162 E_=/lictrciotrcy .7lclhd 01 J)WfrO~~l7g’ fiats.

ten tl,nci its wciglit of wntcr, is llicll poured on it by dC~gWCS, and the &olc bror~,ght to a boilin, (1. heat iu 2~ leach vessel; beltlg cureful to &[J th? aclti mixture and the fed& or potatoes, dl Stirred together, anti to make the additions in such mall quantities, as to interrupt the ebullition as little as possible. Two or three minutes after the lasl; addition has been ma&+ the starch is completely sac-

cbarizetl; tl~c xsscl must tlicn be tnken off’ the lit-e; without ~hiclr prccaulion thr: WCcli;irirlC lllilttcr W0l:lt.l VcPf SO011 bCCOUlC SCOiChct].

Tlic mixture is then ailonecl to cool ptij-! :;r~rl tl:lril:g this time the II~~~IY~CIIIOY~C ILC~I~ is I:Oilrc(l tlpO:l tl~e nl:inl;tl charcoul by small portions al: n tinlC, 2nd stied witlr,:l v;ootlen sp:It!Il:I; and t.lli:j part of the process is linislretl, by miltir!g this charcoal in the S~ccllarine liquid and acid, when the salphuric acid acts with as much energy as in Ihe former process.

This mixture is then boiled to a rather thick consistence, and is passed throug$ a colour-mill. The mill is previously w&2tl, by throwing into the hopper the remainder of the acid liquid or vinrp,

and then pure water; anti these widlir\gs arc put into ihe blacking; findlyl, the 0th inyctlicuts arc ad~letl, togc~licr with a suhicieut quantiiy of wttcr, lo inwxtsc its volurnc to 17 litrcs and a half, as in the liwnier process.

‘The blaclti~!g thus oldaid is absolutely the same RS the other: the fincnrss ol the black, l%hich cntcrs into the composition, is even more equal.

WC also find, in commerce, many other kinds of blacking, formed of ITsinS, gum-hc, Spirit of wine (alcohol,) lamp-black, ivory-black,

anti other substances, in great number, and in various proportions; but they are very little used. I’.

[Diclionnuire Technologipue.

IN, or near thC pl2ces ~rcqucnfd by these vermin, place upon 3 slate or tile, one Or two mcnt spoonfuls of dry oat meal; I;ry it thin, and prcsS it flat, ihnt jwu may more wsily know what is taken away_ The rats, if not i~ltcrrul)lcd;;,iii c01ix regrilnrly to feet1 there; snp- ply them thus with frdl oiItrrtca1 for two or three days; Ihcn, to about six spoonfuls of tlrp oatw~~~ and having stirrctl the

cLdlr atlrl Ihrec drops of oil ot’a&ecds; n;isturc wc:II together, feed them with this for

two OL’ thrCC tliLyS more; then for one day give them only half the quantity they hVC Mu:lliy +tcll 0T this sccx~tetl oatmeal, &I ou the

followi~ig day, place the following misture: TO four ounces of dry ontrncd, scented with Six drops of oil of

anise&, add half an ounce of carbonate of barytcs, prcvioiisly pounded wry fine in a mortar, nntl siftetl through il. little fine muslin or camlh: mix this intiumtcly with the scenleL[ oatmca], illlti i;ly

On the PrtyClraliotL Of Gdtl, lllltl lll(i Urt of CiJflirrg ilb size, oil, cvc.

WE have already given 3. description of the mode pursued jn France, in the Ynrioiis kinds Of gilding 1l~Itlll metals, wd, 2nd other substances, and now prcscut a view of the English pructice,in some of the processes of this art, ES given in Gill’s Technicul I&e- pository.

The art of giZ&ag, or layin, (7 8 thin superficial coating of gold, on wood, and other substances, has been long practisctl and highly cstccmcd, both for its utility and the spicutiiti effect which it pro- tluccs. Gold, from its great beauty? n~~tl from he lenglh of tirnc, tlurina whidi il may Ix c3pose(l to Ihe adtion of the air, without t.arnishiLtg, is u~~q~~cstion~~bly the most v;tlrra.ble of all ~~~bstsn~es, tin the puqioses of ticcxtration: but, on account ol’ ‘1s gwnt pin: and wei$t, it call only 13,: ;Iwtl for pn::rai p!lrpoSW~ Ill the siI;!i!C: Oi’ iL

t\lirl skin, or Ical; ‘ad it is usua!ly cnlitY1. (+oltl is tile IlllIst I~i::llc;t-

b[e and ductile of ;dl su!~si.unccs; :mrl therefwe, a givcl~ w(‘i,ght ol‘it, not\vithst:inding its high spwifc gravity, lllily, by I~~:lt~llg, be ~~l:ltlC to cover a larger su&ace than i1n qua1 quantity 0L ilny other body

I 64 On GiZiZitag in site, oil, ~$2.

degrees of thickness, and formed either of the pure metal, or of alloy of this with silver: second, as an amalgam of gold; and, third, in gold powder.

OF GOLD AMALGAM.

The amalgam of gold is made by heating in a crucible some pure quicksilver; and, when it is nearly in the boiling state, about the sixth part of its weight of fine gbld in thin plates, heated red hot,~s to be nnmersed in tt. The mixture soon becomes homogeneous; and then it is &owed ‘to cool. When cold, it is to be, put in a piece of soft leather; and, by gradual pressure, the fluid part of the amalgam, consisting almost wholly of mercury, ‘may be fwked through the pores of the leather; whde the gold, combined with about twice its weight of mercury, will remain behind, forming a mass, of the con- sistence of butter. This, after being bruised and ground in a mord tar, or shaken in a strong phial, with repeated portions of salt and water, till the water comes away quite clear and unsoiled, is fit for use,; and maybe kept for any length of titne, without injuring, in a corked phial.

It is of the utmost importance, that the materials of the amalgam, and especiaNy.the mercury, should be perfectly pure; as the I’east portion of lead or bismuth, would very materially injura the beauty of the gilding, by deteriorating the colour of the gold, and .filting it with black specks.

OF GOLD POWDER.

Gold in powder is prepared by three different methods: the first and most sim la is, to put into a glass or earthenware mortar, some gold leaf, wrt a little honey+ or tkick gum-water,* and to grind the *R mixture for a considerable trme, til! the gold is reduced to extremely minute fragments: when this is done, the honey or gum-water may be washed away, leaving the gold behind, in a minute pulverulent state. A more effectual and quicker method of reducing gold to a state of powder, is, to dissolve it in aqua Regia, or, as it is deno- minated in the new chemistry, in nitro-muriatic acid, and then pre- cipitate it with a piece of copper. The precipitate, after being digested in distilled vinegar, and then washed with, pure water and dried, is in the form of a very fine powder; and is said to work

??Loaf-sugar ground in the dry state with the leaf gold, and afterwards se- parated by washing, is preferred by some; we have used common niolaases, and have nat seen reason to wish for a better article. must, in any case, be aaed in the washing.

A large quantity of water &MT%

On Gilding in size, oii, &c. 165

better, and is litter for burnishing, than the powder obtained from leaf-gold. The very finest ground gold is produced by heatinggra- dually the gold amalgam, already described, in an open earthen ves- sel, and continuing it over the fire till the whole of the mercury is evaporated; taking care that the amalgam shall be constantly stirred with a rod of glass, to prevent the gold from adhering in lumps, as the mercury flies OK

the residual gold, \VIren the III~IYXII-~ is completely evaporated,

being then ground iu a IVedge\vood-ivare mortar, with a liltle water, and afterwards dried, is fit for use.

Gilding is performed either with or without heat. Rv the first of these methods, those substances are gilt which are not liable to al- teration, by exposure to a moderate bcut; such as, m~~nls, glass, and porcelain. l’he Sec01d l11elhd is pfilctketl With til(JSe substances, as wood, paper, Icnd, SX., which would bc tic~trtrycti 1)~ being raised to a teu~pcraturc rccluisile for d ~Gldiwg Iho li)l.llw~. Our busiiiess is chiefly witlk wd.

Gilcliilg 011 wood, bolh in oil aucl ~;IrliiA, is :it pr~~nt in its high- est perfectiou, a11t1 is csccu~~~l ill Lolltlou belter tilnrl ~II any other part of the worltl. ‘I’ll;lt \\llicil ri:i brougl~t l’rolu ~:IXIICC, and other parts of tlic colltirrent, is by no IncanS eclual t.0 it: not that it is to be inferred, frolic liencc, that gilding is well csecuted by all who uudertake it in tile metropolis. Mitlly IUCII, who have worked there all their lives, are uuable to gild properly a coinmon picture-frame, though they get cmp!oyo~cnt. it is however hoped, it belter judg- lnent will be f’ormed ii.0111 the instructions here given; from wllich it has been known, that a person brctl a cabiuet-maker, and who never saw gildiog performed, has accou>plished the work in the best style, in the course of six months’ practice.

RURSISIIED GILDISG ON WOOI).

To begin with picture-frames, or mauldings, which are the simplest works performed in this branch.- Put into an earthen pan, that will hold a quart, three half pints of strong size, the composition ofwhich will be described hereafter: make it very hot over the iire, but do not let it boil: add some of the best whiting, powdered fine; mix them with a brush kept for the purpose, or beat them up \?rith a piece of lath, 8.~. as au egg is beaten, till they become thorou$hly incor- porated, aud of the consistence of thick cream: put a little of this mixture, with an equal quantity of stron g size, iuto a smaller pan; heat it till near boiling; and, tith a stiff brush, lay it over the whole work, in order to clear away any dirt, b orease, or hand marks: this is called thin-whitening the WOTIC, and ruakes a ground for the other operations. When the wood, however, is very dirty, it is absolutely necessary to wash it all over the thin white is applied;

with a sponge, and hot water, before which precaution will prevent the cliipping-

up of the preparation. When burnished, the thin white should be particularly well dried: after which, the work is to receive four coals more of that composition which was roarlc ‘, as tlescribctl, of t11c COll-

&encc of cream, ivarmed, but 1101 milt,l~~ so hot :I% ti11, thiu whitening;

ItiG V:L (i;idiug- ifi, ,) izi’, oil, I$C

t&i,; cm that OIJC coat is dry, before another is applicil. iind here Jt is nCcessfiJ'y to obw'vc, oJJcc for ali, that, throughout this pr0CCss, 0ne coat must always bc dry, before another is lad On, dJ&!VCr Inay be the WnJposith used. ‘rhe sixth coat, ~vhcb is

also of thick while, must be laid on, by passing the brush in a smooth, even and flowing manner, over two feet in length Of the work at a time, in ortlcr to gnin a surfxe, and f:hcilitate the smoothing, here- ufter to be described. Before the whitening is dry, the fiat parts should be rubbed clown with a chisel, the hollows with ;i gouge, and the rounds with the fnger or fingers, as may be most cunvenient: should the hollo~vs be too lnrge fur a gouge, the finger. will answer every purpose. When dry, any superlluous whitening, that rnny have fdlen over the edges o’f’ the moultlings, kc. may be lightly pared off’ with a chisel or gouge, accordin g as the parts arc situated: then give it. ;I seventh CO&t, similar to the prcccding; anti it will be ready for smoothing, which should be performed in the foilowing manner:

Take some close-gained pumice-stone, and, with a Sash-SLW, (an old one will answer the purpose,) cut it into pieces, about three or four inches long, (if tbc work bf. very small, an inch, or an inch and a. half &fill do;) lit them to the diikrcnt niouldings, usil~g a rasp to form the rounds, al~tl a, gouge [or the hollows. The flats are to be xnade IJY rubbing the ]~eccS ot’ pUnlice-stone on a smooth flat stone, making their sides at right.-angles to each other, that they may smooth two si!ic5 id+ once. .I)uring these operations, the pumicc- stones mnst 1~: f’l’C!iUCIlil~ tiippcd in water. Lay the pieces thus prepxrcd in n iqc C’iiUlllW p:l Luil of water, not less than Tao clu;lrts; thrn t&e ;t hog’s-hair brush and R spngc, both of’ convcni- cant siws: dip the brush in wrztcr~ zntl WA about two feet in length of the work nt ;L time, t;Lkin~ the inouldings alternately: then with Chc pun&c-stone, nlrendy fitted, rub up and down, till a smooth sur!~:c:c is obtainctl: rcmovc the water with the brnsh? and squeeze it into tile pan: wi~ni: water remains maybe taken off~th the spoage, Ivhicb will coniplclc the SliJo0tl:i~lg of that part. Proceed in the Snllle mxnner Ivitll similiw porLions; for if too much be wetted at a time, the whitening 1wct~111es soft, ztnd unfit to bear the pumice-stone. ‘I’he frames must then bC Set asidc to dry.

fn carved work, tile \r,hitcning and smoothing differ somewhat from the preceding. A !tcr tire thin white is drJ, the coats thatfol- 10~ muSt be rather ~ed~er; or not 80 thick as for friimes or mould- ingS: they are to be IGcl on, by cerryin g the brush over the work in an even lund smoo:h, lxit not ilowing mitnner. l’o SUlooth theIn, or prOdUCC the ~lllGC!:S that ax requiretl, pieces Of lime-\vOo& Or fir, so&cd in watel~ . , 212 I:S!:d iliSiW:I Ol’ pumice-stone; and are shnpccl round, f!at, or n!l;;UIn:., :tS may be tixinkl necessary, occfisionallr wrapping nrountl tllcm strips of coarse linen cloth. In smootliing, care muit be taken iicJt to i;ib dr tt!o Iflad of the IVliitening, Or the gik!ing wi!l loot poor; nnil it woul,O prevent the burnishing; O[ t/rOsc prts dkh ~:‘(:re diereby brought too nc:ir to the wootl. ‘Vile (lrying m3v bchwtc:i~tl in sumwe:‘, hv thr S~UI :; or, in winter, by placing tl!e :ro;k b<~f~rc :I Grc~, bnt not too nenr; <jr tile Ivhitening \vou)(l CIII~

On Gilding in size, oil, &. 167

off. Mix a little strong size with four times as much water, in a half-pint earthen pan: the proportions should be so adapted, aS to make it three parts full: for instance, the quantity of size may,be equal in bulk, to two large walnuts, and half as much prepared yel- low ochre must bc added to it: mix the ingredients well togethei-; an& with a brus!~, co;tt the work one e over therewith: when dry, rub it sliwhtly with glass-paper, half worn out, to improve the sur- face; an(Y proceed to unis, and lay on the gold size as follows. In another half-pint earthen pan, ha”11 full of clear size, mis a quantity of burnished gold six, twice as big as a I;qe walnut, with which Coat the work twice over. \Vhcn tlr_s, burnish the parts intended to be matted, with an agate bu13i~lrf~1~; and titt’n give it another coat of the same gold six. That si7.c: ninit n01v 1x2 rcdrrcctl, by adding to it about two tea-spoonftils oi‘ ‘ivatcr, c 111tL 2s n~uch gold si7.c as yen C:ln tnkc upon the ltoilit of 2 Ltiil’~~ : Wllll ti,i. io;it ~IKW pl‘ts Ollly tllilt :LrO intcndctl to II(. i)klrnisli;~il. Alill lit:‘,! it must bc ob- servctl, thnt in layiug pltl rixc: 6111 c-ar~rci lie! I; ;~li~r if 1:; ~-cll0wcJ, those pa& should bc nii.+;rtl th;il i~rc too siil:,il to rccei\l>‘tllc gold, even from the snxtllcst pcn~i!; such as tlie hii~itij cyt>., of Ibii;q;c~, &c.; e@ct to which must aftcrwartls bc given, willi Ili,glL colourccl Oi.j7iIO/il.i4. WC may now proceed to lay (in the ~~ ~ltl u itlr il cushion-knife am1 tip, as will be describctl in oil-,, v:ltling : but in bnrliisii-gilding, Ca- mel’s-hair pencils must bc used for small parts, and swnn-quill pen- cils for the larger ones, dipped in clear water, to wet the work as fast as the gold can be laid on. The hollows and flats must be ilt first, and be perfectly dry bel’ore the other parts can be proccc cd B with : when the work is all gilt, and dry, burnish the parts intended to be so treated. Should there be any faulk. whic!l can only arise from the parts not being carefully wcttctl, 0:. ti.on~ grensc, those parts must bc rubbed through to the whitening, by means of linen wrap- ped round the finger: when they are dry, they must be gold-Geti, gilt, and burnished.

Then reduce a little clear six with hot waler; so that, rvherj cold, it will merely set: this, beinq the wcakcst size used in burnish- gi!ciing, much care should bc taken that it bc not too strong, or it will show nil the joints of the goltl. Lny On il coat Of this; and when completely dry, rub it over with cotton-rrool. In double gitd- ing, which is the best style, t!lc nmtted parts si~oulrl be agairl gilt, using water to wet as bciitrc; after which, coat IhCm again with the weak size, USC the cotlon, and, if faults appear, treat them as will be (iirectcd in ‘ d-qibfbg not to stnnd the wdlC?. After t!lc’ fallits ” are all covered, gi;e them another coat of the weak size, USC the cotton, and then give a coat of clear size, to keep tllC gOIt ftrni: a coat of or mozrlu completes the process. Observe, swan-quill ant1 catnel’s-hair pencils only arc usc4 dtcr the gold is Ixitl 011 j :Ln!i cnrc nlust bc taken, in sizing the tnnttct! prts, 110t to l~~t~\l tlllJSc iilcii are burn[shC(l, which CallnOt IX impiwd :Ift.C~r tiiC I~~ll.ll~billll~;~-Hl~iil~~.

1.

If it 1)~ rlccess:kry tf_l emb~lli5b t!lC fi.21!!t:2. or 01 h!.I. !\()I I; to I,c giI 6, nith c()lnl~(~sition ornamcntri, tllcy IlI,?v bi’ !>;!!I, iE LUli~lOIl: :,lJl’t froin tl]c press; and c;kll [JC 1;:it qi?, z!:(.I. ‘j’lc’ ‘l:~lV*ti.;L~,~s iv;‘!. ,i :‘lf:t.

168 WYNK, o)a the prcpurUtion of fiMo?te~ co~Oz&Ps, &c.

hot tllick whitening, or weak ~Iuc. \Vhsl is sqUee7ed out rOurl(i

their e(Jges, in pressing them close, may be taken off with a brusfl and cold water: they must then havea coat of thin white, to remove any grease, and be finished like the rest of the work. The compo. sition ornaments may also be put on oil-gold work, that is not to stand the weather, but does not then require the thin white: they must be finished in the manner of oil-gilding. Composition ortia_ ments are easily moistened, when dry, by wrapping them in a wet linen cloth for twenty-four hours.

[TO us COKTIRUED.]

On tile Prepnrution of Enamel Colou~, untl Flutes; cd tJLe Ve’ehicleu for luying them on with. By Mr. ROBERT LYNX.

[From the Transactions of the Society for the Encouragement of Arts, Manu- factures, and Commerce.]

PAINTIXG in enamel colours has always been considered interest- ing, and is one of tlie moat costly productions of art, in every country where practised; but the real preparation of the colours has always been confined to the knowle(lgc of a few persons, who have made a mystery of it; and whatcvcr 1~1s been yet published on the subject, ap/)eara to be chiefly the compilation ot writers unskilled in the pro- fession. hlnny artists of superior talents, in ditt’erent parts of this country, could practise the art, but for the difliculty of procuring a good set of colours: indeed it is extraordinary with what susp~ous secrecy the art of making enamel colours has hitherto been conduct- ed, 1 have been actluamted with several of the best manufacturers, whose colours were usc~l by the most eminent painters, on the tiuest and most elaborate vvorks of the time; but who have died without ever bcnefitting their country by publishing their acquirements, OI leaving any documents behiud them. It is not indeed impossible, that the present improvetl state of knowledge in the art, might bc co- tircly lost, were not snme cspcrienced professional person to seek an opportunity of makinCg it public. 02th these motives, I take the liberty to ofber the accotnpauying treatise, which consists of the most valuable selections froui t!le experience and Iubours of above twenty years.

The diRerent qualities, or degrees of purity in the ingredients, as Usually met witli, will, while following the same prescriptions, nerer- theless produce somo slight variations in their effects: but the hcst enamel colours may always be obtained with certainty, by careful attention to the following directions.

\%en metals are dissolved, their solutions shoultl always be lxx-