A Quick Guide to using <techniques
Photopolymer Film –
Edinburgh Printmakers
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Plate edges should be filed. Prepare the plate by degreasing. Use a kitchen scourer and scrub the metal plate, as this will create a slight tooth to help the film stick evenly. Rinse front and back with warm water and dry under the hot-air drier. The plate can also be sprayed with a fine acrylic aquatint, as this will also help the film adhere. Ensure the aquatint is dry before moving to stage 2.
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Cut the film to size allowing a small margin all around the plate. Do this in subdued light or in a darkroom (yellow safe light).
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Strip off the first protective layer. The film has a natural curl - work with the film curl side uppermost. Attach sticky tape to one corner and peel back. After removing this layer, the film lies flat. Place the film in a lightproof folder to protect it.
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Laminate the film onto the plate using the etching press. This should be prepared by placing a sheet of Perspex or similar material on the bed. Ensure that this is clean and free from scratches and set the press at the right pressure to accommodate this. Remove the film from the folder and place onto the perspex with the stripped-off side uppermost. Place the plate onto the film and put a sheet of newsprint over the plate. Bring down the press blankets over the plate and run through the press slowly and evenly.
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After removing the blankets and newsprint slip the plate back into the folder. In safelight conditions trim the excess film off. It's easier to do this face down, using the edge of the plate to cut against. Dispose of any scraps.
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Use the UV unit to make the exposure (or sunlight, if this is not available). Read the section on exposing the plate in “Polymer Photogravure” for more information on this. Place the artwork in contact with the photopolymer. For an etch exposure, expose to the image only. “Non-etch” exposures will need a screen exposure, using the “random dot” screen.
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After exposure, slip the plate back into the folder and return to the darkroom and work under yellow light. The remaining top layer of film must now be stripped off. Place the plate face up in a tray of developer. To make the developer use 10g of soda crystals mixed with 1 litre of water - use at a temperature of between 20-25 degrees Centigrade.
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Allow to sit for ten to thirty seconds for an etch exposure or one minute for “non-etch”, then gently sponge the plate allowing for a total development time of two minutes.
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Now rinse the plate with cold water and use a squeegee to remove water. Blot dry with a paper towel. Ensure no water is left on the plate and leave to dry. Gentle heat can be used to speed dry.
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If you’re etching the plate, when the plate is dry try test bite it in the ferric or copper sulphate bath, depending on which metal you’re using. Bitten areas will darken. Return to developer if not fully developed. Rinse, dry and test again. Once the plate is biting as desired, after rinsing with water and drying it, harden the polymer by exposing it to ultraviolet again. Make this as long as the main exposure and a little more. You could also place the plate in sunlight outdoors until the polymer darkens in colour.
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‘Non-etch’ plates should also be hardened before printing. To avoid the plate sticking to the printing paper, rub with a little vegetable oil prior to printing for the first time.
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If you wish to remove the polymer, immerse for at least 5 minutes in a stripping solution. Rinse thoroughly and dry.
