ALTERNATIVE PRINT MEDIA 2001

Photopolymer Film

We use photopolymer film to transfer drawings, photocopies, photographs and computer generated stencils for intaglio prints. The thin film is sensitive to ultraviolet light. Before use, the film must be laminated onto the copper plate. The film is sandwichedbetween two layers of protective foil.

Lamination

Cut out a piece of film a little bigger than the copper plate. Make a cut across one corner with a sharp hobby knife (½cm from the corner). Tear off the corner. Pull off the soft inside foil. Place the film on a newspaper with the unprotected side facing up. Spray the film with a lamination solution from an atomizer. This solution is made by mixing 1 part of propyl alcohol with 3parts of water. Place the film on a perspex plate on the etching press bed (sprayed side up). Carefully lower the de-greased copper plate onto the film. Cover the wet edges with plastic. Run the plate through the press. Remove the plastic foil and cut off excess film with a sharp hobby knife. Store the laminated plate in lightproof wrapping until you need it.

The Line Drawing

The stencil must be transparent so you can study it on a light table. Place the laminated  plate on the vacuum frame. Place the line drawing on top. Turn on the vacuum and expose the plate in the UV light for 2-3 minutes. Take out the plate and remove the top foil by rubbing your hand across the edge of the plate. Place the exposed plate inthe developer (10 grammes of soda crystals diluted in 1 litre of water). Use a sponge in the developer as though you were washing the plate. After a couple of minutes with steady movement the image will appear clearly. Take the plate out of the developer, rinse it in running water and check the depth with the back of your hand. If it doesnot feel deep enough, develop it further. The image must appear clearly coppery in the blue photopolymer film. Rinse the plate, dab it in a newspaper and let it dry in the drying cabinet. Finally harden the plate in UV light for minimum 3 minutes. Ink up the plate and print it.

Photopolymer Etching

Images transferred to photopolymer film can, of course, be etched into the copper plate. Before exposing the photopolymerfilm, you need to thin it. Remove the top foil and save it for later. Now put the plate in a fresh soda developer under a lid for 20to 30 minutes. The developer thins the film evenly all over, except for the edges: they will disappear. The pre-developing timedepends on the quality of the water - that is, the amount of calcium in the water. This means that a test has to be made once andfor all and the plate taken up and checked at intervals. When small holes begin to appear in the film it has been pre-developedexactly 3 minutes too much. At the Printmakers’ Experimentarium the optimum pre-development takes 27 minutes at roomtemperature. When the plate is ready, take it out of the developer and rinse off the dissolved photopolymer film in cold, runningwater. Dab it quickly in clean paper and put it in the drying cabinet. The dabbing must be swift to keep the paper from stickingto the unprotected film.

The starting point in this case is a photocopy from a book. Rub the photocopy thoroughly with salad oil. Check the transparency on a light-table. Wipe off the excess oil with a piece of cloth and dry the photocopy in the drying cabinet. Thinning the Photopolymer Film Remove the protection foil on top of the laminated copper plate.

Place the plate in fresh developer (10 grammes of soda crystals diluted in 1 litre of water) under a lid for the optimum time. Take the plate out of the developer and rinse off the dissolved photopolymer film in cold, running water. Dab it quickly in clean paper and put it in the drying cabinet. The dabbing must be swift to keep the paper from sticking to the unprotected film. Transferring and Etching the Stencil Place the pre-developed copper plate in the vacuum frame and cover it with the protection foil you removed before thepre-development. (This prevents the film from sticking to the stencil). Now expose the photocopy for the time it would have required had it been a non-etching: The aquatint exposure + that of the washing. Take out the plate and cover the back with packing tape before development.

Place the exposed plate in the developer (10 grammes of soda crystals diluted in 1 litre of water). Develop very gently with just the weight of the sponge, since the photopolymer film is now ultra thin. Develop the plate 1-2 minutes with steady gentle movements all over the plate untill the image looks coppery. Rinse the plate in cold running water and dip it in ferric chloride for a few seconds. Where the image oxidizes the copper has been bared. Non-oxidized areas of the image must be developed further for example by using a cotton bud.

Repeat stages 4-7 until the entire image oxidizes.

De-oxidize in vinegar and salt, rinse, dab and dry the plate in the drying cabinet. Spray on an even layer of aquatint. Harden the plate for about 10 minutes in the drying cabinet. Stop out the bared edges of the plate. Harden the plate for another 10 minutes in the drying cabinet.

The plate is now ready for etching or print the plate as is.

Only washings, photocopies and line drawings containing bold lines have to be coated with aquatint before etching.This prevents open bites. Thin line drawings, half tone photographs, and digital images with halftone dots can be etched right away without a coat of aquatint.