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A technical dictionary of printmaking, André Béguin.
An etching technique practised on metal plates by means of biting with a mordant. The purpose of this technique is to end up with an impression whose values are akin to wash drawings, dot work, or ruled work as opposed to the values obtained in line work. Aquatint may be distinguished from all engraving done directly with tools (used for both line work and dotted work) such as gravers, needles, roulettes, poles, etc. Aquatint may also be distinguished from line etching even though it is classified under the general heading of etching. At times it is considered to belong to the processes called lavis or wash manner which were, in fact, at the origin of aquatint. However, one should not assimilate the lavis manner and aquatint since the latter can be distinguished by its qranulated surface*. The term granulated is here used to describe a plate surface pock-marked by many small and closely spaced holes whose function it is to retain ink and, when impressions are made, print black. The result (impression) made by such a plate surface is the grain. The graining of a plate is an extremely delicate operation which gives aquatint its characteristics and subtle values.
Although the first imitations of wash drawings in print making can be traced back to the middle of the 17th century, it was in the course of the 18th century that this method was perfected. The engraver Frantçois-Philippe Charpentier announced in the "Avant-Coureur" of the 10th of July 1762 that he had invented a machine "to engrave in a way that imitates wash processes". In 1780, Jean-Baptiste Le Prince, painter, drawer and engraver, whose sepia drawings had had great success, decided to reproduce them by means of engraving and consequently presented a paper to the Académie Royale de Peinture (Royal Painter's Academy) entitled Plan du traité de la gravure au lavis (Outline of a treatise on wash engraving). However, and despite Le Prince's personal success, his method had very little success in France and it was only quite some years later, after having undergone various modifications abroad, that aquatint returned to France at the end of the 18th century to occupy a place of honor. The term aquatint was coined in London during this period of exile.
In the second half of the 19th century, when great innovations were being made in modern printing, aquatint suddenly had an unexpected development. Attempts were made to adapt this technique to the newly discovered photographic processes. Niepce had already tried to transfer photographs unto metal plates so as to make engravings. His first "heliographies" date back to 1827. In his experiments the inventor of photography used a photographic negative and syrian asphalt*, which, when exposed to light protected the plate on which it had been spread. The non-exposed parts could then be dissolved without any problems thus exposing the plate in the same places. All that was left to do was to bite the plate. After biting the protected parts of the plate became the black areas of the printed picture.
Further developments in photographic techniques made aquatint one of the finest of all reproductive processes. As of 1878 Karl Klietsch of Vienna used these new techniques to invent grain photogravure. In 1882, when the first half-tone screens were invented (described below), the graining process of photogravure was abandoned. It was finally in 1910 that photogravure printing on a rotary press was developed thanks to the possibility of making engraved cylinders. Needless to say the appearance of such cylinders was fundamental in increasing the speed of printing. This transformation of the aquatint process is further discussed under the heading of photogravure since photogravure has also played a relatively important role in the history of print making.
THE TECHNIQUE OF AQUATINT.
Making an aquatint entails the following steps: preparing the plate, graining the plate, biting the plate, and, finally, printing it.
A. PREPARING THE PLATE. The plate* is a metal sheet which, once engraved, becomes a printing element. It may be made of steel, zinc, or copper. Copper is better for quality work as it is easily worked, has a high coefficient of tackiness for ink, resists the wear of repeated impressions quite well and can also be steelfaced. The plates usually used are 1 mm thick and are perfectly planed and square. The edges and corners should be slightly bevelled. If several plates are used, as in colour printing, each one of them must be exactly like the other.
The first step in preparing the plate is to pumice it. It is not necessary, however, for the metal to be polished. In some cases a mirror-like reflection might be rejected in favour of a slight grain, a mat polishing, or even a "un-polishing" done with a fine abrasive substance [* polishing]. In fact, a mat finish will hold ink better and allow for more nuanced half-tones while perfect whites can be had by using a burnisher* as in mezzotint* work.
On the other hand scouring the plate is an essential step as any trace of grease will work against the rest of the print making procedure [ * scouring ]
It is always best to protect the plate's back and sides (and in some cases the borders of the front) against the mordant, before the plate is grained since the grain is very delicate and will be harmed by coming into contact with or being placed on a surface. As the image on the plate sometimes coincides with the grain the plate can be protected and covered even hefore proceeding to draw on it.
Once the plate has been prepared it can be drawn upon. From this point on the artist must be careful not to touch the image surface of the plate with his fingers. It is a good idea to always place the plate on a slightly larger surface so that it can be turned at will. Furthermore, the use of a handrest will help avoid many problems [ * handrest ].
As in all etched work, the general principle is that those parts of the plate protected from the biting process by means of a ground or an appropriate paint will, after biting, print white whereas all the other areas (which have not been protected) will print varying shades of black. The quality of the different blacks obtained will be in function of the biting time and the type of surface bitten.
The image produced on a plate can be either a positive or a negative one. A positive image is a black design on a white background while a negative image is a white image on a black background ( white line work) A positive image can be obtained in much the same way as any etching, that is to say by removing certain parts of the ground covering the plate with a blunt etching needle. The ground may also be removed with a brush dipped in turpentine, in a mixture (used by Le Prince) of olive oil*, turpentine and lamp black, or with yet other mixtures [* ground removing]. Negative images are made in the opposite manner by covering the parts that must remain white with either a stopping-out varnish, an acid resistant paint (acrylic paint or a glycerophtalic paint, for example), ink, lithographic crayon or an oil-base pastel. In A Treatise on Aquatint I spoke of applying acrylic paint with a brush and then removing or drawing on this ground (where so desired) with a damp piece of wood. In the same book I also spoke of using an airbrush to spray paint or dilute the ground in order to achieve nuances and half tones [* grain]. Insofar as the drawing of an image is concerned (which is not specific to aquatint only) the reader may consult this dictionary under the heading etching. However the drawing is done it must, of course, be done in reverse so that the printed result will be pointing the right way.
As has been mentioned above, aquatint is characterized by and may be distinguished from other etching techniques by the fact that is has a grainy surface. This grainy surface is made up of little hollow dots spread on the metal plate which result, after printing, in the grain* of the image. Once the line work has been done the artist proceeds to create such a grainy texture in two successive steps. First of all he does the graining* and then he bites* the plate. Both steps are quite delicate and must be coordinated.
B. GRAINING THE PLATE. The purpose of graining is to protect the plate during the biting process in such a way that the biting forms a series of little hollows. The parts of the plate not protected by the grain will be bitten by the mordant. Hence it should be quite obvious that the quality and degree of the grain depend on the graining. When graining the artist must keep in mind that the goal of his work is to create areas that are pockmarked with holes of varying depth which will retain ink. Therefore the roughness, the spacing, and the depth of the grainy texture should be in function of the desired result. Values can be obtained by superimposing layers of grain, in a selective manner, as if one were repeating the graining.
As was the case in positive and negative drawing there are positive and negative grains.
The grain deposited on the metal plate will, in this case, be bitten and will thus result in black dots when printed. The most commonly used method to achieve such a result is the lift ground. When the ground (applied with a dabber and diluted somewhat with turpentine so that it will not dry too quickly) is still lukewarm, dust the areas to be grained with a water receptive agent such as salt, sugar, flower, fine grained sand, lamp black, powdered hone dust, sawdust, cork dust, etc. which must be quite dry. The regularity of the grain will, of course, depend on the regularity with which such dust has been distributed as well as on the fineness of the dust used. The dust must fall from a certain height, in a draft free room, when the ground still looks like a sheet of oil. The reason for which the dust must fall from a certain height is that it must embed itself well into the ground so as to come in contact with the plate. Then proceed, without waiting for the plate to be completely cooled off or for the ground to be dry, to plunge the plate into a basin full of clean cold water ( rain water being the best suited for the purpose). Remember to change the water in the course of the washing. The water makes the dust particles enlarge and thus cracks the ground immediately around it. As a consequence the plate is then exposed in a dotted pattern which need only be bitten to obtain the holes required for printing. If the artist is in a hurry or is only making a test, the plate can be plunged directly into the mordant bath which first will crack the ground and then proceed to bite the plate. It is also possible to create a positive grain by attacking the metal directly (with or without ground) with a tool such as a roulette or with an abrasive substance [*granulated plate surface]
2°)NEGATIVE GRAINING. Three methods of graining will be described in this section; the traditional way of graining with raisin or asphaltum, a negative spirit ground process, and a process I described in 1975 in L'Aquatinte à l'Aérographe (A Treatise on Aquatint) which allows for passages between half-tones.
- THE TRADITIONAL GRAINING METHOD WITH RESIN OR ASPHALTUM. This is certainly the most often used system and was first perfected by Le Prince. It consists in taking some very fine resin or asphaltum powder and putting it into a bag made of two to six layers of muslin cloth depending on the fineness of grain required. A rapid way of doing the same thing is to let the dust fall onto a brush and stroke it to project the grain onto the plate. The resins used for such work are copal, colophony, and sandarac. The drawback of colophony is that it glues into clumps with the slightest humidity. For this reason sandarac is usually preferred, even though it is more expensive. In any case, colophony (which melts more easily) is needed when graining zinc plates since zinc must not be overheated. It is often best to use powdered asphaltum* rather than resin since it spreads out less when heated, gives more beautiful blacks, and resists the mordant better. Its defect is that it is not transparent, which means that it hides the drawing made on the plate.
"Dusting" is done from a certain height in a draft free room. Some aquatintists used to cover their copper plates with a thinly spread viscous liquid made up of sugar, soap, and a bit of water. The purpose of this mixture was to fix the deposited dust.
A very regular distribution of the dust on a plate (expecially if it is a large one) can only be achieved by using a dust box or aquatint box. These boxes are quite large and their average size in centimeters are 150 to 200cm high (4 1/2 to 6 ft), 80cm wide (2 3/4 ft), and 60 to 100 cm deep (2 to 3 ft). The size is obviously related to that of the plate to be grained since the plate must be placed inside the box. The box must be hermetically closed except for one side, which is where the plate is introduced upon a tray. This opening must have a door in order to close the box. Furthermore, the box should be lined with oilcloth or zinc so that the resin dust will not stick to the sides. Place a little plate of calcium chloride in it on the far side of the box in order to absorb any residual humidity [* attacking agents].
The principle of the dust box is to contain a kilo of resin dust which is dispersed inside the box by a jet of air. The jet of air can be made with either a bellow mechanism or with a fly-wheel. This kind of graining method requires a certain amount of attention to minute details. In fact, since the larger dust particles settle first one must calculate a waiting period that will ensure the fineness of grain desired. Generally speaking one minute of waiting time will result in a fairly large grain, three minutes will give a medium grain, whereas five minutes will give a fine grain. Longer waiting periods will give a very fine or even an extremely fine grain. Once the plate is introduced into the box it must be left for five minutes if the dust used is large-grained and longer if the dust is fine-grained. Generaly speaking, if the dust is not very abundant, whether it be big or small-grained, it will usually permit a widespread biting of the plate and will therefore result in a rather dark printing plate. On the other hand, an abundance of dust will over-protect the plate, which will then he underbitten, and the result will be a gray tonality when printed. The theoretical combinations using the same amount of biting are as follows:
- a large grained dust used in a relatively small quantity will result in a sharp but irregular granulated surface.
- a large-grained dust used generously will result in a granulated surface that is not very sharp (the dust ground tends to flatten out and spread when heated).
- a fine-grained dust ground used in a relatively small quantity will result in a sharp and relatively regular granulated surface.
- a fine-grain ed dust ground used generously will result in a granulated surface that is not very sharp (the quantity used, when excessive, tending to blanket the plate).
A scant dusting can be followed by a second dusting and biting only if the first one was done with a fairly large-grained dust ground. The reason for this rule is that a fine-grained dust spread sparingly gives just a vague gray tonality when printed.
The next step in graining is to heat the deposited dust ground (this is a relatively delicate step) so as to fix the dust to the plate. In fact, while the resin or asphaltum dust was being deposited on the plate it was enclosed in a draft free space which protected it from any other dangers. From now on this will no longer be the case. When extracting the grained plate from the dust box care must be taken to touch only the second plate upon which it is resting. It need hardly be said that finger marks must not be left on the edges of the grained plate. The second plate (on which the grained one rests) should be of some metal which will facilitate the heating process since in this case one can place both plates together onto the hot* plate, grill, or oven where they will be slowly heated to the appropriate temperature. A second metal plate also has the advantage of helping distribute the heat equally under the grained plate. Such a distribution of the heat is essential for good results but is sometimes quite difficult to achieve with large plates. In the past it was quite common to heat the back of the plate with a naked flame but in the past there were also margins which could be gripped with wooden pliers held in the left hand while the right hand moved the flame back and forth. At present margins are not used and work on the plate ends at its very edge, thus excluding the above mentioned method. Nevertheless, one will have to be able to move the flame quite freely beneath the plate since the grain sticks to the plate almost instantaneously and because the heating should never be prolonged beyond the minimum time necessary.
The heating of the plate must be quite precise: neither too much nor too little. The artist must keep in mind that the grain always spreads out a little when heated. When over-heated and thus too spread out,each particle will tend to merge with its neighbors and clog the grain. On the other hand, when the heating is not sufficient the grain will not stick to the plate and will come off during the biting.
One way to tell if the ground has been properly heated is if its colour changes. The downy aspect of a dry dust ground turns into a semi-brilliant and transparent silky texture through which the plate itself can be seen. It is at this point that the heating process must be stopped. A properly heated dust ground can be recognized by a slight "settling" of the grain which can be seen when magnified. In fact, as we already said, this settling must he taken into account by the artist when he is graining a plate. A well-heated plate must be able to withstand a mordant during biting. After heating, the plate should be laid on a cast-iron surface or on a lithographic stone until it has cooled down. Once all this has been done the biting process can be started.
- SPIRIT GROUND CHAIN. This method of graining a plate was invented at the end of the 18th century. It consists in spreading a grain suspended in alcohol onto the plate. At first the resin to be used is saturated in 45° alcohol (about 90 proof) and is then mixed in the following proportions: 1/10 of this preparation and 6/10 alcohol. Such a mixture will produce a medium grain but, if one wishes to, the proportions can be changed in function of the grain desired. After the alcohol has evaporated the plate will be regularly grained. To hurry things up the plate can be slightly heated making sure that the flame never comes into direct contact with the alcohol. In order to achieve a greater homogeneity of the dust ground the plate can be put into a basin and covered with the above mentioned solution. Once the liquid has stopped moving and the particles have settled on the plate the plate can be lifted out of the bath with utmost precaution. This must be done by picking up the second plate it is resting on. Once removed from the basin, both plates can be placed on the hot plate so as to fix the deposited grain. The heating is done in the same way as described above (in I.) except that it must be done more gradually. It may be pointed out, but not recommended, that ether has been sometimes used as a substitute for alcohol.
- GRAINING WITH AN AIRBRUSH. Unlike the graining methods described above, which only allow for regular and solid colour grains, the specific technique I have developed for graining with an airbrush produces subtle nuances. For example, by using an airbrush one can obtain a heavily grained top of the plate and a lightly grained bottom with a progessive fade* between these two extremes. Furthermore, an airbrush grain can be extremely fine and can mix with the half-tones of a drawing in one operation. The only difficulty is the installation of the equipment needed. The airbrush itself is a little spray gun which is usually reasonably priced but it needs a supply of compressed air or a compressor. The artist must decide whether to use bottles of compressed air or a compressor. A full description of the airbrush* will be found in A treatise on Aquatint.
When using an airbrush for printmaking the air pressure should be set at 1,5 kg/cm2 (about 21 lb/in2). The fineness of the grain increases in proportion to the pressure but also in function of the nozzle opening, which can be regulated. The liquid to be vaporized must be well diluted, neither pasty nor viscous, and mixed in a perfectly homogenous way. The jet should be directed onto the plate from 20 to 30cm away (8 to 12 inches) at a pressure of 1,5 kg/cm2. If a finer grain is desired the distance can be shortened while for a bigger grain the distance should be increased. Both acrylic paint and stopping out varnish can be used with an airbrush although the latter will result in a much finer grain. Acrylic paint is diluted with water while the varnish will be diluted with turpentine.
Place the plate to be grained on a large sheet of white paper on a table making sure that the sheet of paper can be moved around freely. Set the let and try it out on a corner of this paper before using it on the plate itself. The spraying should be done at an angle of about 45° to 60° and in the most regular way possible. In case the entire plate cannot be grained from a fixed point the spraying can he done with a regular back and forth movement, first from left to right and back again, then by spraying up and down. The spraying should be slow and regular. The grain can be seen on the sheet of paper near the edge of the plate. In fact, it is very hard to see the grain deposited on the plate and it is easy to think it is not thick enough even when it is far too heavy. It is for this reason that one should keep the pieces of paper used and write down (in the white space left by the plate) all the necessary information concerning that particular graining. These sheets become the printmaker's best work documents. The paper used for this purpose should be quite smooth, very white, and always of the same quality. During the graining the artist should turn the paper, with the plate resting on it, a quarter of the way around its axis so that the jet will spray onto each side and border in an homogenous way. The areas to be heavily grained are, of course, sprayed longer. The grain is then checked, with a line-tester, along the edges of the plate. Stop the graining, before it reaches the saturation point, when the spaces between the grain are of the size required for the biting process. A certain amount of experience is required and it may be suggested that a few small experimental plates be grained varying the pressure, the liquid used, the spraying angle, the jet pressure and the spraying time. All of the relevant data should be noted on a sheet of paper for future reference.
After such tests larger plates can be safely grained. In order to see the grain as it develops during the spraying use a coloured acrylic paint which need not be dark but should be visible on the paper. Orange or yellow suit this purpose. Etching ground used with an airbrush is, on the other hand, quite visible. This ground is prepared by filtering a good engraver's ground and then diluting it with about 1/3 the amount of turpentine. When the graining has been done it would best be left to dry over a period of twelve hours or, in the worst case, at least one or two hours. After each work period the airbrush must be cleaned immediately by spraying the solvent used in the mixture: turpentine for the ground, water for fresh acrylics, and acetone for dried acrylic paint. A proper cleaning of the airbrush can be achieved by opening and closing the nozzle of the airbrush with your finger. This causes air to be mixed with the liquid and form air bubbles in the solvent, thus cleaning out the ducts.
C. BITING THE PLATE. This is probably the most delicate operation in the aquatint process. In any case biting can be done with two different mordants: nitric acid and iron perchloride. The former is usually used for zinc and steel plates but can also be used on copper (Le Prince often used it in such a way). The latter, although it can be used on other metals, is usually reserved for biting copper. It was thanks to grained photogravure that this acid was given its place of honor because it soon became obvious that, depending on its concentration, it has an effect on both metal and the light sensitive surfaces (such as gelatin) used in various photographic processes [*photogravure]
1°) BITING WITH NITRIC ACID. Nitric acid is a strong and dangerous acid whose fumes are harmful. Due to its strenqth it bites rapidly. A description of this acid and the way to prepare a mordant with it will be found under the heading attacking agents. When it is used on zinc or steel its concentration is usually lowered to about 10° since it bites slowly at 5° and rapidly at 15°. A slow biting process respects the grain and the drawing on the plate. At a concentration of 13° or 14° the grain begins to show signs of damage after five or six minutes of biting. One must, therefore, be careful and it will be found that beginning biting with an 11° or 12°B mordant (which can always be strengthened during the biting process if necessary) will give the most satisfactory results. Let me remind the reader that a slow biting generally tends to dig deeply while a rapid biting tends to corrode superficially. As a consequence finely grained plates must then be bitten slowly if they are not to be damaged.
A blackening of the metal plate is an obvious sign that the biting is underway. If the plate blackens immediately it means that the mordant is probably too strong. In any case, for aquatint biting the operation is never prolonged until the plate "boils" (i.e. bubbles rapidly). Furthermore, the bubbles must never be removed in any other way than by moving the pan in order to create a continous succession of waves which will wash the surface bubbles away. One must not, as in normal etching, use a pigeon feather* or a badger-hair brush* to brush the plate surface. No matter how lightly it is done, the grain would not resist such a brushing or feathering without showing traces of it. In aquatint the mordant must just reach the level of the plate so that the waves will successively cover and uncover it as they go back and forth. The pan must be quite a bit larger than the plate as this will help in carrying out the operation. Another precaution worth taking is to place the plate to be bitten onto another, larger one (plastic works well in this case) which will enable you to move the first plate more easily. When the biting has reached the required degree, remove the plate rapidly (making sure not to touch the image side) and rinse it thoroughly with water under a nearby faucet. If one wishes to have maximum depth of grain, the right amount of biting is just before the grain begins to deteriorate. Deterioration is shown by the excessive blackening, the beginning of "boiling", more numerous bubbles on the borders than in the center of the plate, the grain beginning to lift, etc. For further details not specific to aquatint see biting.
It may be of interest to the reader to know that Le Prince used nitric acid on copper in the following proportions: 1/4 acid 3/4 water for a slow biting mordant and 1/3 acid 2/3 water fur a strong mordant.
2°) BITING WITH IRON PERCHIORIDE. Iron perchloride is quite different from nitric acid. It bites slowly but also more deeply and with greater precision. Prepare 46°, 41°, 36°, and 33°B solutions of this acid to bite both copper and zinc plates but remember not to use one solution on two different metals and to keep them separate. With such a range of concentrations almost any kind of biting can be done. Each flask containing a solution should be properly labeled. Biting should he done in a dry place at a constant temperature (around 18 to 26° Centigrade - 64 to 68° Fahrenheit). The solution most often used is the 46° one which is thick and viscous and bites the grain deeply without damaging it. The lower concentrations bite more rapidly and therefore the plate exposure to the mordant must be reduced. For example, biting should not last longer than 5 or 6 minutes with a 33°B mordant (whose action is rapid and superficial ) whereas a 46° solution can be left to bite the plate as long as twenty minutes. In actual fact the 33° solution is only used for a quick scouring job or to make the plate uniform. It is best to begin the biting with a 46° solution which is then speeded up with a 41° or even a 36° solution. However, one can use the same solution throughout the biting process if one so wishes.
The precautions to be taken with iron perchloride are the same as with nitric acid insofar as the back and forth rocking of the pan is concerned. The use of a fairly large pan is recommended as an ample amount of mordant helps to disperse the used acid which always hinders the work of the rest of the mordant. However, iron perchloride is quite dark and thus makes any checking on what is happening rather difficult. To counteract such difficulties one should make sure not to let the mordant cover the plate by more than a few millimeters. For this reason, and also to facilitate the washing of the waves over the plate, make sure that the level of the mordant just reaches the plate.
Once the biting has begun, the pan must be rocked back and forth so that the black liquid produced by the biting washes off the plate and is followed, without interruption, by a wave of fresh mordant. A 46°B solution will give a very light grain after five minutes of biting, a somewhat stronger grain after ten minutes, and a black printing grain after fifteen minutes. It is dangerous to bite any longer than twenty minutes. The borders of the plate constitute a good warning system against excessive biting since they are the first to lose ground. If they begin to show signs of boiling the plate must be immediately removed from the mordant. When the biting is finished remove the plate (making sure not to touch the image side) and rinse it with water under a nearby faucet. The rinsing should be thorough. For further details on iron perchioride and its characteristics see the entries attacking agents and biting.
D. AQUATINT PRINTING. After biting, the plate must be cleaned. Ground is removed with turpentine whereas acrylic paint is removed with acetone. The plate is often somewhat oxydized when taken out of the mordant bath, in which case it should be cleaned with some metal polish and a relatively firm (but not stiff) brush which will penetrate the grainy surface of the plate. The metal polish should be diluted with some turpentine.
Generally speaking the printing of an aquatint plate is much like that of any etching. For details on the various steps see the entry etching (printing of - ). Below are some details as to the specific printing practices concerning aquatint.
First of all prepare the paper to be used in printing aquatint plates. The paper used must be quite heavy in order to take the grain. A good weight to be used is 250 gram paper. The dampening of the paper must be thorough and can usually be done overnight unless one wants to use Dutch paper (Van Gelder) which needs to be dampened less. Paper should not be taken out of the soaking basin more than ten minutes before use. When withdrawn from the basin it should be hung above it and left to drain off its excess water. In very hot weather be careful that the top of the sheet of paper does not dry faster than the bottom. It is essential for the sheet of paper to be evenly wet and that when it goes to press it be as supple as a rag. Due to these requirements multi-colour printing presents certain problems which will be discussed below[* dampening (paper), paper].
The second step is the preparation of the ink*. The artist will choose a special ink for etching of which there are various types. Some stick to the plate better while others are wiped off more easily. Ink taken out of a box or squeezed from a tube is not ready for use since it needs to be worked and diluted with a spatula and some oil. Keep a mixture of raw linseed oil (100 cm3) and thick oil (30 cm3) in reserve [*oil]. It is, however, obviously up to the printer to find the right consistency of ink for the impression he wishes to achieve, the paper used, the grain, etc. Generally speaking the ink should splatter a little when it is hit with a spatula. Too dry an ink sticks to the plate and is hard to wipe, too liquid an ink lacks colour and results in a moiré effect, and an ink that is too oily will stain the paper[* ink].
After these indispensable preparations, the artist can move on to the inking* of the plate. Even though the ink is oily it is necessary to prepare the grain to receive it by oiling the plate with vaseline oil (as used to be done in photogravure) or with glycerine. It is essential that this oiling be done well and be properly worked into the grainy surface of the plate by hand. Gently wipe the prepared plate with tissue paper. Then spread the ink onto the surface of the plate (which has been slightly warmed on a hot plate or which is warm due to its being used in a well-heated studio). The ink must penetrate the grainy surface well as of the first application.
While on this subject it must be pointed out that a hard dabber should not be used as it will damage the grain. Use either a tarlatan bail or a soft leather dabber. Do not "stuff" the ink into the grain by hitting the plate as for intaglio etchings. The ink should be pushed from the center towards the periphery of the plate.
Once the plate has been thoroughly inked proceed to the delicate task of wiping* it. A good impression depends on a proper wiping of the plate.
Prepare three halls from strips of tarlatan anywhere between 30 and 50 cm long depending on the size of the plate. Remember to work the cloth with your hands so as to make it lose some of its stiffness. The first ball is used to do a rough wiping and to spread the ink evenly over the surface of the plate. The surplus ink should be brushed towards the corners of the plate so as not to tear the tissue. The second ball is used for a cleaner wiping of the plate which should begin to reveal the whites. The last ball will finish wiping the whites. Tarlatan has the avantage of staying on the surface of the plate and not pulling the ink up out of the cavities. The difficulty of wiping lies in the fact that the extra ink must be wiped off without removing the ink in the lines and grain since that would spoil the print. However, if the plate were to be printed at this point the whites would be unclear both along the borders and all over their surface. The wiping must therefore be continued. The traditional way of finishing a plate was what in French is called paumaqe and in English palminq* (both being derived from the word palm) which means cleaning the whites of the plate using one's palms and hands each time cleaned on a printer's apron. Personally I do not recommend "palming" for aquatints since this method tends to slur the grain. The following method is better suited to our purpose. Prepare a pile of tissue paper approximately 20 by 15cm. Not any tissue paper can be used and especially not those that are particularly absorbant. The best type are the Swedish sulfite papers which are acid free. They are the most expensive type of tissue paper but the job they do compensates for their price. The sheet of paper must be laid on the plate and moved about with a fine sponge (pressed down with a middling pressure). When the sheet of paper is dirty it must be either thrown away or turned around. It takes five to ten sheets of paper to finish wiping an average sized plate. The last few sheets will hardly show any traces of ink. In any case the whole plate must be wiped including the blacks. The grainy texture must, at the end of the wiping process, show up as a homogenous and velvety surface. If the grain shows signs of the wiping it must be cleaned all over with tarlatan followed by tissue paper. The wiping of an aquatint plate must be absolutely clean and any retroussage* should be avoided. In fact, while dragging-out techniques can be experimented with in intaglio etching, a grainy texture does not react well to retroussage as it results in a clogged grain, spottiness, and irregular impressions.
Before printing one must clean the edges and borders of the plate as well as the back. If there are any margins these will also be cleaned before printing. This last step can be done with a clean cloth slightly wetted with some diluted soda or potassium solution. If the plate is of a small or medium size hold it by its back and if it is a large plate put it down in front of you. Remember that any finger marks on the grain will show on the impression.
Next, put the plate on the press bed. Printing an aquatint plate is much the same as printing any intaglio plate except for a few details. The blankets used in printing must be quite supple in order that the impression receive the grain. For satisfactory results I recommend using four layers of oilcloth ("skai ", for example) rather than the usual blankets. When using such cloth make sure that a cloth side touches the paper and a plastified side is in contact with the press roller. Insofar as the number of blankets (four) used in multi-plate colour printing is concerned please see the entry registering. Another detail to be pointed out is that an aquatint plate will print more satisfactorily if it is passed through the press twice (back and forth). For details on the rest of the printing process see drying and steelfacing.
The corrections one may need to make should be carried out with a burnisher* to darken the grain and an abrasive* substance to lighten it. Too clear a grain will have to be redone as the roulette* can only be used sparingly and then usually on the overly bitten margins. The regularity and mechanical quality of a roulette grain is not in the spirit of aquatint grain.
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