Photopolymer plates have been used in industry for many decades, (flexography), and the printmaker Dan Welden popularized their application in Fine Art printmaking, where they serve as a technique of photo-reproductive intaglio. The method allows artists to create rich and tonal images.
A range of industrial intaglio photopolymer plates is available, (cheaper plates may be more hazardous). Dan Welden's Solarplates are among the best researched, and most widely used.
The Solarplate process has similarities with Intaglio Type and other film based photopolymer methods, but here, the ready-made plates wash out in water rather than sodium carbonate. Both types of photopolymer process open up a range of innovative artistic possibilities, especially if used with a random dot screen, and solarplates allow for deeper intaglio. While dry photo-polymer films that wash out in soda ash, have a fairly well documented safety record in industry, there are questions over the VOC safety of certain kinds of the 'flexography-type' plates.
This is related to an older polymer chemistry, developed early in the 20th century by the printing industry, underlying many of these products. Although most plate manufacturers such as the Japanese firm Toyobo assure users of the safety of their water-wash plates, one needs to consider the fact that all these products are developed and manufactured for industrial use and machine processing.
Artists using certain kinds of plates in isolation may expose themselves to considerable hazards from un-reacted compounds, and it is best to process any plate with professional fume ventilation/extraction systems, and/or use a personal organic respirator to safeguard against exposure, even if there are few hazards that are documented for the product.
There is an astonishing variety of different photopolymer plates, mainly designed for mass printing applications in the packaging industry, and some kinds of water-based plate are higher quality and do suggest a degree of inherent safety in their (acrylic-based) chemistry.
electron micrograph of cross-linked polymers (Groce/Kiekeben/Greenwood –– UMaine, 1998)
In any case, many plate brands and processes have a significant environmental impact and may present hazards to users' health, if used incorrectly and without precautions. The main issue with some brands of photopolymer plate appears to be the presence of solvent additions in the emulsion in some, and hazardous compounds resulting from incomplete cross-linking of monomers in others. As a point of interest, this kind of VOC hazard is also common in cheap polymer-based products in general, including some inferior water-based paints and many kinds of plastics. Toxicity of Solvents
Today, big manufatcurers of photo-polymer products frequently cater for both the electronics and the printing industry (examples: Hitachi/DuPont/MacDermid).
see Intaglio Type for additional reference and sources on this topic.
Dan Welden explaining the solar plate process
The film Printmaking in the Sun documents Dan Welden as he makes solarplates at his studio in Sag Harbor. Welden lives and works in the Hamptons but also travels all over the world delivering workshops and sharing his expertise as a printmaker.
He trained in Germany as a traditional lithographer but has always had a love of experimentation and an interest in making printmaking more user-friendly. In the early 70s his investigations into safer and healthier methods led to the development of the technique now widely known as SOLARPLATE printing. Solarplate printing or etching used to be regarded as less toxic than traditional etching, but currently this notion is being questioned by some experts. All flexographic plates contain large amounts of unreacted monomers of various and complex chemical compostion, and the manual processing of these materials entail extensive exposure to potentially hazardous organic compounds. There currently is a discussion how to improve safe handling and protective measures for artists using 'Solar plate' type plates.
Dan explains how it works: "You can create a piece of artwork on a transparent film; overlay it on a solarplate and expose the film and plate together in the sun. Effectively you're transferring a drawn image to the plate and the plate can be used to print either in relief or intaglio."
The film shows Dan creating a powerfully fluid drawing on acetate using Graphic Chemical ink, various tools (including his fingers), and baby powder to give the image density in certain areas.
He enjoys the direct approach but goes on to explain that an image can be produced in many different ways:
"Some artists prefer to work in the darkroom with a photographic transparency. Others work with a computer; they scan images and print them out onto transparent film. Once we have that transparent film, that's what is used to create the plate. It's put in contact with the solarplate, exposed in UV light and then developed. Unlike traditional relief and intaglio methods, with solarplate printmaking there is no need to compose an image in reverse - the printed image appears with the same orientation as the original drawing."
Welden enjoys the freedom and flexibility of creating the image on acetate. With this material it is easy to add or remove marks, to create textures and patterns - and because acetate is inexpensive, if you don't like what you've done, you can simply start again on another sheet.
Dan completes two drawings on acetate - one to be relief printed, the other to be intaglio printed. Firstly, we see him demonstrate how to produce a relief solarplate.
How to make a Relief Solarplate
After Dan has finished creating an image on the acetate, he removes a light-sensitive plate from its folder. The drawing is placed face down onto the plate and a piece of glass is put on top. The whole thing is then sandwiched together using ordinary clamps that you can get from any hardware or home improvement store.
clamping the plate, drawing and glass
Dan carries the plate-acetate-glass "sandwich" outside and finds a sunny spot; preferably somewhere the sun will hit the plate at a 90 degree angle. A timer is set to a couple of minutes - the exposure time varies according to the strength of sunlight, the time of day, and the time of year. A delicate transparency needs less exposure time. He explains that:
"light will pass through this piece of film onto the polymer surface. This hardens the surface. Any areas that are not exposed, that are hidden by the drawing, will be automatically washed out in water."
After exposure the plate is taken back inside for the "wash out " or "developing" stage of the process. The glass is unclamped and the exposed plate is placed in a large tray that has a magnetised base. As the solarplate is steel, it holds to the bottom of the tray while being washed. The wash takes a little while because it is a relief plate and Dan needs to scrub all the way down to the metal, until the image is revealed. Copper-colored areas indicate the relief surface and the yellow marks are the lower areas.
Once scrubbing is completed, Dan thoroughly rinses the plate then blots it with ordinary newspaper before taking it outside once more to let it harden up.
How to make an Intaglio Solarplate
Next Dan demonstrates how to produce an intaglio solarplate. Firstly, the intaglio plate has to be exposed with an aquatint screen - a double exposure process created by Pauline Muir. The aquatint screen is a piece of acetate that has been machine printed with a pattern of tiny "squiggles". The light passes between the squiggles, which hardens about 20% of the plate. The emulsion side of the screen goes face-down onto the emulsion side of the plate which is face-up on the workbench.
checking for the emulsion side
of the aquatint screen
A clean sheet of glass is placed on top and the whole thing, clamped together. When there is not enough sun, Dan uses a light box to expose the film. He always exposes the screen to the plate for exactly 1 minute 30 seconds. Once the screen has been exposed it is removed and the drawing Dan made on the acetate is put in its place. The artwork is always exposed second and goes face-down on the plate before the glass is re-clamped. The plate is now exposed a second time. The length of this exposure is not standard - it is dependent on the nature of the artwork, and experience! Once exposure is complete, the plate can be washed.
The wash out on an intaglio plate is a little different to that of a relief plate. On the relief plate you can see quite clearly what's happening but with the intaglio plate, Dan washes it for about a minute and the image is only visible after blotting. As with the relief solarplate, he puts the intaglio plate outside to become fully hardened before printing.
inked and wiped intaglio solarplate
The remainder of the film shows Dan inking up the relief plate using a hard roller before putting it through the press; then inking and wiping the intaglio plate before producing the finished print.
rolling up the relief solarplate
For anyone interested in learning about Dan Welden's Solarplate printmaking, this DVD makes a great introduction. It demonstrates how a printing process can be made simple and safe, and still result in artwork of the highest quality and variety.
Solarplate or Flexography Plate Safety:
There are some suggestions that in some instances there may be
chemical exposure hazards not fully documented,
especially with cheaper kinds of flexography
Dan Welden further explains (2012):WE BELIEVE THAT SOLARPLATE ARE A SAFER PRACTICE THAN MOST OTHER SIMILAR PRODUCTS. WITHOUT SOUNDING BIASED THE RESULTS CAME FROM AN INDEPENDENT LABORATORY THAT TESTED OUR PLATES AND GAVE THEM AN ASTM D-4236 RATING. AT THIS POINT I BELIEVE IT IS THE ONLY POLYMER PLATE WITH THIS APPROVAL.THIS STUDY HAD BEEN PROMPTED BY SOME OF THE COMPETITION THAT CLAIMS TO BE SAFE. HAVING USED ALMOST EVERY POLYMER PLATE ON THE MARKET, I KNOW THAT SOME CAN CAUSE ILL EFFECTS. THIS IS WITHOUT QUESTION AND HAS BEEN A POINT OF CONTENTION WHEN I ATTEMPTED TO HAVE A JAPANESE COMPANY CHANGE THEIR FORMULAS TO A MORE SAFER CHEMISTRY. THERE WAS OBVIOUSLY NO SATISFACTION SINCE THEY SAID 'THESE PLATES ARE NOT MEANT FOR ARTISTS AND THE WAY YOU USE THEM. THEY ARE MEANT TO BE PROCESSED DIFFERENTLY THAN BY HAND SCRUBBING' WITH THAT, I DISCONTINUED SUPPORTING THE PRODUCTS THAT I HAD BEEN USING AND HAVE BEEN WORKING WITH AMERICAN MANUFACTURED PLATES.
Some thoughts on the waste water from
photopolymer plates / environmental impact