At Wharepuke I use ImagOn HD photopolymer film.
1. Plate Preparation – Prepare the plate by filing edges, sanding the plate with carborundum and de-greasing with soy sauce and whiting powder. Rinse and keep the plate wet.
2. 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).
3. 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.
4. Lay the film onto the wet plate and use a squeegee to flatten out any air bubbles.
5. Trim off any excess film and put the plate in a light fast drying cupboard.
6. Place an acetate image on the plate and expose under a UV light.
7. After exposure, remove the remaining top layer of film and 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.
8. Allow to sit for ten to thirty seconds then gently sponge the plate allowing for a total development time of two minutes.
9. 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.
10. 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.
11. If you wish to remove the polymer, immerse for at least 5 minutes in a stripping solution. Rinse thoroughly and dry.