A technical dictionary of printmaking, André Béguin.

I. DEFINITION AND BRIEF HISTORICAL OUTLINE
Ink is a substance that comes in several forms: liquid, pasty, or solid (if it is solid it can be dissolved). It is used to write with, to draw with, to paint with, or to print with.
The English word "ink" is derived from the late latin word encautum which was the name given to a red ink emperors used to sign decrees with. The latin word, in turn, was derived from the Greek word enkaunton, which was the name of the preparation used for encaustic painting. In Greek the accent fell on the first vowel of the word, thus explaining the rise of the word ink in English as well as the word encre in French. It should be remembered that encaustic painting is a very ancient technique and also that the colour red has been very important since prehistoric times because it symbolizes blood, fertility, and life. The colour red is also at the root of the word mimature (from minium).
The first inks were made using lamp black as well as vegetable and mineral colours. One of the most ancient inks is so-called India ink (also called China ink) which came from that country and was probably known before the birth of Christ. This ink was made, and is still made, by mixing lamp black or carbonized pine wood with gum or gelatine and camphor. Good quality India ink does not alter with time.
India ink began to be known in Europe as of the Middle Ages and was probably similar to a product made at the time of Vitruvius. In fact Vitruvius speaks of a machine used to collect lamp black produced by the combustion of resin and speaks of this blank pigment as being used by painters who mixed it with glue. In any case, the use of India ink became widespread as of the l8th century at which time it was directly imported from India. In fact, an enourmous amount of imitations were made of both this ink and the decorative dragons it was ornamented with.
Another kind of ink, bistre, was also well known as of the Middle Ages. Made of soot mixed with water and gum, bistre began to be used as of the 14th century. Oak gall ink was also much used. This type of ink was obtained by making a decoction of oak gall and mixing it with iron sulphate and gum arabic.
Gall ink impregnated the paper itself and, in the course of time, discoloured on the surface. Sepia, a brown pigment prepared with the fluid secreted by cuttle-fish, was not used until the 19th century. Other types of ink that may be mentioned in this historical overview are sanguine, made with red or brown earth (containing iron oxide), cinnabar, and Indian indigo.
The very first inks used for printing were much like the inks used for writing and drawing since they were water base inks to which one added a thickener and coagulants such as cooked starch. The introduction of oil and other oily substances such as butter began in the middle of the 15th century at the same time as the first printing presses. At this time painting had already begun to use oil base and resin base paints rather than egg base colours thanks to the work of the Van Eyck brothers. At first linseed oil and wallnut oil were used because they gave a new brilliance to colours. However, the transition to oil base inks and paints did not come about a11 at once, especially since there remained the unsolved problem of drying agents (in fact some of the oil paintings of this early period are still not quite dry!).
Hence even in the 19th century popular print makers still printed with a frotton and an ink made up of lamp black and a special glue.
Each printer made his own ink. In these big workshops the "ink makers" guarded their secrets jealously and thus many recipes have been lost for ever, especially since these recipes were never commited to paper but were handed down orally to the apprentices. However, all of the recipes had certain things in common. The blacks were made with left-overs of an incomplete combustion of wood and bone to which were added oil or grease. The soot used in making these inks was collected by shaking the "chimneys" made of lamb skins after burning the appropriate materials. "The best black, used to print intaglio plates, is german black which comes from Frankfurt. Its beauty and quality are due to the even texture of its velvety black colour. If one rubs this black between one's fingers one will find that it breaks up like fine chalk or raw starch. Imitations cannot produce such beautiful blacks and, instead of being soft when rubbed, they feel rough and grainy. Imitations of German black will also wear the plate down. They are usually made by burning wine lees. A very good quality black is made in Paris" (Bosse). However, black was not the only colour used as several coloured inks were available, especially red which was made with cinnabar (mercuric sulphide).
In order to bind the pigments linseed oil or wallnut oil were used but these oils but these oils had to be thickened to various degrees by cooking for various amounts of time. The resulting oil was then burned to purify it of the greasy particles [oil]. The lightest grade nil was cooked for only half an hour . The more!oil is cooked the thicker it becomes. A thoroughly cooked oil, after cooling, is "extremely gluey and stringy, much like a very concentrated syrup. Some experts put an onion or some bread crust into the oil, when it is cooking, in order to degrease it." (Bosse)
Oil that has been cooked becomes a varnish. In the larger workshops of the past varnish was made by specialized workers known in France as "cuiseurs". The varnish was then left to stand for several weeks after which the suspended mucilagenous elements were removed. At this point all that needed to be done was to add the ground up colours. At first the pigment was mixed with very little oil so as to be as dry as possible. The resulting paste could thus be adapted to various uses. The ink paste was then worked (in small quantities at a time) quite thoroughly and placed in a glazed earthenware container which was sealed tight. When the ink was needed it was removed from the earthenware container and worked again in function of the use it was going to be put to. When printing was to begin the ink was put into a container where the printer could dip the balls or dabbers he was using to ink the plate or block.
Up until 1818 this was the way ink was made. In that year, however, Pierre Lorilleux, then printer at the Imprimerie Royale, began to industrialize the making of ink. The first industrial plant for making ink was located in Paris.
Up until the end of the 18th century the range of inks had been guite limited. It was the invention of lithography by Senefelder which occasioned the diversification of inks. In fact, the inventor of lithography introduced new ingredients such as soap, tallow, wax, gum mastic, and gum, all of which were used for technical reasons. Furthermore, the components of drawing ink began to play a chemical role. Lithographic ink, which was only black because of traditional reasons, was used to draw on the lithographic stone. Lithographic ink for printing (not the same kind of ink), on the other hand, had to be particularly dense so as to repel water. Due to lithography yet another kind of ink was invented which could be used to make tranfers of an image from paper onto stone.
Mechanical printing began in 1814 and in the course of time had to be adapted to a variety of new needs: printing newspapers, printing on wrapping paper, printing on a variety of materials used for packaging foodstuffs, etc. At the beginning of the 20th century new printing techniques were invented such as offset, phototype, photogravure, and, as of the 1950's, serigraphy. This massive technological change in printing techniques also brought about the development of increasingly diversified inks. These new inks were created in response to the different criteria set up by the new techniques, criteria such as increased drying speed, the need for non-toxic inks, resistance to light and washing, the need for brilliant colours that can be seen from a distance, printing on flexible materials, and so on. The development of posters, the use of plastic, the invention of decals and stickers, etc. have been responsible for yet more research and the development of new inks.

II. THE COMPONENTS OF INK

(pigments , vehicles , solvents , drying agents , and additives)
Whatever use an ink is put to it is always made up of certain components. The two main components are the colouring matter, which leaves a visible mark, and the vehicle, which permits the pigment to be tranferred onto a surface. The colouring matter may be either a pigment or a colour. Pigments are solid substances ground to a powdery consistency which are usually insoluble. In the past pigments were made from mineral and animal substances but at present they are chemically synthesized. Colour, on the other hand, is soluble in water, alcohol, or other fluids and can be considered a kind of tint. Colours are often derived from vegetable substances.
A vehicle is the substance mixed with colours or pigments which are hard to work with alone. Most vehicles are made up of several components, each component serving a particular purpose. Thus binders are used to link and homogenize the particles of pigment. Various types of binders exist such as gum and water mixtures, emulsions, oil, and any other substance having a certain consistency and which can give some body to the ink without weighing it down. When combined with a binder the pigment becomes smoother and can be ground or mixed into a paste. This pasty stage can be achieved with varying degrees of ease depending on the materials used and, in fact, one speaks of the "wetability" of a substance to indicate the amount of binder it can absorb.
The resulting paste can be lightened, spread, or softened by adding a diluting agent. Diluting agents (which are often confused with binders) can be as simple as water. Other common diluting agents are cellulose base liquids and oils. The role of the diluting agent is to forestall an excessive viscosity and, at least in theory, to evaporate during the drying process and disappear entirely. The diluting agent must not be confused with the solvent whose task it is to dissolve a dry subtance. However, a solvent can be used both as a diluting agent and to dissolve, as is the case when white spirit is used on nil base inks. On the other hand, the two functions may also be separate. Thus a water base ink is diluted with an emulsion of oil and water but it is dissolved with acetone. Whereas a diluting agent is usually specific, a variety of solvents can generally be used. In practice, however, the diluting agent is often called a solvent.
The major problem encountered by a printer once he has finished printing his work is the drying process. In order to activate the natural oxydation of oily inks, ink makers usually add drying agents when grinding their pigments and when mixing their paste. It is also possible (in certain cases only) to intervene when printing by adding accellerators or retarders which expedite or slow up the drying process but which are often detrimental to a maximum keying of the ink.
Finally, a certain amount of secondary substances can be added before or after grinding the pigments. These substances affect the transparency of the ink, its thickness, or its softness.

III DESCRIPTION OF VARIOUS TYPES OF INK

1. DRAWING INK. A. INDIA INK . India ink (also known as China ink) is the archetypal drawer's ink. It may be had in solid form, in which case it comes in the shape of a flat square, a stick, or a variety of other shapes which are often decorated with oriental characters. An ornamental presentation, however, gives no proof of quality or authenticity. India ink also comes in liquid form in tubes or little bottles. This kind of ink is made from lamp black (also called carbon black) or carbonized pine wood to which are added gum or gelatine, Borneo camphor, and powdered musc. Imitation India ink has long been made using burnt colophony, candles, paper, and even fruit stones. The best quality India ink comes in solid form and smells of Karpura resin (which comes from a ]apanese tree). In any case, the solid block must by no means have a lacquered finish since this finish is applied only to unstable products which must be protected from alteration.
India ink is perfectly black and, in theory, is perfectly stable after drying. However, this is only true if it is of good quality and if it is perfectly pure. In the far East the preparation of this ink is nothing short of a rite and ink is considered to be one of the "four treasures" of a scholar's study along with a grinding stone, paper, and brushes.
In order to obtain a pure India ink from a solid block one must rub the smallest side of the block on the surface of a special stone. The Chinese and Japanese stones made for this purpose are just barely mat finished and have a little hollow where the water is kept for diluting. One can also use mat finished glass or a rough surface on which the solid ink will stick. Some artists prepare their pure ink in a saucer. Some water is put in the bottom of the saucer and the stick of India ink is rubbed rapidly on the edge of the saucer which is inclined to facilitate the job. The ink powder must fall into the residual water at the top of the saucer and not directly into the puddle at the bottom. Ink prepared this way is for immediate use and is usually used to apply layers of deep black and for brush work. Sticks of ink must never be left to soak in water as otherwise they will crack and crumble into pieces.
India ink may also be had in liquid form. In the past there was a great difference of quality between the liquid and solid varieties and because of this liquid ink was only used for line work whereas tone work used a solution of solid ink. The liquid India ink produced by reputable manufacturers is, at present, perfectly reliable for any kind of work. However, it must be pointed out that manufactured liquid inks are less fluid than those made with a solid ink and because of this they tend to clog the instruments used for line work. It is thus necessary to clean the instruments more often. Furthermore, manufactured liquid inks are hard to dilute since the colours tend to settle. In other words, the solid particles in the ink do not mix well with the diluting agent and because of this the particles collect on the bottom of the container leaving a layer of pale water at the top. On the other hand, liquid India ink has the advantage of being indelible and therefore it can be used for superimpositions. India ink made with solid ink, however, tends to wash out when superimpositions are practiced.
When India ink is used for line drawing it is usually used to cover a preliminary line drawn with a pencil.
Left-over India ink must not be used since old ink becomes scaly and sticky.
< The following recipe is a substitute for India ink which is indelible and can thus be used for superimpositions. The ink does not form deposits and does not attack instruments made of steel.

aniline black			4 g
alcohol			15 g
gum arabic			6 g
water			90 g
hydrochloric acid			60 drops

In printmakingf, India ink is used to draw on wood blocks as the lines are not easily ruined by handling while work is being carried out on the wood and even even the rubbing of a hand will not affect the drawing. The illustrators of the 19th century often used India ink on their blocks which were then engraved by professional engravers. This kind of ink is also used in pure or diluted form for Japanese printing techniques [wood].
India ink can, be used in the sugar lift process. In this process the ink is saturated with sugar and is then used with either a pen or brush to draw on a perfectly clean plate. After drawing, the plate is covered with a thin layer of varnish and is plunged into water (rain water is best). This causes the sugar to swell and crack or "lift" in the areas where the ink drawing was made. The next step is to etch the plate as with any other type of etching. If any large uniform areas are exposed using the sugar lift process they can be grained if so wished [graining].
In serigraphy India ink is used for photographic work using transparent films (typons). This kind of India ink is, however, specially made to stick to plastic sheets by dissolving them superficially.

B. ORDINARY INKS. Even though this class of inks is very rarely used it must be at least mentioned briefly. Ordinary ink is used in the ink-lift-process perfected by Bracquemond. This ink lift process is much like the sugar lift process mentioned above. The main difference is that ordinary ink is lighter and thus allows for finer lines.

C. CHEMICAL INKS. Since the times of Senefelder chemical ink has been used to write or draw on stone, zinc, or aluminium (three lithographic technique surfaces). This kind of ink must not be confused with the ink used to print lithographies. "Chemical ink, which one may also call greasy or alcaline ink, derives its name from the fact that it contains a mixture of greasy, resinous and alcaline parts. It is one of the most important an necessary materials for a lithographer" ( Senefelder, The Art of Lithography). The essential components of chemical ink are tallow, wax, and resin. The reader should remember that the only reason black pigment is added to this ink is to permit the person making the drawing to see his work as it progresses. Pigment serves no other purpose in this ink. The greasy substances mentioned above are not soluble in water and, in order to make them easier to work with, some soap must be added to them. When the drawing on the stone has been completed it is then washed with an acidulous preparation which neutralizes the alcaline substances and makes the greasy elements become insoluble again. The tallow used for chemical ink is often sheep tallow since it contains very little oil. The grease content of the ink is what makes it solid but if the content is excessive the ink becomes too soft. Wax, on the other hand, gives consistency to the ink and prevents the tallow from spreading. However, if too much wax is used the ink will dry too fast and become brittle. In such a case the ink must be continually thinned with water or oil. Resin gives fluidity to the ink (after being saponified) but if it is used in excess it will dry the ink and makes it insoluble when cold.
Chemical ink must be strong, in other words even a large amount of impressions must not affect the lines. Such ink must be resistant in order to protect the stone from the acids. An excessive use of soap will reinforce the ink but will also make it become quite gluey.
In order to make chemical ink, melt wax and tallow in a cast iron pot which must not be more than one-third full. When the mixture reaches about 200°C (about 400°F) add soap flakes and stir briskly. The mixture must be hot enough that it will catch fire when touched with a burning match. While the mixture is burning mix in the resin (shellac). Then smother the fire by covering the pot with a lid and then proceed to add the black pigment. The mixture should then become quite pasty and can be put into boxes and covered with tin foil.
The ink thus prepared can be dissolved in either distilled water or oil, depending on the ingredients used. In order to obtain a liquid ink mix it (when still pasty) with some boiling hot distilled water. Solid ink can be diluted in much the same way as India ink using a liquid and a bowl. Chemical ink may be applied with either a brush or a pen.
Since the times of Senefelder a variety of recipes for chemical ink have been invented. Thirteen well known recipes are given below. The table containing these recipes was sent by the Lorilleux Company of Bruxelles to the Belgian Ministry of Economic Affairs in 1920 when the Ministry undertook to publish a monograph on lithography. The amounts are all in grams (1 gram= 0.035 ounces avoirdupois or 15.4 grains).

ingredients			1	2	3	4	5	6	7	8	9	10	11	12	13
white wax			100	100	100	100		100	100	100	100		100	100	100
yellow wax												100
yellow soap, Marseille soap			30	54	325	100	20	45	50	25	160	250	100	50	100
lac			200	70	150	100	100			25	140	25	125	125	75
gum mastic in drops			10	25			20		25				25	50
purified tallow			20		75	100		34	25		160	75	75	75	100
lamp black			5	22	75	7	7	13	25	25	50	50	25	25	25
soda						20
Venice turpentine									13				13	21
olive oil														12

Recipe n.3 is Lemercier's, n.10 is a German recipe for brush work, n.11 is the Doyen recipe, n.12 is the Knecht-Senefelder recipe, and n.13 is the Chevalier and Langlumé recipe.
Lithographic crayons are made with much the same ingredients as chemical ink but they are not water soluble.
Chemical ink can also be used in serigraphy and in manual screen processes, as a kind of ground in etching and in a zincographic* process which creates relief blocks using electrolysis [galvanography, electrotyping]

D. AUTOGRAPHIC INKS.
Autographic ink is much like the chemical inks used for litho drawings. In fact, chemical ink can also serve in autolithographic* work. Autographic ink is used for writing or drawing on autographic paper instead of on the stone itself. The work done on paper is then transferred onto the stone by passing both the stone and the paper through a press (the paper resting on the stone must be wet). The following recipe can be used to make autographic ink. Mix the ingredients in the following proportions:

white. wax			100 parts
yellow soap (Marseille soap)			80 parts
lac			160 parts
dragon's blood			60 parts
purified tallow			50 parts

At times a bit of sulphur is added to increase the fluidity of the ink. Sulphur also preserves the mixture for several years without any problems. If this ink is too light in colour add some India ink to make it darker.

E. LATEX (rubber) INKS.
Actually this category of inks are all rubber base inks used in serigraphy for positive screen preparations, in other words the lines made with this type of ink will be printed through onto the impression. Add water to the commercially made inks until the proper fluidity has been reached. This kind of ink can be applied either with a brush or with a pen. If it is properly made it will make a relatively precise line and even very thin lines can be drawn by working rapidly. The instruments must be rubbed with a bit of soap before putting them in the ink so that the ink will flow better. Remember to wipe the instruments often and to clean the edge of the ink-well. The removal of this ink is easy. Wait until the line has dried completely, at which point rub it away with a finger. If another line is to be drawn in the same place it might be necessary to remove the previous line with acetone. Be sure to clean the area perfectly otherwise the new line may be a broken one.
When the completed image on the screen is dry it must be covered with a layer of filler. This step is quite a delicate one and must be carried out very quickly. When the filler has dried proceed to remove the dried latex ink with your finger or with a soft eraser. Dissolve the remaining ink residue with turpentine oil. As a result the areas covered with rubber ink will now be open since the filler does not penetrate latex ink. The ink used for printing will then go through the lines of the drawing and onto the silkscreen print.
Latex ink can be used with good results in etching since it can be used to draw on plates. When the drawing is completed and the ink is dry proceed to spread a liquid ground with a brush. When the ground is also dry carefully remove the latex ink drawing with your fingertips. The etching will be a positive one since biting will only affect the drawn areas.

2. TRANSFER INKS.
This particular type of ink deserves a separate description because it must not be confused with printing ink. In fact, transfer ink is used to ink drawings that have already been done on lithographic stones and which need to be transferred onto another stone because the first is either broken or needs to be kept as nn original, or else because several stones are needed for greater speed and for economic reasons. At times even line and relief engravings can be tranferred.
The first step in making lithographic transfers is to make an impression on autographic paper or on transfer paper using transfer ink. The ink of this impression will be transferred onto another stone. Hand printed impressions are never very satisfactory and must be repeated. The following is a general recipe for making transfer ink:

yellow wax				300 g
sheep tallow				30 g
white soap				120 g
colophony				240 g
weak varnish				370 g
lamp black				enough to colour the mixture

3. PRINTER'S INK.
A. WATER BASE INKS.
These inks are used to print Japanese woodcuts, hand stencils, monotypes, and silkscreens. Although the ink used for each one of these techniques is made somewhat differently they all have a mat finish when they are dry [paints]. The inks used for Japanese woodouts have light colours similar to water colours. The colours are dissolved in water to which rice glue or gum arabic has been added. The ink is applied rapidly with a large brush in the direction of the wood grain. India ink is also used to print such woodcuts but it is used in diluted form. Darker tones are obtained by either superimposing several colours or by adding some black.
In the case of hand stencils the ink has almost the colour of gouache. It is pasty and opaque due to the fact that the colours are mixed with gum arabic and some white. In the past artists even used to add some honey to this ink. The colour is applied to the stencil covered surface with a pochon (a stiff brush whose bristles are cut to the same length all over). The brush must hit the stencil in a succession of little vertical blows.
Insofar as the monotypes are concerned water base inks or paints are sometimes used if they have a certain amount of consistency and do not dry too quickly. However, as these characteristics are not typical of water base inks and paints, monotypes are usually done with oil base colours.
The inks used in serigraphy are specially prepared to fulfill three necessary conditions:

• the inks must be soluble after use so that the silkscreen can be recycled (can be used again).
• the inks must not dry too quickly in order not to clog the screen.
• the inks must be thick enough to permit a precise impression.

Too liquid an ink does not respect the stencil effect of the screen and spreads on the impression to form imprecise spots.
Specialized suppliers carry specially prepared inks. These inks are usually made by diluting colours in an emulsion and then adding a fixative (usually gum). The ink comes in pots or in tubes and must be mixed, just before use, with a vehicle (generally an oil and water emulsion). One must not add pure water to these inks.
Water base inks are only used to print lines and line work because if they are used to print larger areas they tend to wrinkle the paper, especially if superimpositions are practiced.

B. OIL BASE INKS.
This type of ink is the most commonly used (and has been since the 15th century) for typographical work, for printing intaglio or relief engravings, and for lithography. These inks have a shiny aspect before use and after drying they are more or less glossy, satiny, or mat depending on the type of ink used and the type of paper printed on. Oil base inks can also be used to print monotypes but artists usually prefer to use oil base paints.(???)
Oil base inks are made using a pigment paste mixed with water (i.e. a pigment ground in water) or then a dried pigment in powder form. The next step is to add a certain amount of oil and some other substances to act as binders between the particles of pigment. These ingredients are put into mixers which disperse the pigment evenly in the varnish. Once this has been done the resulting paste is ground up. Grinding is a delicate task and, in the past, it was done by hand but today it is done mechanically with a machine whose cylinders compress the paste several times over. When the paste is sufficiently homogenous it is poured into containers where it is left to settle for several weeks. This paste becomes the base for making inks and it is subsequently reworked in function of its colour, consistency, and dryinq characteristics. All of these steps are closely controlled so as to ensure the quality of the inks thus manufactured and sold.
The vehicle of an oil base is called a varnish. Varnish is made, above all, with oil but other ingredients are also employed such as resins, fatty substances, waxes, soaps, etc. The oils used for this purpose are always cooked oils of the type that thicken when cooked, as is the case with linseed oil which is the most commonly used one. The more oils are cooked, the thicker they become because heat rids them or their fatty acids. In order to avoid the production of acidity during the cookihg process, however, it is necessary to add some glycerine to the oil. In the past the degreassing was done by burning the oil. At present the burning is usually replaced by cooking which is done in a special double-chambered apparatus.
Three to six different grades of varnish can be obtained by cooking, the most fluid being those that have been only slightly cooked. The fluid grades of varnish are extra-weak, weak and medium. The thickest grade is very pasty and is only used to give some body to the ink being made. Varnishes are also used in artists' workshops to thin inks before use. For manual impressions only three varnishes are used: clear or white oil (which gives the most fluidity to ink), fatty oil (which lightens ink but permits it to retain its consistency) and heavy oil (which, being the thickest of the three, is used sparingly to give the right viscosity to the ink). Very little heavy oil should be used since it complicates wiping the plate before printing. Black pitch and colophony must be added to heavy oil after it has been heated to 300°C (572°F).
The consistency of greasy inks is in function of the use they are destined for. For relief printing they must be creamy with a certain amount of body. The inking of wood blocks is done with vignette black which contains some resins. For intaglio work there is a variety of inks but all of them must be heated before use (25 to 35°C - 77 to 95°F). Intaglio ink must be thick enough to stay in the hollows of the plate but not so sticky as to complicate the wiping of the plate before printing. Furthermore these inks must not be water sensitive since the paper used to print intaglio plates is often dampened. There are also different kinds of inks used to print etchings. Some are more easily wiped, others stick better. The printer must choose the one that best suits his purpose.
If an intaglio printer wishes to make his own ink he can make a basic mixture by grinding the pigment and mixing it with a varnish made of raw linseed oil (100cm³) and heavy oil (50cm³). The varnish must be heated in a double boiler and then left to cool off. The powdered colour is then piled up in the form of a mound and the varnish is gently and gradually poured onto the powder. Add the varnish a little at a time and work the mixture with a palette knife until a thick and glossy paste is made. A thinker paste can be made by diminishing the amount of raw linseed oil and by increasing the amount of thick oil.
The inks used for embossing are very quick drying and have a glossy finish to them. The inks used for printing lithographies are quite thick ones and the pigments are selected so as to be insoluble in the water used to dampen the paper. In fact, a certain amount of fatty materials are added to lithographic inks to increase their water repulsion. The colours used for offset* are very strong ones as they must compensate for the losses that come about during the transfer process that characterises this technique. The inks used in phototyping must be both dense and insensitive to water.

C . SYNTHETIC INKS. These inks are generally used in serigraphy and date from when this technique was first invented. At present silkscreening is quite often done with highly resistant mat finish ink. These inks have a very mat finishand, when printed, have a fairly conspicous relief (layer of ink). Furthermore, these inks are very opaque and do not suffer from exposure to light. On the other hand, they are fragile and breakable when manipulated. These inks can be made to shine if they are rubbed.
Synthetic inks are diluted with white spirit or then with a specific solvent. It is essential not to let these inks dry on the screen as otherwise it will be impossible to use the same screen again.

D. CELLULOSE AND ETHYLCELLULOSE BASE INKS. These inks are also used in serigraphy and have various types of finish: mat, satiny, and glossy. These inks seem to be replacing synthetic inks since they are more resistant and dry less easily on the screen. When printed they cause very little relief (the ink layer is quite low). These inks are diluted with either white spirit or a specific diluting agent. White spirit is used as a solvant for ethyl cellulose base inks whereas acetone is used for cellulose base inks.
Cellulose base inks have a very particular odour that some people find unpleasant. These inks dry quickly and can also be used on coated paper, which is not the case with synthetic inks. Cellulose inks are, however, quite hard to superimpose.

E. GLYCEROPHTALIC INKS. This category of inks is characterized by the fact that they are very glossy, opaque, strong, resistant (especially to rubbing), and are light fast. Their drying process is slow and therefore certain precautions must be taken. In particular, care must be taken that no dust settles on the printed surfaces for two or three hours after printing.
These inks are diluted with white spirit or with a specific diluting agent. However, they must not be overly diluted if they are to retain their glossy finish. The screen must be cleaned immediately after use with spirit or acetone. At times it will be found necessary to clean the screen in the course of printing.

F . SPECIALTY INKS. Under this heading come all luminescent inks (inks that reflect light in a particular way). These inks are fluorescent, phosphorescent, and metallic finish inks which contain a certain amount of metallic powder in suspension.
Fluorescent inks are mat finish inks. Serigraphy is certainly the technique that has made the most use of them. Fluorescent inks must be printed onto a white background and must be diluted as little as possible. Their light fastness is quite low since their life span is only a few weeks if exposed to full sun light. These inks are diluted and cleaned with white spirit. They are printed onto relatively absorbant surfaces. Golden, silvery, and bronze coloured inks are usually glycerophtalic inks or cellulose base inks. The powder used to make these colours is mixed into the ink just before use and tends to deposit heavily [*dusting].

4. BITING ( etching ) INKS . In concluding this description of the various inks available to the printmaker I would like to speak of a variety of inks which are neither for drawing nor for printing but which are used as a kind of etching* ground or an acid resist in gillotype , photo-engraving.
In other words, these inks are used to make relief blocks onto which the image is transferred by photographic means and then etched chemically.
The areas of the block which are to appear in relief are first covered with a soft black ink that 5 will permit a first shallow etching. The ingredients of this ink are, according to L.P.Clerc:

colophony in pieces				25 g
yellow bees' wax				200 g
black typographical book work ink				500 g

Heat the mixture and then, before it cools off, slowly add 200ml of turpentine oil, mixing thoroughly h all the while.
For the successive etchings that must be undertaken to increase the relief one should use a hard black ink which is made with the following ingredients:

Burgundy pitch				60 g
colophony in pieces				75 g
swedish black pitch				100 g
asphaltum in pieces				100 g
yellow bees' wax				100 g
black vignette ink				500 g

In typographical language book work impressions are those of a certain quantity/size as opposed to the printing of catalogues, visiting cards, etc. which can be done in the smailer workshops in the center of town. Vignette ink, which contains waxes, is a typographical ink of good quality which is particularly suited for printing ornaments, rules, tail pieces, etc.

IV. THE CHARACTERISTICS OF INKS .

1. BEFORE PRINTING.
A. THE CONSISTANCY . The inks one buys commercially in boxes or in tubes are rarely ready for use. Usually they must be diluted to make them more fluid but sometimes they only need to be made more viscous for use. Other corrections may be required such as increasing or decreasing the siccativity of an ink, its opacity, its transparency, etc.
The viscosity or compactness of ink is proportional to its resistance to being worked. The viscosity of ink is the opposite of its fluidity. Diluting agents make an ink more fluid. To make ink more tacky one may add to it a thick varnish (heaviest grade cooked linseed oil, for example) or then it may be mixed with an inert powder or sand that has been ground to a fine powder. Ink manufacturers sell specific thickeners for some varieties of ink. Water is the diluting agent used in water base inks while oil is used to dilute oily inks but all of these diluting agents must be used sparingly as they diminish the intensity and the tackyness of' ink. In fact, it is better to use emulsions for water base inks and varnish for oily inks. In serigraphy white spirit, specific diluting agents, or thinners are used to increase fluidity. However, these additions must be precisely dosed so that the ink maintains a proper consistency. Usually a maximum of 5% is added and only rarely more than this.
Insofar as the preparation of the inks is concerned one must distinguish between fluidity and dilution. Furthermore, a distinction must be made between the tackyness of an ink and its intensity even though the two are related indirectly by dilution. An ink is intense when the pigment in it has a high degree of colour strength (chroma). Hence intensity varies according to the amount of pigment used.
Generally speaking it may be said that, when an ink with a fixed intensity is fluidified its intensity is diminished. Actually there is always a maximum amount of fluidification that should not be exceeded.
This maximum is not constant as it depends on the printiog technique adopted. The maximums are mentioned in the articles concerned with the individual print making techniques.
The viscosity of ink is related with its yield value and the spreading it can undergo. These notions are particularly important when working with mechanical presses since the distribution of the ink in such presses is done automatically. However, these concepts are also important in manual printing techniques.
In tact, an ink that is applied with a roller or with dabbers must spread properly and be such that it penetrates the intaglio areas without problems. The heating of the ink increases the fluidity temporarily and because of this printers have recourse to heating in order to print intaglio plates which require relatively large amounts of ink. The right viscosity of oily ink is achieved by working it on an unpolished slab of glass with a mixture of light and heavy oil. lntaglio plate printers may use the following mixture to fluidify their ink:

cooked linseed oil (clear)				100 g
greasy oil				50 g
raw linseed oil				100 g
heavy oil				35 g

There is also such a thing as thickeners, which we already mentioned, usually already added to the ink. The viscosity of water base inks is obtained by mixing them, in a container, with a medium. The inks used in serigraphy are, on the other hand, lengthened with a specific diluting agent.
Mechanical mixers with propellers can be had (used above all to mix the colours) which ensure an almost perfectly homogenous result. However, an ink can be more or less tacky independently of its viscosity. The tackyness of ink or its pull is the resistance it exerts to lifting. Therefore tackyness is not to be confused with the viscosity.
Actually the tackyness of an ink is dependent on the viscosity of the binder used. We have seen, for example, that the varnish used in oily inks can be very tacky by itself as in the case of the heavy oils that are added in small quantities and make the ink sticky. The tackyness of inks must be calculated and brought about in function of the wiping and printing that has to be done. An ink can be wiped and printed all the more easily if the tackyness is very slight since this makes the separation of the printing element surface from the wiping surface and/or the printed surface all the easier. On the other hand, the tackyness must not be too low otherwise the ink will not stick to both the printing element and the printed surface.
One must therefore bear in mind that there are two different characteristics which determine the consistency of an ink. The viscosity of an ink permits it to spread on a given surface whereas the tackyness allows it to stick to a surface.
An ink is said to be stringy when it forms strings while being spread. The opposite consistency is similar to soft butter, in which case the ink is called buttery ink.

B. COLOUR CHARACTERISTICS. The use and functions of colour in printing work are extremely vast. The reader may turn to the article on colour for information concerning the various colour reproductive techniques. This section is concerned with the problems of defining, describing, and using colour inks.
Generally speaking, colour is tbe most important part of an ink whether the colour be yellow, red, blue, green, white, or black. Colour can also be defined in opposition to black and white i.e. as being part of the colour spectrum of sunlight. It is a well known fact that the colour black absorbs all of the light rays in the spectrum whereas the colour white repells all of the spectrum's rays.
A tone is the characteristic of a particular colour. Geranium red and crimson are both different tones of red while pea green and Veronese -green are tones of green.
A hue or shade is the softening or toning down of a particular colour or the tone of a colour. Thus it is possible to tone a colour down by using some white or (which is the same) by making a colour more transparent when applied on a white surface. The same procedure is used for tones. Shades or hues can range anywhere from the maximum intensity of a colour (or tone) all the way to a shade that can hardly be distinguished from white.
While on the subject it may be pointed out that there are two different kinds of white. Cover white (zinc white) is a real colour and can be printed on a more or less dark background and can also be used to tone down colours. The other type of white is called transparent white. Transparent white is not really a colour but it is used to soften colours. Transparent white is a kind of laque which can be added to colours in varying degrees. The colours then becomes less intense and the hues lighter but the consistency of the ink is not modified [* white].
Colour can also be made darker by adding some black. Darkening can range anywhere between the maximum intensity of a colour to its becoming indistinguishable from black. One can also darken a colour by mixing it with its complementary colour (yellow and violet, red and green, orange and blue).
Blacks can be - quite different from one nonther as they can be more or less intense depending on the pigments used. Blacks and whites are not used in their pure form expecially in printing intaglio impressions. In the 19th century it became fashionable to add some bistre, Sienna, umber or Venice red to make a warmer black.
A colour is called a simple colour when it is made with only one pigment. When made with several pigments it is called a composed colour.
If mixtures are to be made it is best to make some trial tests with samples, trying to remember the proportions of the pigments used. Dark colours should be added to light colours and not the other way around.
A colour must be judged in day light and on the same paper used for the envisaged impressions. It is a good idea to note in the margins of these samples the proportions of pigment used, the quality of the ink, the quantities of diluting agent used, and any other ingredients that might have been introduced. The main components used to make an ink should be weighed and their weight recorded.

2. DURING IMPRESSION.
A . COVERING POWER . When printing begins a whole series of new problems are posed. First of all there is an economic problem, which is relative when small runs are being dealt with but which must be taken into account by big workshops dealing in big runs. The economic probles is directly linked to the covering power of an ink. In fact, and especially in serigraphy, a surface can be covered by varying quantities of different ink. Ethyl cellulose inks have, for example, a relatively high covering power. Manufacturers often mention the covering power of their products on the package. An ink can be given a greater covering power by adding an extender or reducer but as we have already seen, such additions are often detrimental to the ink's intensity and sometimes even affect its "keying" power (see below)
Very often the term "keying power" is used to describe an ink's opacity.

B. OPACITY. When speaking of ink it is a good idea to distinguish between the two terms "covering power" and "opacity". The opacity of an ink refers to its ability to hide a background. Opacity is the opposite of transparency. These two notions are essential for the study of colours since colours can be obtained either by applying a solid colour or by superimposing two (or more) transparent colours to bring about new hues. The three colour process is based on the principle of superimposed transparent colours. As the term suggests this process uses three basic colours which are blue, yellow, and magenta red. An ink can be made more transparent by mixing it with a diluting agent or a tranparent base.
Superimpositions can cause problems when colours overlap or touch each other. Two inks should not discolour one another. It is said that an ink bleeds when it reacts with another ink. Manufacturers usually warn consumers if their inks bleed. On the other hand, some colours can only be obtained by using pigments that react with one another.
Another problem may arise when superimpositions are practiced. In fact, one layer of ink may refuse another especially if the first layer is too dry or too smooth.

C. KEYING . Keying is the term used to designate the property which causes ink to stick to a surface. Ink can stick to a surface in a variety or ways. First of all, ink can stick by penetration if certain conditions are fulfilled: the ink must be quite fluid if it is printed on an absorbant support, or, if support is not absorbent, the ink must have a certain degree of tackyness. If the keying of the ink is not right the ink may "lift" or come away. "Lifting" comes about when the printing element and the support being printed on stick together because the ink does not come off the plate easily, it has problems in being transferred. What happens is that the paper sticks to the plate or block and is ripped.
The reasons for such accidents are often due to the fact that the ink is excessively tacky or the paper is too damp.
The dilution of fluidification of ink may facilitate keying but one must not exagerate since excessive fluidity may cause yet another problem. If the paper being printed on is very absorbent the ink may show through; in other words it might go through the paper and show up on the other side.

D . SICCATIVITY . During printing procedures ink begins to dry. This phenomenon affects impressions in varying degrees depending on the technique used, hence it must be taken into account in each individual case. In serigraphy the siccativity of ink is one of the more important considerations because the ink must not dry during the printing procedure otherwise the silkscreen will be clogged. One must, therefore, have an ink that remains fluid and, if necessary, a certain amount of retarder must be added. However, the longer the ink takes to dry the more problems one encounters in drying the impression and therefore an organizational problem arises in taking care of the fresh impressions. Silkscreening thus entails a kind of contradiction which we will discuss further on in terms of its possible solutions.

3. AFTER PRINTING.

A. THE FINAL ASPECT . A printed ink always has a particular aspect or finish. This aspect may be glossy, satiny, or mat. Any objective conclusions as to the finish of an ink tan only be reached when the ink has dried on a particular support or surface. The final aspect of a glossy ink, for example, will be quite different on an absorbant variety of paper than on a coated paper. Because of these differences one should make samples to determine the end result.
It is known that coated paper tends to give a certain glossyness to ink if the ink is not to mat. Much the same thing will happen with superimpositions of ink, as glossy layers favour the application of other glossy layers. One can also increase the glossyness of an ink by adding somewhat more varnish. In fact, this is the way in which relief and lithographic impressions are given a satiny finish even though they are printed on very absorbant paper. Intaglio impressions usually have a mat finish. In serigraphy, on the other hand, the variety of inks is such that all possible finishes can be had. It is even possible to bring about a final glossy finish with mat finish inks by simply applying some overprinting varnish once the impression has been printed [ paper, varnish].

B. DRYING. The problem of drying arises when the impression is completed. This stage of printing must not be confused with the drying problems which occurr during printing and which are mentioned above. In mechanical printing the inks used are fast drying ones so that the impressions can be piled up immediately after printing. However, it is sometimes necessary to powder the impressions with a special anti-slurring powder or then slip sheet them (set one sheet off from another with sheets of clean paper) so as to avoid slurring. These procedures are also carried out to avoid one impression sticking to another, a phenomenon which comes about if the ink dries too fast and thus heats up. In manual printing (which is the most commonly used system in print making) the impressions are run off at a reduced speed and therefore they need not be piled up. Engravings and lithographies are usually covered with a sheet of tissue paper and this prevents most problems.
Insofar as drying is concerned, serigraphy is the technique that presents the greatest problems. As we have already seen, the inks used in serigraphy must be stow drying so as not to clog the screen. On the other hand, the slow-drying ink of serigraphic impressions cannot be covered when still wet, not even with a slip sheet since the inks remain sticky for quite some time (as much as several hours).
In the drying process of these inks one may distinguish between the dust-free stage (the point at which the ink is dry enough not to catch dust) and a proper drying (which is when the ink is dry enough to avoid slurring). These two stages take quite a long time in serigraphy and therefore the impressions must be dried separately (individually) on racks or hanging from a clothes line. The drying time increases in function of the ink's thickness and glossyness. Some inks, such as glycerophtalic inks, first dry superficially and then continue to dry below the exposed surface. The oxydizing process that must be complete throughout the applied ink is thus slowed up by the superficial dry crust.
The various drying procedures, especially the artificial drying or silkscreen work carried out in large workshops, are very different as they depend on the type of drying required: evaporation, penetration, or oxydation [* drying].

C . THE RESISTANCY OF INKS. One speaks of. the resistancy of an ink in terms of its ability to withstand the damage incured from rubbing, light, scratching, bending, heat, and washing.
Light proofness is mainly ensured by the right choice of pigment. Inks used in serigraphy are submitted to the greatest mechanical stress, especially if the applications are quite thick. The thickness makes ink brittle. Generally speaking, thin inks that penetrate the surface they are printed on are the least delicate in terms of mechanical stress. The problems caused by washing inks are not of much importance in printmaking.

D. STORING INKS. The storing of inks always causes problems for the printer. In fact, all inks are made in such a way that they dry and sometimes they are made so that they will dry rapidly, hence there is no reason to be surprised by the fact that that they tend to dry up in the storage container.
Generally speaking, inks are best kept in a warm place. Insofar as solid inks are concerned, one must scrape the surface rather than making a hole when taking the ink out of the can. Each printer has his own technique for protecting inks. Solid inks in cans can be protected with a disk of paraffin or wax paper. Similarly, the ink can be covered with a layer of mineral oil or water. The important thing is to protect the ink from contact with air. If this is not done a kind of skin will soon form on the surface and the more time goes by the more the skin will thicken until the can becomes quite unusable.
Ink that is kept in tubes is easier to deal with but as such ink can only be used for small quantities of work ; tubes are usually only used by amateurs.
Water base inks will not dry up if they are hermetically sealed and if the can or container is sufficiently full of ink.
Synthetic inks form a skin and dry up, a little at a time, even in a well-closed container. Ethyl cellulose and cellulose base inks do not dry up if the conininer they are kept in is hermetically sealed. Glycerophtalic inks are difficult to keep even if one covers them with a layer of white spirit.