Edinburgh Printmakers' Information

The Development of Photopolymer Printmaking

1. Polymer Photogravure: Photogravure was adapted for commercial use as "rotogravure", printing from etched copper cylinders. A related process was "flexography", using flexible plates moulded in relief. In the 1960’s rubber plates began to be replaced by nylon resin polymers. Today photopolymer "flexo" plates are used extensively for high speed printing in the packaging industry.
   Although photopolymers have been used extensively in commercial and industrial processes for many years, their use in fine art printmaking is relatively recent. Photopolymer makes photo-intaglio printmaking safe and easy to use. Other techniques are either complex (such as traditional photogravure) or use toxic chemicals as with solvent-based photo-resists.
   Some printmakers, such as Eli Ponsaing in Denmark and Dan Welden in USA, realised that photopolymer "flexo" plates could be used for photo-intaglio printmaking. The polymer reacts to ultraviolet light in much the same way as sensitised gelatine in gravure printing. When exposed to continuous tone artwork and printed as intaglio plates, they can produce prints comparable in quality with traditional photogravures. This new printing plate does not involve the use of acids or other hazardous substances in use. It develops simply in water and is therefore very safe to handle and use.
2. Preparing the artwork: As we are making a contact exposure, we need to begin with making a full-size positive (not negative) image on transparent or translucent material. Photographic images can be used and positives can be made in the darkroom on various types of film or produced digitally using computer scanning. The density and resolution of the positive image is crucial to the making of a high quality gravure print.
   The artwork can also be hand-drawn, using a wide variety of drawing materials and techniques ranging from simple crayon drawing to complex mixtures of painted tone and texture. In this case the image is generally produced on a special grained sheet of film (such as True-Grain) although tracing paper could be used with crayon, charcoal, pastel, etc.
3. Exposing the plate: At Edinburgh Printmakers we use Toyobo KM95R Water Washable Plates, exposed on an ultraviolet unit with a single 2-kilowatt light source (preferable to banks of tubes). Unexposed plates can be handled and cut safely in subdued light.
   First it is important to remove the transparent top sheet from the plate – this comes away easily. The film positive is then placed in contact with the plate (preferably using a vacuum) and is exposed to ultraviolet light. Ensure that artwork and plate are "emulsion to emulsion" – image side against the polymer layer.
   To find the correct exposure, make a test strip – begin by taping the artwork and plate securely to the glass of the unit and using a piece of black paper, gradually reveal more of the plate as you expose it in stages. During exposure, light passes through areas of clear film hardening the polymer. The opaque material of the image allows little or no light to pass through and these areas remain soft. When developing with water these are washed away, "etching" the image into the polymer. With underexposure, too much will wash away and the resulting image will be dark and ill defined. With overexposure, the polymer will harden too much and the resulting print will be faint with little or no detail.
4. Screen Exposures: With hand-drawn artwork or continuous tone positives the plate is then exposed to a random dot or "stochastic" screen. This creates a "grain " structure, which necessary for holding the ink, especially in solid black areas. Our digitally made screens have an extremely fine aquatint-like structure. To find the correct exposures, step tests are made combining several steps of the image exposure (running horizontally on the test plate) with a couple of different screen exposures (vertical steps).
   Following on from the image exposures, the artwork is removed (keep the plate face down on black paper or in a folder to avoid unnecessary exposure during the changeover) and the dot screen placed on the unit. The matt emulsion side of the screen is in contact with the polymer (remember "emulsion to emulsion"!) and one half of the plate is masked off with black paper prior to making the first exposure. After this, turn the plate around and make a new screen exposure, perhaps doubling the time.
   Finding the correct exposures is time consuming but once you have ascertained these, the process becomes relatively easy. There is reasonable latitude when it comes to exposing the plate – polymer plates need much more exposure than a film such as Imag-On Ultra.
5. Developing: After exposure, the plate is ready for developing. This is safe and simple – begin by filling a tray with water at approximately 25 degrees Centigrade. Don’t guess; use a thermometer! We develop in three stages, each lasting a minute. Wear gloves to avoid contact with dissolved polymer. One – place the plate in the tray of water and let it sit for one minute. Two – remove and gently rub the surface of the plate with a sponge under running water (preferably at 25 degrees) for one minute. Alternatively do this with the plate still in the tray. Three – hose the plate with water for a further minute.
   The plate is quickly dried using paper towels to gently blot the surface. Change the towels frequently and once it seems to stick gently to the surface when the water has been mopped up, dry the plate with gentle heat. After approximately 10 minutes the plate loses its stickiness and is ready for a final exposure to ultraviolet to harden the polymer for printing. Timing is not crucial but ensure that this exposure is at least as long as the image exposure. The plate is now ready for printing, though you could rub vegetable oil on it before inking up for the first time (to ensure that it doesn't stick to the printing paper).
6. Tips for printing: For printing, choose a soft responsive paper; Hahnemuhle Etching is ideal. The paper is soaked and dampened as usual. Use Graphic Chemical Easy Wipe Compound or weak copperplate oil in your ink when mixing to ensure it isn’t too stiff. The plate will scratch easily if there is any grit, so take care when inking up. Experiment with adding Extender/Transparent White as this increases the tonal range and can improve an otherwise murky print. The plates generally wipe easily, requiring soft scrim and a paper wipe with little or no heat
   As the edges can’t be bevelled, we usually have a margin round the image and print using a plastic mask with an aperture cut to the image size. You may need to adjust the pressure of your press; try printing with reduced pressure first. With traditional inks, clean the plates with vegetable oil and finish with a little low-odour turpentine to remove any traces of oil. Use the same procedure with water-based inks, as water will now damage the polymer. Plates are stored wrapped up, preferably in a dark cupboard in a dry area.

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Photopolymer films have two properties that are of interest to us as printmakers. First, they are sensitive to ultraviolet light and can be exposed using various UV light sources including sunlight. Second, they are extremely acid-resistant and when used as a photo-resist, even the finest of detail can be subjected to lengthy biting. Various types of film are available – Photec, Imag-On Ultra and Pure Etch are ones we have tested.

These films were developed for the production of printed circuit boards. Being a product for the printed circuit industry, these films are available in large rolls, often packaged in pairs. The polymer itself is light blue in colour and is sandwiched between two layers of clear plastic film. The inside protective layer is soft, resembling polythene, while the other layer is a more brittle cellophane-like material.

Mark Zaffron and Keith Howard, who introduced us to photopolymer during a workshop held at Edinburgh Printmakers in 1994, pioneered their use in photo etching and photo-intaglio. Since then, with the expertise and hard work of our members and staff alike, Edinburgh Printmakers Workshop has continued to research and develop this exciting new form of printmaking and has become recognised as one of the leading studios using this technique.

The technique is similar to that of polymer photogravure but plates can be exposed for conventional etching or the polymer itself forms the printing matrix in what we refer to as "non-etch" techniques.

A Quick Guide to using Photopolymer Film

1) 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.
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. Place the film in a lightproof folder to protect it.
4) 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.
5) 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.
6) 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.
7) 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.
8) 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.
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) ‘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.
12) If you wish to remove the polymer, immerse for at least 5 minutes in a stripping solution. Rinse thoroughly and dry.

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The practice of making art is not without risk. We use products that are potentially harmful or, even worse, highly toxic. In particular, traditional printmaking methods can expose the artist to considerable danger. Many chemicals regularly used by printmakers are classified as hazardous and some are suspected carcinogens. Nitric acid commonly used by etchers produces extremely dangerous gases that can cause lung disease. Asphaltum and rosin dusts used in aquatinting are potentially explosive. Solvents, such as white spirit, are harmful by inhalation or by absorption through the skin.

Artists worldwide have expressed genuine concern about the risks to their health, that of others and the environment. There is now a move to recognise these risks, to take adequate precautions to eliminate or minimise them and to find alternatives to solvent-based systems.

Edinburgh Printmakers has always welcomed change and, with increased awareness of the issues of health and safety associated with printmaking, we began to consider ways in which we could make our working environment healthier and safer. Since 1994 we have utilised safer etching systems - getting rid of hazardous chemicals and solvents used in the technique of etching. At EPW we’ve eschewed the terms "Non-Toxic Printmaking" or (worse still!) "Safe Etching". We feel these terms are misleading. Although a few of the materials we use are certified "non-toxic", the majority are still potentially harmful if misused. We always insist users wear suitable protection and follow the correct procedures when working with these techniques.

We were the first to refer to the system as "Acrylic Resist Etching". This encompasses a wide range of techniques using water-based etching resists. We’ve developed our own recipes based on years of experience, encouraged by a willingness to experiment. These resists are easy to use, clean up with water and are amazingly versatile.

At present we use copper and zinc plates for etching. We etch the copper in vertical dip-tanks containing ferric chloride. Zinc plates are etched in ferric (not Edinburgh Etch!) or copper sulphate. Once the plates are etched and printed, the prints look exactly the same as those produced by so-called "traditional" methods. Using water-based resists means cutting down or eliminating the need for solvents - the studio is a happier and healthier place.

We also use photopolymers extensively for both photo etching and "non-etch’" polymer photogravure. We use "Photec", a photopolymer film that can be laminated onto metal plates and etched. For "non-etch" we use the same film or Toyobo KM95R flexigraphic plates. Both can be used in an astonishing variety of ways working from hand-drawn, photographic and digital artwork. The flexigraphic plates are particularly useful for our editioning programme here at EPW as we can print large numbers from the processed plate.

Unfortunately many artists seeking to use our facilities have received little or no training in these methods (though they are now being widely adopted both in the UK & worldwide). This means that we positively encourage prospective users to undertake appropriate training with us before using the studio to guarantee safety for themselves and others. We have also worked with other studios and university printmaking departments in the UK and abroad to help them establish these safer working methods.

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Intaglio Printmaker, 62 Southwark Bridge Road, London SE1 0AS
Tel: 020 7928 2633
Fax: 020 7928 2711
Website: www.intaglioprintmaker.co.uk
Imag-on Ultra Photo-polymer Film (61cm x3.05m)
Aquatint/Half-tone Screens

Lawrence, 208 Portland Road, Hove, East Sussex BN3 5QT
Tel: 01209 313181
Fax: 01273 260270
E-mail: artbox@lawrence.co.uk
Imag-on Photo-polymer Film (61cm x3.05m)

Edinburgh Printmakers, 23 Union Street, Edinburgh EH1 3LR Scotland
Tel: 0131 557 2479
Fax: 0131 558 8418
E-mail: printmakers@ednet.co.uk
Photec Photo-polymer Film (per metre)
Random Dot Digital Screen

Nicoll Graphics, Openshaw International Ltd., Woodhouse Rd., Todmorden, Lancashire OL14 5TP
Tel: 01706 811 408 (Zoe)
Fax:08706 090 808
E-mail: gold@openshaw.com
Bulk suppliers of Toyobo KM95R Water Washable Plates (A3: £10.80 X 20)

Polymetaal is a Dutch supplier of printmaking materials and they specialise in photopolymer and acrylic etch products. Their website is helpful and informative: www.polymetaal.nl

Information on low cost UV units can be found at: www.megauk.com

Information about Photopolymer Gravure can be found on Strange Ross’ website: www.psy.ku.dk/ross/Ph_grav.html

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