Etching the Plate: A Practical Guide
Bernice Cross etching a copper soft ground etching plate in a dip tank at RIT, NY
Backing the plate – Applying the handling strip – Etching in dip tanks (Edinburgh Etch)
Before a metal plate can be etched the back of the plate has to be protected by covering it with some kind of mordant resistant coating. Plates etched without this protection erode from the back developing heat and causing the grounds applied to the face to lift off. A very quick and reliable way to cover the back of an etching plate is to apply self adhesive tape such as strips of parcel tape.
MATERIALS
Products and equipment needed to back a plate:
rolls of parcel tape
thick sheet of acetate or thin plastic
blade cutter
cutting board
MATERIALS
Back a plate as follows:
1. Place your plate upside down on a cutting board. If your etch ground is very delicate, e.g.
if it has been aquatinted, protect it with tissue.
2. Stick parallel strips of parcel tape onto the back of the plate, making sure that the strips
overlap and that no metal remains visible.
3. Run your fingernail along the edges and over the overlapping joints to remove air pockets.
4. Cut off the excess tape with a blade cutter.
5. The plate is now ready to be etched if horizontal trays are used.
Plates that are to be proofed without replacing the backing each time, are best covered using a single sheet of adhesive film as this is less likely to retain etch solution underneath which can spoil the print as well as press blankets.
Etchers sometimes prefer to use liquid backings – in this case an even covering of stop-out varnish should be painted onto the plate.
Applying the handling strip
If the plate is to be etched in an upright dip-tank, a handle has to be attached for lowering the plate into the mordant.
This handling strip should be longer than the depth of the tank.
METHOD
Apply a handle as follows:
1. Cut a strip of acetate about 5 cm/2 inches wide and longer than the depth of the tankbeing used.
2. Attach the strip firmly to the back of the plate with several strips of parcel tape.
3. If large or heavy plates are being used, two handling strips are advisable.
4. In busy workshops where multiple plates are being etched, the top of a handling strip should be labelled to make identification simple.
Before etching commences the surface of the plate should be inspected for any greasy deposits. When an artist is working on an acrylic ground over many hours, it is often unavoidable that some greasy marks are made on the exposed metal. As grease resists the mordant it is possible that the biting process will be hindered in these areas. To make sure that the
whole plate erodes simultaneously, briefly immerse the plate in a bath of vinegar or citric acid.
Etching in dip tanks (Edinburgh Etch)
For most acrylic grounds an aerated compartment of a dip tank should be used. This gives a significantly faster and more responsive etch than an unaggitated compartment. Medium to coarse aquatints can also be etched in this way, but particularly fine aquatint dots require the use of a compartment of the dip tank with reduced or no aeration. Alternatively, an aquatinted plate can be etched in a tray to ensure that the acrylic granules are not damaged by the flow of the mordant.
The plate is held by the top end of the handling strip or strips and gently lowered into the etch solution. The back of the plate should, ideally, touch the wall of the tank so that the plate front is facing into the solution. It is best to suspend the plate in the solution rather than let it sink right down to the bottom of the tank where the etch may be slower.
A good way to suspend plates is to clip the acetate strip onto a tank divider using a plastic peg. In an aerated tank, the plate should hang about an inch away from the rising bubbles produced by the air pump – if bubbles are allowed to settle
on the plate they may etch craters into the metal. If a number of small plates are etched these can be stacked above each other on a single hanging strip to create more space in the tank. However, it is vital that plates do not touch and should never be sandwiched together as this may scratch the ground and impede the bite.
It is advisable to keep a record of the time when etching commenced. During biting, the depth of bite should be checked at regular intervals. For test purposes the plate is lifted out of the tank, allowing excess solution to drip back into the bath before the plate is carefully rinsed. Most etchers develop their own preferred method of assessing the depth of bitten intaglio, which of course is always judged with the desired effect of the final printed image in mind. A professional intaglio magnifier or a pocket magnifying glass gives a closer view of the indentations.
Another means of testing the depth is to carefully probe a bitten area with a drypoint needle; or a very small piece of the etch ground can actually be scraped off to reveal the eroded metal – these areas can be quickly mended by touching up with soft litho crayon before further biting is carried out. Acrylic hard ground plates are so durable they can even be test printed to assess the depth of bite, without having to remove the ground. After proofing the plate can be gently degreased and etched further.
When the plate is satisfactorily etched, it is rinsed thoroughly under running tap or hose. If more work is to be done on the etch ground, the plate is now dried by placing it in a hot air cabinet, near to a fan or by blotting dry. If the plate has reached its final stage, however, it can be transferred to a stripping solution after rinsing for the removal of the acrylic ground.
The right depth of bite is very much a matter for the artist to determine. When ferric-based mordants are used there is little danger of the kind of foul biting where acid works sideways as much as down. In most circumstances, the Edinburgh Etch or pure ferric can be relied upon to cut a clean wedge-shaped groove which resembles the mechanical cut of a burin.
In etching, always bear in mind that the narrower the opening in the ground, the quicker the etch tends to be. A wider area which does not produce a groove will etch slower because mordants work less actively in less confined areas.
The best way to build up experience and confidence in etching is to produce some test plates on which a variety of marks produced in different kinds of grounds are bitten from a few minutes through to a few hours. Test plates are also very useful when fine-tuning the many variables in the etching process e.g. mordant strength or agitation.