CEW :DIFV-3

DEPARTMENT OF COMMERCEBUREAU OF STANDABUS

V.T A O'CTTATr-yohM O*?'

LetterCircular LC 331

INKS<2T

( SupersedingCircular No. 95)

This letter circular is for the benefit of the numerous cor-respondents who ask how to make various kinds of inks. In it aregiven the formulas for the standard inks in several Federal spe-cifications, and selected formulas of inks for which there are nospeci fi cations

.

Methods of testing are omitted, because the average user ofink is perfectly satisfied if it has a good color and works well.Those who wish to test inks caqbuy copies of the specifications.See last page.

Manufacturers and others frequently misunderstand the purposeof the formulas for the standard inks in the specifications. Itis not required that inks supplied to the Government shall be madestrictly according to the formulas, but only that the inks sosupplied shall be equal to the standard inks in every essentialquality. This applies especially to the first two of the inks,because the materials used in their formulas must be of thepurity established by the United States Pharmacopoeia. Bysuitable chemical control of his manufacturing processes, anyonewho can make ink from cheaper raw materials is at liberty to doso and may sell his product to the Government, if it is as goodas the standard ink. Of necessity the materials used in thestandard inks must be of the same purity, so that both sellerand buyer will know exactly what is wanted.

Weights and Measures .

In some of the formulas the ingredients are in "parts byweight". By choosing an appropriate unit it is evident thatthe formulas can be used for making the inks in any quantitiesdesired. in most of the formulas metric units are used, and lestthe unaccustomed reader should be discouraged at the outset, afew conversion factors are given.

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LC 331 Inks 2

1 gram equals 15.43 grains, or 0.0353 oz. avoir*1 oz. avoir, equals 28.35 grams1 lb. avoir, equals 453.6 grams1 liter equals 1.0567 U.S. liquid quarts1 milliliter equals 0.0338 Iquid oz . (The milliliter

is common-fey but wrongly called cubic centimeter)1 U.S. liquid gallon equals 3.785 liters1 U.S. liquid oz. equals 29.57 milliliters1 gram per liter equals 0.1335 oz . avoir., or 58.4 grains,

per U.S. liquid gallon.

For all practical purposes, a milliliter of water weighs1 gram. By definition, this is exactly true at 4°C (39.2°F).Other liquids weigh more or less, in proportion to thoir densities.Required we ights of liquids can be converted into volumes if theirdensities are known. Thus, if the density of the liquid is 1.30,that of water being 1.00, a given weight, say 100 grams, of theliquid will have a volume of 100/1.30, or 76.9 milliliters. Thisholds for only one temperature, strictly speaking, but it isaccurate enough for the present purpose

,at other temperatures.

Ink: Copying and Record . Federal Specification TT-I-521.

All the ingredients in the standard ink must be of the qualityprescribed in the current edition of the United States Pharmaco-poeia.

Tannic acid ........ .

Gallic acid crystals . . . .

Ferrous sulphate ......Hydrochloric acid, dilute . .

Phenol (carbolic acid) . . .

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. 23.4 grams

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Here as in all other formulas, "water" means distilled water,if it can be had. Rain water is second choice.

Dilute hydrochloric acid, U.S.?., is of 10 por cent strength.Concentrated hydrochloric acid as commonly so^ld is a water solutioncontaining about 36 per cent by weight of hydrochloric acid gas, soas to make the 10 per cent acid, 100 parts hy weight of concentratedacid must be diluted with 260 parts by weight of water.

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LC 331 - Inks 3.

Soluble bluo is one of the comparatively few dyes that are notprecipitated by the other ingredients of the ink. When buying a

supply of it, be careful to say that it is to be used for makingink® See the list of dyes on a later page of this letter.

To make the ink, dissolve the tannic and gallic acids in about400 milliliters of water at a temperature of about 50°C (122°F).Dissolve the ferrous sulphate in about 200 milliliters of warmwater to which has been added the required amount of hydrochloricacid. In another 200 milliliters of warm water dissolve the dye.Mix the three solutions and add the phenol. Rinse each of thevessels in which the solutions were made with a small quantity ofwater, and use the rinsings to make the volume of ink up to 1 literat room temperature. Be sure the ink is well mixed before, it isbottled. If sealed hermetically in a glass bulb, the ink willkeep for years with practically no formation of sediment. So whenbottling the ink, have good tight corks and fill the bottles al-most to the corks.

This ink is primarily for records, and is not like mostcopying inks. However it will make one good press copy when thewriting is fresh, and this will genera 11y suffice.

Ink: Writing . Federal Specification TT-I-563.

Except for the phenol and dye, this ink is half as concentratedas the record and copying ink. It is similar to some of thecommercial writing fluids and fountain pen inks. The standard ismade in the same way as the preceding ink, and from materials ofthe same quality. If made with slightly more hydrochloric acidthan the formula calls for it will keep longer without depositingsediment, but it will bn more corrosive to steel pens.

The standard formula is

:

Tannic acid .......Gallic acid crystals ® ,

Ferrous sulphate . . . .

Hydrochloric acid, dilutePhenol (carbolic acid)Soluble blue ......

11.73.815.012.51.03.5

Water to make 1 liter at 20°C (68°F)

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L(j 331 - Inks 4.

Concentrated Ink, Powder and Table ts> Federal Specification TT-I-56I

f ic:

Concentrated ink that meets all the requirements of the speci-ition can be made by cutting down the amount of water to a

minimum, so as to make a pasty mass or a thick fluid with thesolids only partly dissolved® Instead of hydrochloric acid, whichis volatile, an equivalent quantity of sulphuric acid is used;

grams of the usual concentrated acid of 95 per centdeg. B^aumd)

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Ink powders and tablets were included when the specification*was vrritten, though all that, had been examined up to that timewere either a dye, for instance nigrosine, or wholly unsatisfactorymixtures purporting to make good iron gallo-t annate ink whendissolved in water. A few months before this letter circular waswritten, one manufacturer succeeded in making an ink powder thatmeets all the requirementsthis powder is made®

This Bureau is not able to say how

Ink: Red. Federal Specifiusation TT-I-549,

The standard ink is made byscarlet 3B in 1 liter of water.

dissolving 5.5 grams of crocein

Other Colored Inks

There are no Federal specifications for inks of other colorsthan red. Any water-soluble dye dissolved in water can be used asink, though not all dyes are equally suitable for the purpose. Itis useless to give a general formula for the amount of dye to dis-solve in a given volume of water, because of the great differencesin tinting strength. With some dyes more, and with others lessthan the 5.5 grams 'per liter specified for crocein scarlet, wouldbe required. If the quantity of dye available is small, make aconcentrated solution and dilute it by degrees until it writeswith a satisfactory depth of color. It is not safe to depend uponits appearance in the bottle. Many dyes have an antiseptic action,but solutions of others will become moldy, and it is necessary toprevent this by means of phenol or some other preservative. Onegram per liter is enough. In case the ink shows a tendency toblur or ’’feather” onof gum arable in it.

good writing paper dissolve 1 or 2 per cent

As already said, most ink powders and tablets consist of water-soluble nigrosine. A much more attractive color is naphthol blue-black, though it is not as permanent as nigrosine.

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LC 531 - Inks 5

Acid-Proof Inks .

The few samples of acid-proof inks received for test daringthe course of many years were either solutions of Prussian bluealone, or they contained in addition a dye to make their colordarker • They were labeled "blue-black", though th~t term shouldbe reserved for the iron gallo-t-annate inks that write blue, andturn black on paper*

The usual form of Prussian blue is not soluble in water, andit is technically difficult to make the variety called solublePrussian blue* Fortunately the pigment can be gotten into solu-tion by mixing it with one-fifth or less of its weight of crys-tallized oxalic acid* As some of the blup may not dissolve, itis a good idea to make the solution with less water than theformula calls for, and then to dilute it as much as seemsdesirable. From 40 to 50 grams of Prussian blue will probablybe required with 1 liter of water. Some of the few publishedformulas call for amounts of oxalic acid up to one-half the weightof the prussian blue, but we have found one- fifth to be ample.

Prussian blue ink resists attack by some acids, but alkalinesolutions decompose it and leave a rusty stain of iron oxide. Inkeradicators of the acid-Javelle water type will remove it, thoughnot easily.

Hectograph Ink .

Years before some of the modern duplicating devices had beeninvented, the hectograph was used for printing small editions ofcircular letters, etc., and it is still in rather wide use. Theoriginal is written with a special ink th t contains a large pro-portion of a dye that has good tinting strength. The letter isthen pressed face-downward upon a gelatin-glycerin or a clay-glycerin pad, which absorbs a considerable amount of the ink. Fromthis pad it is possible to print a number of increasingly palercopies upon other sheets of paper. The name, hectograph,"hundred writing", exaggerates somewhat, unless copies so pale asto be barely legible are counted. in experimenting with quite anumber of dyes, it was found that the following would give at least30 copies with unbroken lines, and numerous other copies that wereeasily legible

,though there were breaks in the strokes of the pen.

Methyl violet gave the most copies, the best red dye was rhodamineB, and emerald green and Victoria blue were the best of theircolors

.

The ink used in making these tests was prepared according tothe formula:

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LC 331 - Inks 6 .

Ac clone * ® © » © ® © © © & © ® 8Glycerin 20Acetic acid, coni® 30$ © © ® © 10vfater © . © © ® © © ® » © ® ® © oODextrin ............ 2

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All parts are by weight. If the unit chosen is 1 gram, theformula will make about 90 milliliters of ink.

Stamp-Pad Ink . Federal Specification TT-I-556.

A solution of dye in water could be used on a stamp pad, butit would soon dry out. A mixture of equal volumes of glycerinand water remains moist under all atmospheric humidities, thoughthe water content of the mixture fluctuates® In each 100 milli-liters of the mixture of glycerin and water dissolve 5 grams ofdye© The following are used for making the standards of differentcolors in the specification: water-soluble nigrosine (black),soluble blue, light green, magenta (red), and acid violet.

Recording Inks©

There is no Federal specification for recording ink. For out-door recording instruments the Weather Bureau uses inks made bydissolving about 10 grams of dye in 1 liter of a mixture of equalvolumes of glycerin and water. As this mixture will freeze insome parts of the country, it is sometimes necessary to add acertain proportion of alcohol to the ink®

For recording instruments in the labor'', torv,

the ink needsto contain only enough glycerin to prevent its drying at the tipof the pen. A mixture of 1 volume of glycerin and 3 volumes ofwater has been found satisfactory.

Almost any water-soluble dye might be used were it not thatsome of them rather unaccountably make blurred lines on the usualcard and paper charts. Dyes that have been found to work well arecrocein scarlet, fast crimson, brilliant yellow, emerald green,soluble blue, methylene blue, methyl violet, Bismarck brown, andwater-soluble nigrosine.

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LC 331 - Inks 7

Indelible Marking Ink . Federal Specification TT-I-542.

No formula for a standard marking ink is given in this speci-fication. Of the numerous formulas in books, those containing a

silver salt, and others designed to produce aniline black on andin the fibers, are most common. A typical formula of each kind is

here given.

Dissolve 5 grams of silver nitrate in its own weight of water,and add ammonia water (not household ammonia) until the precipi-tate that first forms just dissolves. Separately dissolve 5 gramsof gum arabic in 10 milliliters of warm water, and 3 grams ofanhydrous sodium carbonate (or 3.5 grams of the monohydrate) in15 milliliters of warm water. Mix the three solutions and warmuntil the mixture starts to darken. This ink should be used witha gold or a quill pen if possible, but if not, with a clean steelpen. The writing should be exposed to direct sunlight or pressedwith a hot iron to develop the color. Tho ink must be kept in thedark

.

Aniline black inks are made in one or in two solutions, theargument for the latter being that the chemical reaction thwt pro-duces the color must take place largely in the fibers where themark is wanted. There is no chance for the color to be formedin the bottle before the ink is applied to the fabric, and to makea sediment that can not penetrate into the fibers. However,excellent one-solution inks can be bought.

For a two-solution ink the following has been recommended:

Solution IlG “

Copper (cupric) chloride . . „ . 85Sodium chlorate ........ 106ammonium chloride ....... 53Water ............. 600

Solution B.-

Gum arabic ........... 67Water » ... < ... .....335Aniline hydrochloride ..... 200

Keep in separate bottles* Immediately before use nix1 volume of A and 4 volumes of B»

LC 331 - Inks 8

Drawing Inks .

There is at present no Federal specification for drawing ink*The Conner cial black drawing inks are suspensions of carbon in a

water solution that contains substances which keep the particlesof carbon from settling to the bottom; and which usually make themarks on paper or tracing cloth waterproof when they once becomedry. Shellac dissolved in a dilute solution of borax, or of boraxand ammonia, is believed to be the usual waterproofing agent, andit also acts as a ’’protective colloid” to keep the carbon insuspension. Success in making carbon inks seems to depend partlyupon long-continued grinding in a ball-mill.

Comparatively few colored drawing inks are made with pigments,but are clear solutions of dyes. Most of then are called water-proof, but all that we have examined "bled” p/Little when linesdrawn with them were kept under slight pressure in contact witha piece of wet paper. This is a very severe test. As it is notpracticable to make waterproof colored inks in the home, theprocess need not be described.

Sympathetic or Invisible Inks ,

It would be absurd to write a specification for ink that isintended for secret messages or records. The greatest variety ofsubstances can be used for ink of this kind, and some of them havebeen known and used for many centuries. The following materials,found in every home, are potential sympathetic inks: alum, soda(baking and washing)

,borax, flour boiled with plenty of water,

corn sirup thinned with water, soap, diluted mucilage, milk, lemonjuice, and saliva. Some of these are very poor, indeed, butcould be used if nothing better were at hand, .dun is by far thebest, being about as good as a drop of sulphuric acid, for in-stance from a storage battery, mixed with ten or a dozen drops ofwater. Dilute sulphuric acid has been used for many years. Thewriting in all these cases is developed by pressing with a hotiron, or holding it above a gas flame so that the paper begins toturn brown.

Many invisible inks are developed by chemical treatment, pre-ferably by fuming, but by the application of solutions whennecessary. Thus, the vapors of ammonium sulphide will formbrown or black sulphides of the metals, when the inks containany of the following: iron (ferric) sulphate, mercuric chloride(corrosive sublimate), copper sulphate, cobalt chloride, nickelchloride and lead acetate. Some of these salts are colored, butthe solutions can be so dilute as to bo invisible on paper. Cobalt

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LC 331 - Inks 9

chloride becomes deep blue in dry air or when her ted moderately,and with strong heating the writing becomes permanently black.Ferric sulphate turns black with tannic acid, and blue withpotassium ferr ocyanide. The vapor from solid iodine turnsstarch ink blue. It will even bring out faintly writing donewith distilled water on some kinds of paper, because the sizingis disturbed by the water, and this allows the paper to absorbmore of the iodine vapor '.There it was wetted.

Special Inks.

Some of the books listed on a l~ter page give formulas formaking inks for writing on metals and other special surfaces.Most of the formulas have not been tried by us, ~nd the inks arc notused to any great extent, so it seems unnecessary to devote anyspace to them.

Pigment Inks.

Once a formula has been worked out for an ink that is composedof a mixture of liquids, or of solids dissolved in liquids, it iseasy to duplicate the ink at any time; assuming of course thatthe ingredients are of the same purity as required by the formula.The situation is different if the ink consists of one or morepigments mixed with a fluid. In that case a formula simply givesan idea of how to make the ink, because the physical propertiesof the mixture depend largely upon how the materials are put to-gether. The successful producer of pigment inks must have skillbased upon experience. Besides black drawing ink and some 'withcolored pigments, there are various kinds of printing inks,canceling, duplicating or mimeograph, and other kinds in this class.

Dyes for Ink Making .

There are many more names of dyes than there are kinds, be-cause manufacturers like to have special names for their products.This readily leads to confusion in speaking or writing about dyes.To give an example: Bismarck brown, Manchester brown, phenylenebrown, vesuvine, aniline brown, leather brown, cinnamon brown,canelle

, English brown, golden brown, brown Y, and brown extraare names for the same dye, and this is not the worst case thatcould have been selected. To do away 'with this sort of confusion,two important compilations of dye names have been made. These areSchultz’s Farbstof ftabellen (dyestuff tables), and the ColourIndex. In each of these books are brought together all the commer-cial names by which each dye. type is known. Bismarck brown and

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LC 331 - Inks 10

the other dyes just named have the same chemical composition andstructure, and are therefore of' the same type. In the books, eachdye type is given a serial number, which therefore serves as a

sort of specification for the type. Instead of saying Bismarckbrown

,the buyer could get it by asking for Colour Index No. 332

or Schultz No. 284.

Those who like variety can make writing and other inks ofnumerous colors and shades by using the dyes in the list. Theyare grouped according to Color, in the same order as/the spectrum,followed by brown and black. 111

Col . Ind. Schultz

Crocoin scarlet MOO 252 227Magenta (fuchsin) 677 512Rhodaminc B 749 573

Fast crimson 31 42Diamine scarlet B 382 319Orange II 151 145

Orange TA 374 311Croccin orange 26 37Met.anil yellow 138 134

Phosphine 793 606.mramine 655 493Brilliant yellow 364 303

Emerald green 662 499Light green SF 670 505Guinea green B 666 502

Malachite green 657 49 5

Methylene blue 922 659Victoria blue B 729 559

Soluble blue (see notebelow) 707 539

Naphthol blue-black S 246 217Benzo bl ue 2B 406 337

Diamine sky blue FF 518 424Benzo sky blue 520 426Indigo carmine 1180 877

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Col.Ind

.

Schultz

Methyl violet B 680 515Crystal violet 681 516Acid violet 698 530

Alkali violet 700 532Benzamine brown 3G0 596 476Bismarck brown R 332 284

Durol black B 307 265Nigrosine, water-soluble 865 700

Note: A special effort may have to be made to obtain soluble bluethat can be used in iron gallo-tnnnat e ink without forming aninsoluble precipitate with the iron or the tannic cand gallic acids.Unless the blue is made "for ink” ,

it may not be usable. One canalways return to indigo carmine (sodium salt of sulphonatedindigo)), which was used before the days of synthetic dyes. Otherdyes worth trying because they do not form precipitates, arenaphthol blue-black S, benzo direct blue 2B

,benzo sky blue,

and diamine sky blue FI. They are not as bright in color assoluble blue

,and they should not be adopted as substitutes for it

without rigorous testing over a period of several months, incomparison with soluble blue that is known to be satisfactory.

In general it is advisable to buy dyes directly from themanufacturer, and to specify the concentrated form in each case.Many dyes are mixed with inert diluents before being put on themarket. This is a recognized trade practice, and is not to beregarded as adulteration.

Bibliography .

There is probably no public library that does not have severalof the books in the list below. Some of the books give formulasand little else, while others are concerned chiefly with thetechnical and scientific side of inks. Of the books listed,Nos. 1, 3, 5, 9 and 10 have appeared in more than one edition.

1. Brannt-Uahl, Techno-Chemical Receipt Book.H. C. Baird Company, New York, 1919.

2. Carvalho, Forty Centuries of Ink. Banks LawPublishing Company, New York, 1904.

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LC 331 - Inks 12

3. Henley, Twentieth Century Book of Recipes, Formulas andProcesses. Norman W. Henley Publishing Company, NewYork, 1928.

4. Lchner,Manufacture of Inks. Scott, Greenwood &

Company, London, 1902.

5. Mitchell & Hepworth, Inks, Their Composition andManufacture. Chas. Griffin & Company, London, 1924.

6. Rupert, Examination of Writing Inks, in Industrial &Engineering Chemistry, Vol. 15, p. 489; 1923.

7. Osborn, Questioned Documents. Lawyers’ Co-operativePublishing Company, Rochester, N. Y, 1910.

8. Oyster, Spatula Ink Formulary. Spatula EublishingCompany, Boston, 1912.

9. Scientific m^rican Cyclopedia of Formulas. Munn &Company, Inc., New York, 1921.

10. Spon, Workshop Receipts. E. & F. Spon, London, 1917.

11. Underwood & Sullivan, Chemistry and Technology of PrintingInks. D. Van Nostrand Company, New York, 1915.

12.

Wiborg,Printing Ink. Harper & Bros., New York, 1926.

Circular No. 95 of this Bureau is on Inks, Typewriter Ribbonsand Carbon Paper. It is now out of print, but can be consulted in»any libraries. It summarizes the several Federal specificationsso that these need not be bought. However, if anybody desires tohave them, they can be bought for 5 cents apiece from the Super-intendent of Documents, Washington, D. C. Sta- >s- will not beaccepted in payment. The specifications are no longer issued asCirculars of the Bureau of Standards, and are now designated asfollows

:

TT-I-521,

TT-I-542,

TT-I-549,

TT-I-556,

TT-I-563

,

Ink; Copying and RecordInk; Marking, Indelible (for) FabricsInk; RedInk; St amp -PadInk; Writing

The journal, Chemical Abstracts, gives abstracts of articles onchemistry and related subjects that are published all over theworld. It also cites patents issued in this and other countries.In the two decennial indexes, 1907 to 1916, .and 1917 to 1926, andin the annual indexes since the last date, there are numerous en-tries relating to inks.