can be used tofill the area aroundthis opening to addsupport. The docu-ment will be housedunder the surface ofthe window’s otheropening and willrequire a built-up

platform of conservation quality board on top of acid-free corrugated (see fig. 13). This two-level mat allowseach item to be secured to the backmat in the ordinarymanner.

Deep mats, those which have added bevels and light-

Figure 12



weight cores, can maintain the beneficial physics of the tra-ditional window while providing as much space as may beneeded between the surface of the art and the glazing.Id e a l l y, such a mat should contain only time-testeda rc h i val materials and should make the most economicaluse of the materials so the labor re q u i red can be adequatelyrew a rded. One such mat can be made by affixing care f u l l ycut bevel strips to the back edge of an appro p r i a t e l yenlarged window and filling the space in back witha rc h i val corrugated board and a two ply cove r i n g .

The geometry of sucha deepened window is thefirst problem which mustbe mastered. Since thebevel will be added to theback of the window, it isnecessary to calculate both the factor needed for enlarg-ing of the opening and the width of the bevel itself. If themat is viewed in cross-section, the problem can be visual-ized as a right triangle in whichthe depth to be added is A, theexpansion needed is B, and thebevel is C (see fig.14). If the legsof the triangle (A and B) can bemade equal, the job is simpli-fied. In a right triangle in whichthe legs are equal, the oppositeangles are also equal and mea-sure 45 degrees. A mat cutter which cuts at a 45 degreeangle will thus create the simplest bevels to work with. Ifthe cutters available cut at some other angle, there areeffective and inexpensive hand-held cutters on the marketwhich will produce 45 degree cuts.

To determine the amount of space needed to separatethe surface of the art from the glazing, one can lay the arton a flat surface and stand a transparent plastic ruler next

to it to sight the highest point in the art. A mat of this type can be made in any thickness, but

in practice there are some dimensions which are especial-ly useful since they will accommodate one, two, or threelayers of acid-free corrugated filler board evenly. If a deepmat is made with a depth which exceeds 1⁄2" the bevel willbe such a prominent visual element—focusing the eye onthe inside of the window—that it may detract from theenjoyment of the work being matted. If a depth of 1⁄8" isneeded, the window will be expanded by 1⁄4" (1⁄8" per side)

and the bevel can be cut with awidth of 3⁄16". To produce adepth of 1⁄4", the window willneed to be expanded by 1⁄2" andthe bevel can be cut 3⁄8" wide.For a 3⁄8" deep mat the expansion

will be 3⁄4" and the bevel can be cut 1⁄2" wide.To create the strips, a long piece of the approximately

board should have pencil marks placed at either end (seefig.15). The section of theboard nearest the edge willnot have two bevelededges and should be dis-carded. (If this section isgiven a different size fromthe others it will be easierto distinguish when theyhave all been cut.) The

cutting head can be aligned so that the cuts will go rightthrough the pencil marks or, if a bar-type cutter is used,the edge of the bar can be aligned to meet the marks. Ineither case, it is very important to en s u re that the cuts bespaced as evenly and accurately as possible. If the strips allmatch, assembly will be much easier and more accurate.Once the cuts have been made, consideration can beg i ven to the shape of the end of each strip which will per-

Figure 13

Figure 14

Figure 15


mit creation of the beve l .Since each of the strips will be set at a 45 degree

angle to the window, the angle of their intersection with

each other presents a complicated geometry problem.Fortunately, if the angle of 55 degrees is used itwill be close enough to the exact answer toyield a completely useful result. To achieve thisshape for the ends of the strips, a protractorshould be laid along the edge of the board orone of the cuts and an angle of 55 degreesshould be marked and lined across them (seefig. 16). This can be done before or after the parallel cutshave been made. The cutter should now be used to cutthrough the strips along this line. Care must be taken toensure that the strips do not shift during the cutting

process. A piece of drafting tape can be used to holdthem together during the cutting. This tape will be onthe back of the strips and can be removed as soon as thecutting is complete to avoid contamination.

If the cutting has gone according to plan, the result-ing strips will have two faces on their front sides (see fig.17) and three faces on their back sides (see fig. 18). Sincethe manipulation of the strips may be somewhat confus-ing, it can be helpful to keep a model strip handy whichhas each of its faces labeled, keeping in mind that the topdenotes the surface which will be bonded to the back side

of the window and the bottom will be nearest the back-mat while the end will butt against the neighboringbevel. The creation of the bevel strips may require someset up time, and it can be useful to cut extra strips of themost appropriate colors for storage in a drawer to speedthe production of future deep windows.

In laying out the window, it is essential to rememberthat the presence of the bevel will require a larger open-ing. If an 8 x 10 inch work was being float matted with a1⁄4" float and a 1⁄4"deep bevel, the opening would need tobe 9 x 11 inches, with 1⁄2" for the float and 1⁄2" for thebevel. This is one of those facts which is annoyingly easy

to forget and should, perhaps, be noted on a folder whichis used to store the model strip and extra strips to serve asa reminder.

The assembly of the window requires some practice.Any graphite markings which may remain fromthe cutting of the window or the strips shouldbe erased with a white vinyl eraser—not to pro-tect the art, but to avoid the possibility of thegraphite showing up on the finished product.The strips will be glued to the back of the

opening with archival PVA glue. (This should be checkedto ensure that it has not begun to degrade. This degrada-tion can be detected by the vinegar-like odor producedby the breakdown of the acetate.) The glue should beplaced in a plastic squeeze bottle which will permit theapplication of a uniform bead of glue along the length ofthe surface to which the strip is being bonded. These bot-tles have quite a tendency to get clogged as the glue driesin their nozzles. A useful antidote to this problem is a capwhich comprises a long spike of soft plastic (as can befound in the bristles of some hair brushes) which has

Figure 17

Figure 16

Figure 18



been welded with a hot melt glueto the inside of a plastic cap, as inthis cross-sectional diagram (seefig. 19).

Before the actual mat isassembled, a small model shouldbe built to familiarize the matmaker with the assembly process.This can be bonded with linentape so that it will fold flat andcan be used for future referenceand as a teaching aid. Each strip

will be aligned so that the end which contains the 55degree angle will meet one of the corners of the window(see fig. 20).

The most important part of the assembly is the situa-tion of the strip along the edge of the window. This iscomplicated by the fact that the bevel creates an overhangwhich obscures the joint of strip to window edge. Tofacilitate the viewing of that area, a strip of mirror withdulled edges can be placed under the window so that itoverlaps the opening and reflects the edge being workedon. Alternately, the window can be aligned so that the

Figure 19

Figure 20



Preservation Matting for strip which is being appliedis perpendicular to the edgeof the work table and themat maker can look underit (see fig. 21).

A bead of PVA isapplied to the back of thewindow, near but not touchingthe back of the bevel. This beadis then smoothed out using atool or a finger and the strip isset on the glued area. This mustbe done promptly since the gluewill dry rapidly. The strip can belifted and repositioned duringthe first minute, but any excessglue which oozes out of the jointshould be left in place to dry.This glue can be shaved orscraped off when it is dry with asharp blade. The archival PVAwill aid in assembly since it willbond so quickly that it can serveas a contact cement and the stripshould stay in place once it hasbeen pressed down. The mat cannow be rotated for theapplication of the second strip.This should be done so that thenext strip can begin at a corner and will pass the firststrip at the far end of that side (see fig. 22). Wo rking inthis manner means that the first three strips can bealigned to the corners where their application will beginwithout any obstruction. In the case of the fourth strip,the corner at which its application begins will already beoccupied by the first strip and the final strip will haveto fit in under it. The bead of glue which is applied forthe last strip will have to be smoothed in the area ove r-hung by the first strip with a tool since a finger will notfit in this space.

When all ofthe strips havebeen set in place, abead of PVA canbe run along theback of each at thepoint where they

join the window. This willreinforce this joint. Theproperly aligned strip willbe slightly behind or willcome just up to the bevel,but it should not have anyof its bottom portionshowing. Lifting the matwhile the strips are notfully dry risks dislodgingthem. If the mat is laid onan old scrap of acrylic sheetboth can be lifted togetherand the mat will stay inplace. If any of the strips isfound to be intrudingbeyond the bevel of thewindow, a blade can beslipped in between thebottom of the strip andthe window in the intrud-ing portion and the two

cut apart. A fresh coat of glue can be applied to the sepa-rated portion with a brush and the strip can be re-attached. The resulting structure will now look like theitem in figure 23.

The corners must be aligned, adhered and reinforced.This is done by first trimming the excess portion of eachstrip with a razor blade using smooth sawing motions sothat its end is in plane with the end of the neighboringstrip. Glue is carefully brushed onto the end of the stripwhich was cut at 55 degrees and the two ends are pressedtogether with attention paid to ensure that their bottoms

Figure 21

Figure 22

Figure 23

Works of Art on Papermatch (see fig. 24). A pieceof linen tape will help tohold the ends as they dryand will provide addedstrength throughout the lifeof the mat. This can bemade from a 11⁄2" piece oftape which has been splitso it is 1⁄2" wide. If thispiece is cut at the center ofone of its long sides, it canbe adhered first to the sidewhich was recentlytrimmed and drawn tightaround the corner andapplied to the other side. Ifthe end of the split in thetape meets the bottom ofthe outside corner, the tapecan also be applied to theback of the window (seefig. 25).

When the glue and thetapes have dried, the matwill begin to have enoughstrength to be more readilyhandled. The area aroundthe bevel can now be filledwith acid-free corrugatedboard. The board can be glued into the space in a pin-wheel pattern. If more than one layer of board is used,the direction of the pinwheel should be reversed witheach successive layer so that the ends will overlap thejoint of the layer beneath. If the work is being floated,the window will be finished once all its components havedried. If this window is to be used to overmat the work,it must be finished in the back with a two ply facing asdescribed before. The glue used to bond this two plyshould only be applied to the corrugated board and cannever be allowed to seep onto the exposed portion of the

bevel where it could contaminatethe art. The finished product willlook like the cross-section (seefig. 26).

There are some forms of win-dows which lack the traditionalbevel. The straight cut opening issometimes used for aesthetic rea-sons and can be an element inwindow designs which supportthe work being housed. The pri-mary problem with such a win-dow is the creation of cleanedges and corners. As has beennoted, it is much easier to makea beveled cut; cutting throughthe board perpendicular to itssurface requires more force. Thethicker blades found in utilityknives are appropriate for thistask, but they must be thorough-ly cleaned of the oil in whichthey are packed to prevent rust.

Since this window openingwill have the same dimensions onboth sides and will not requireany overcuts, it can be markedon either the front or back of thewindow. The cutting process will

plow up some of the board and the choice of whether theopening is cut from the front or the back will depend onindividual cutting habits and the quality of the materialunderlying the cut. To get a smooth, even edge to theback of the cut, the material under the board should berigid enough to keep the board from bending downwardas the knife comes through. Scrap acrylic sheet can bevery useful here and for other, similar cutting jobs.Whichever side is to be used as the front of the mat, thecutting should not be attempted in a single motion.

All cutting of resistant material is best done in several

Figure 25

Figure 24

Figure 26


Preservation Matting for passes, with the first pass being a light, guide cut. In thiscase, a straight edge should be laid along the line to becut and the cuts should start at the corners and proceedto the centers of each side. The point of the utility knifecan be used to carve clean crisp corners, and if anystrands of board are created by the cuts not havingaligned perfectly, they can be removed with a nail file.The back of the window will not be in full view, and itcan be rounded and softened with a nail file to make itless abrasive.

Other circumstances may require the use of a win-dow with a reverse bevel. This type of opening has theadvantage of presenting an accommodating edge to theart. This may be useful in cases in which there is some

disfigurement near the edge which should be covered inordinary viewing but which needs to be seen at times.The reverse bevel is easiest to cut from the front of themat. The opening should be marked as lightly in graphiteas possible and cut without any crossovers. This meansthat the cutting will have to be completed by cutting thecorners with a blade, but this can be easily done sincenone of the cutting will show up in front.

If the work being matted has an outline which isirregular, and that irregularity is important to the appre-ciation of the work, it may be necessary to cut a windowwhich is not rectangular. If the work is being floated inthe window this task is simple. The work can be mea-sured as if it were a rectangle, using its largest dimensions

and the marks laid out as usual on theback of the window. The work can becentered, face down, between thesemarks and a clear plastic ruler laidalong the irregular sides so that themarks there can be adjusted. This can-not be done if the medium in whichthe design has been executed is, friablesince it could not safely be laid facedown on the mat. The cutting of suchnon-rectangular openings may requiresomewhat smaller crossovers thanusual.

Circular and oval opening mats canbe cut with mechanical cutters, butthey are surprisingly easy to cut byhand when such machines are notavailable. The single-edge razor bladewith a reinforced backing can be drawnthrough the board to make beveled cutswithout too much effort. A circularopening can be marked with a compasson the front of the window with themarks set 1⁄16" further out than the sizerequired to compensate for the fact thatthe window is being cut from the front.

A piece of polystyrene foamboard can be placed under themat, the blade eased into themark, and then held at theproper angle as it is drawnalong the line and the board isrotated. It the cut is less thantrue to the line, the excessmaterial can be shaved off witha fresh blade and the bevel canbe cleaned up with a nail file.The lack of any corners makesthe dressing of the bevel easierthan in the case of a rectangularopening.

Drawing an oval requiresmore effort. The long and shortaxis of the oval should be drawnon the face of the window with1⁄16" added to the ends of each(again, as compensation for thefact that the cutting is beingdone from the front). A com-pass point is set at the spot atwhich the axis intersect and theother end of the compass ispositioned so that it falls at theend of the long axis. The com-pass point is not set at the endsof the short axis and marks arestruck at the point at which it meets the long axis (seefig. 27). Push pins are stuck into these focal points and apiece of string is tied so that it creates a triangle compris-ing the pins and one of the ends of the short axis (see fig.28). A pencil is set inside the loop of string and rotatedto inscribe the desired oval.

The cutting can be done as with the circle. Sincethere are flatter parts of the oval, these are good places atwhich to insert the point of the blade. More of the bladecan be inserted through the board while cutting these

flatter portions and onlythe corner of the bladeused to cut the moresharply curved portions.This permits a steadier cutin the less curved areas andmore mobility in thetighter curves. More com-plex shapes can be cut asopenings, but the increas-ing elaboration of theshape can begin to com-pete with the work beingmatted.

If the object beingmatted is thicker thanordinary paper, a sink willbe needed in the mat toaccommodate this thick-ness. The subject of sinkswas treated in thePreservation Supplement(PFM February 1995) buta discussion of mattingrequires some review andupdating of this issue. Thesink can be made of stripsof conservation qualityboard which are attachedto the backmat or it can

be made as a separate window which is spined along thesame edge as the face mat. Its thickness should be equalto the object being matted and it should provide spacefor hinges to be attached to the backmat if they are to beused. All sinks need a tab which will allow the art to beraised from the sink without a tool. This tab lies underthe art and is pasted to the backmat or is glued under theedge of the sink.

If the opening of the sink is made to be close in sizeto that of the work being matted, it is possible to elimi-

Figure 28

Figure 27



Preservation Matting for nate the use of hinges. Ifthe sink were too closeto the size of the mattedwork, however, theremay be insufficientroom for expansion dur-ing periods of elevatedhumidity. A gap can bebuilt into the sink if it isfilled with soft tissue. Todo this, the work shouldbe laid on a sheet of con-servation quality paperand the position of itscorners marked on thepaper. The paper is thencut so that flaps areformed which intersect atthese points (see fig. 29).The flaps are then foldedover the edges of thework and it is set in thesink. Rolls of tissue arefitted around its edgesand the flaps folded outonto the surface of thesink. The presence ofthis four flap folderensures that the rolls oftissue cannot get caughtin any irregular portionsof the edge of the workbeing matted.

If the sink is madeof a wall of four plyboard which has beensurrounded by fillerpieces of acid-free corru-gated board with a gap in between, tabs of linen tape canbe threaded through slits in the backmat which have

been cut in that gap (see fig. 30).The tabs are then taped to theback of the backmat. The inclusionof the four-flap folder under theartwork makes the addition of alifting tab unnecessary.

Works on boards which havewarped require a sink which canprovide very delicate support. Atechnique for making such a sinkwas outlined in the PreservationSupplement (PFM February 1995)but that method did not provideas much stability for the object aspossible, since the points at whichthe object was held were limited.A simpler and more stable supportcan be made from a sheet of con-servation quality paper and a sinkof appropriate dimensions.

The use of acid-free corrugat-ed board to create this sink allowsfor the ready creation of differentlevels in the surface of the sink.

This is done through the compres-sion of the board through cuttingaway some of its layers. The pres-ence of varying levels in the surfaceof the sink. This permits moreaccurate attachment of the elementsused to secure the work in the sink:straps created by portions of anunderlying sheet of paper which hasbeen cut to fit the object beingmatted (see fig. 31). The straps atthe corners are folded across theobject and threaded through oneanother, and the object is then set

into the sink and those straps are secured to the edges ofthe sink with linen tape. The radiating strips of the sup-

Figure 29

Figure 31

Figure 30

port sheet can thenbe gently puffedsnug and secured tothe sink with linentape, creating a con-forming sling (seefig. 32).

Other designswhich provide sup-port for rigidobjects may be con-sidered either sinksor windows, sincethey share charac-teristics of both.One of the simplestis a support for col-lectibles. Theseitems are especiallydifficult to housesince even the addi-tion of Japanese tis-sue hinges withpaste may affecttheir value.

Items such assports cards mayneed to have bothsides shown and acombination of twoply conservationboard and polyestersheet can accomplish this. Two sheets of polyester shouldbe cut so that they are each larger than the opening ofthe window. A window which has dimensions slightlysmaller than those of the two ply window should be cutin its outer edges. The edges of the polyester windowshould be sanded. The outer edges of the other sheet ofpolyester should also be sanded, and it should be cleanedand bonded to the back of the two ply window with

archival PVA glue. The artcan be laid into the open-ing once the glue is thor-oughly dried. The poly-ester window can be fittedonto the front side of thetwo ply and secured withstrips of linen tape whichare burnished so that theadhesive on the tapereaches the two plythrough the slits (see fig.33).

Even the bevel of awindow can be used as asupport for rigid objects.A small object which isnot delicate can be fittedwith a four flap folder ofstrong Japanese tissue. Aneight ply window canthen be cut so that theedges of the object will fitonto the bevel of the win-dow if it is placed inside.The four flap is foldedaround the object andweighted in place and thewindow is fitted over thiscombination with thebevel inverted so that itsedges touch the wrapped

edges of the object. The flaps are pulled gently throughthe opening of the window and secured to the front ofthe support mat with linen tape using equal tension onall sides (see fig. 34). The object should now be steadilysupported and can be fitted with a covering window matand framed.

A window mat can protect a work of art from dam-age caused by handling. It can provide steady restraint of

Figure 33

Figure 32



the edges of a work which it houses to mitigate theeffects of variations in climate. It can cradle an objectwhich is warped or degraded and weakened. When theedges of the window cover some of a design, they cankeep that area from fading and can give us a hint of whatthe coloration of the whole design looked like originally.Similarly, the portions of the paper which the windowcovers will be protected from the damage exposure tolight brings, and will serve to show the original color ofthe sheet.

The window mat evolved from the volume page, andwill continue to evolve. The possibility of improved win-dow mat designs which may support works of art and

artifacts without changing them in any way is one of thegreat challenges facing preservation. Japanese tissue andvegetable starch hinges represent the minimum of changewhich can be accepted when an object cannot be sup-ported by its edges, but increased use of overmatting andsupport from edge strips and other properly designedwindows can eliminate the temptation to use hingingmaterials which may cause changes in the art as they age.

Advances in matting protect the framer and the workbeing framed. They elevate the role of the framer, as theydemonstrate their ability to maintain materials which willbe important to the future.


Preservation Matting for - Library of Congressmost of the preservation functions that the bound...

Documents

Transcript of Preservation Matting for - Library of Congressmost of the preservation functions that the bound...