In etching it is necessary to go through a certain set of preparations before the actual mark-making process can begin. In keeping with the tactile nature of the medium these processes are quite physical and more akin to the field of metalwork than to other paper-based image making. Preparing the plate is the first opportunity for the artist to engage in a relationship with the material he has chosen to work with to produce an art object.
Cutting metal plates
Most metal plates available from industrial sheet metal dealers are fairly large – single sheets of zinc or steel are usually about 4 ft x 8 ft – so in most cases cutting will be required to provide you with the required plate sizes. Industrial suppliers usually have their own cutting facilities and are often quite happy to cut large sheets into manageable sizes at hardly any extra cost. However, in any professional etching workshop, a sheet metal guillotine is a piece of equipment that is almost as important and as frequently used as an etching press. It enables etchers to cut any size of plate from larger sheets as and when required. Most freestanding guillotines are designed to cope with metal plates up to 1.5mm thick if the blades are kept sharp and properly aligned. A good guillotine should also come equipped with a clamping mechanism and a blade guard. Thinner metal plates can easily be cut by hand using aircraft metal snips, (nibbler), and there are also metal cutting attachments that can be fitted to any power drill.
MATERIALS
Products and equipment needed to cut metal plates:
sheet metal guillotine or metal snips
drypoint needle
measuring tape or ruler
heavy-duty workshop gloves
goggles
METHOD
Cut metal plates as follows:
Measure and mark out the perimeter of the required plate size with a ruler and sharp drypoint needle or the tip of a Stanley knife. This produces an incised mark that is much more precise than an outline drawn in marker pen.
Check right angles with a setsquare as the metal guides on a guillotine may not be accurate. Cutting plates with right angles and of matching size is particularly crucial in color etching as two or more plates are overprinted in exactly the same position on the paper. Always handle plates very carefully and wear heavy-duty gloves for protection from sharp edges.
If no guillotine is available plates can also be cut either by repeatedly scoring the perimeter lines into the metal along a ruler until the sheet can be broken, or by using an electric jigsaw or band saw with a metal blade. Make sure that the plate is firmly clamped down, wear goggles and lubricate the saw blade with plenty of oil. This way of cutting will produce a slightly serrated edge which needs to be removed by filing. There is a hand tool called a plate nibbler which can also be used to cut plates.
In workshops where sheet metal is being regularly handled minor cuts are almost inevitable. A first aid kit must always be readily available and include disinfectant which should be used on any cuts from rusty steel plates.
Filing/Beveling the plate edges
The edges of plates used in intaglio printmaking must always be broken and bevelled at a 45 degree angle before printing. This applies to all hard materials that you may use i.e. metal plates, Perspex, hard board or even thick pieces of card that are used for collagraph techniques. The enormous pressure exerted by the etching press during printing will cause any sharp edged object to cut right through the paper as well as the felt blankets which are expensive to replace and should be treated with great care.
MATERIALS
Products and equipment needed to apply a bevel:
metalworking file with fine and coarse sides
plate bevelling tool
sturdy metalworking bench or other work surface
three-sided scraper
power drill with sanding disc
clamp
sandpaper
gloves
goggles
METHOD
Apply a bevel to metal plates as follows:
1. Lay the plate down on the work surface and press down firmly with one hand.
2. Push the file in a downward motion along the plate edge at a 45 degree angle.
3. Repeat this action a number of times using the coarse side of the file first on all four sides.
Lift the file away from the plate during each upward stroke – it is less effective to move the
file up and down like a saw and doing this can damage the metal teeth of the tool.
4. Repeat this process with the fine side of the file.
5. Remove any remaining sharp edges by running a piece of sandpaper over the bevel.
6. A quick way to bevel very thin plates (under 1 mm) is to repeatedly run a three-sided metal
scraper along the plate edge at a 45 degree angle. Many printmakers now make use of a plate-bevelling tool instead of a file.
For projects involving a large number of plates, the bevel can also be applied using a power drill with a sanding disc attached to it. Precautions must be taken if you are going to apply the bevel this way – wear goggles and gloves and make sure that metal sparks do not come into contact with any flammable materials that may be present in the workshop.
Sanding the plate
Some, but not all of the mordant resistant grounds used in acrylic resist etching (such as liquid hard ground or photopolymer film), require a slightly roughened surface in order to bond firmly with the metal of the etching plate. This fine roughness is achieved by sanding the plate with medium grit sandpaper suitable for metalworking purposes. This process not only gives a tooth for the acrylic varnishes to adhere to but also removes minor scratches from the plate surface making the metal more susceptible to the corrosive action of the mordant in which it is etched. A sanded plate may produce slight plate tone in printing, but a white background is easily achieved by buffing up the plate after etching or by printing directly from the smooth surface of an acrylic resist.
MATERIALS
Products and equipment needed to sand a plate:
sturdy metalworking bench or other work surface
electric sander (ideally a palm sander with dust extractor)
medium grit sandpaper
G clamp
goggles
heavy-duty gloves
dust mask
METHOD
Sand metal plates as follows:
1. Put on a dust mask, gloves and goggles.
2. Secure small plates to the workbench using a G-clamp.
3. Unless you have pre-cut sandpaper, cut sandpaper sheets to fit the sander. Insert a sheet
into the clamping mechanism and, if needed, punch dust extraction holes into the paper.
4. Switch on the sander and apply it gently to the plate in a rotating motion. Do not apply excessive pressure as the weight of the sander is sufficient to roughen the surface of the metal.
5. Keep sanding the whole of the plate in regular orbits until you have produced an even, misted looking surface. The whole process should take no more than 3-4 minutes for a medium sized plate. Be careful not to over sand the plate as the aim is to roughen it rather than polish it. To avoid this, it is necessary to change a sanding sheet for a new one as soon as it begins to appear worn.
Use a finer grit wet and dry sandpaper (e.g. 360 grit) for copper and zinc plates.
Use a coarser grit (around 250 grit) for steel plates.
If a plate is designated for mechanical work only such as engraving, drypoint or mezzotint, without the involvement of any etching, no sanding or degreasing is necessary. When steel plates are used it is necessary to remove the protective grease deposit from the plate before sanding. This does not have to be as thorough as the main degreasing process and can be done quickly by wiping the plate with a rag using blue degreaser, then drying it. Sanding can of course be done by hand, but this is more likely to leave unwanted marks on the plate.
Degreasing
There are two reasons why all grease has to be removed from plates before any mark making can begin. In areas of the plate surface which are covered by an acrylic resist, even a very thin layer of grease can cause the varnish to lift off in the etchant, thus leading to unwanted biting. On the other hand, grease can in itself resist the corrosive action of the etch solution so that traces of grease left on blank metal areas that are meant to be eroded will actually stop this from taking place.
Degreasing in the acrylic resist etching system should ideally be a two-stage process:
Stage 1. Treat the plate with a powder degreaser mixed to a thick paste.
This absorbs grease even from the crystalline depths of the plate.
Stage 2. Degrease again with a liquid acidic degreaser as a final rinse.
This both ensures perfect degreasing as well as a slightly acidic plate climate which is favourable for the adhesion of all acrylic etch grounds and absolutely essential for photopolymer work. Marler-mesh degreasing powder, which was originally developed for screenprinting is very effective. Its very fine powdery consistency means it can even be used on burnished surfaces without scratching. Any domestic cream cleaner such as COMET is equally suitable as well as the slightly coarser magnesium carbonate powder.
An ideal product for the second stage is the blue CPS degreaser (or similar product) – an innovative and very powerful degreasing liquid which is slightly acidic and water/detergent based. This liquid which dilutes 1 : 10 parts water, is also well suited for all localised degreasing tasks on the etching plate i.e. just wipe a greasy surface with the CPS on a clean absorbent tissue.
Alternatively, diluted vinegar or citric acid can be used in the second rinse. Many workshops use concentrated dish soap as their main degreasing agent.
MATERIALS
Products and equipment needed for degreasing:
degreasing sink
drying facility
degreasing powder – ideally use Marler degreasing powder, alternatively use domestic cream cleaner, magnesium carbonate or whiting powder degreasing liquid – ideally use CPS liquid degreaser, alternatively use pure vinegar (with no added sugar) or concentrated dish soap.
small
window squeegee
latex or vinyl gloves
roll of kitchen towel
Facilities Suggestion:
The degreasing sink should ideally be a separate sink from those used for etching, rinsing or stripping purposes to avoid contamination. Traces of alkaline stripping solution left in a sink can break down the acrylic grounds when subsequently applied to the plate. The sink should have hot and cold water supplies from a flexible shower hose and be fitted with a wooden grid.
METHOD
Degrease metal plates as follows:
1. For a medium sized plate, mix about 1 tsp of degreasing powder with a little water to make a paste and apply this to the plate.
2. Use a clean pot scourer to work the paste into the plate surface using orbital strokes, applying firm pressure. (If a shiny rather than a sanded plate is being used, use a soft cloth or sponge instead.) Using the rotating motion, cover the whole plate as evenly as possible for between 2-5 minutes.
3. Rinse off all the remaining paste with plenty of hot water, making sure the front and back of the plate are thoroughly rinsed.
4. Rinse out the pad and apply a small measure of blue CPS degreaser (or alternative) and rub the plate before rinsing once again.
5. Stand the plate against the back of the sink and let water run over it. Water running evenly across the surface of the metal indicates a successful degreasing. If, however, the water meanders down the plate, some more degreasing will be needed.
6. Now the plate needs to be dried quickly to prevent any oxidising – especially on steel plates.
7. Squeegee off all excess water then dry off the plate using a hot air drying facility.
Alternatively, the plate can be blotted dry using grease-free absorbent paper (e.g. kitchen towel). From this point until application of a ground, be careful not to touch the degreased surface. Never use a hair dryer in an environment where wet processes are taking place. Wall- mounted dryers are a safe solution; and circuit breakers should be used.
At this stage you have completed all plate preparation and can now move on to the application of any one of the acid resistant grounds.