Solvents/inks that have been indicated as detrimental to photopolymer plate health and longevity are those containing acetates. Plate washes formulated specifically for photopolymer plates are best, but are increasingly hard to find. Most of the plate washes that I have used, such as Anchor's Aled, are no longer on the market. Like type washes, plate washes are fast drying to prevent the solvent from remaining in the relief of the plate and contaminating the ink film.
A particular concern with photopolymer plates is cleaning during a pressrun. Ink runoff and debris, such as paper dust and rag fiber, can accumulate in the relief area of photopolymer plates, which, unlike metal type or metal plates, is tacky and will retain these materials. They will attract further ink into the relief areas and eventually come into contact with the surface film, causing your imaging to become fuzzy or blurry. This aggregate of material is quite difficult to successfully remove. If your plate processor supplies proofs along with your plate, you may notice the relief is already contaminated with lint and residue ink from the cleaning process.
Some solutions: Inexpensive fast dryers like 100% Isopropyl Alcohol (printer’s alcohol) or Coleman Lantern Fuel (white gas) work well as substitute plate washes if used in moderation. Note: these are highly flammable and need special storage containers. There are special lint free tight-weave cloths on the market (medical, aerospace) that I suggest for cleaning plates. Combined with a soft toothbrush, such as those used for gum health, as well as a spray of compressed air, will help quite a bit in keeping the relief area clean.
In regard to storage, mainly keep the plates away from light and heat as well as ozone, the primary cause of plate deterioration. Ozone is generated by electrical motors, lighting, etc. It is also more common in the local atmosphere during the summer months. Combined with high temperatures it will deteriorate the plates quickly, and in severe conditions, cause cracking. It is not uncommon for polyester-backed plates with significant surface area to curl while in storage; there is very little that can be done about this as these are the result of natural stresses.
Used plates should be stored flat in paper envelopes, wrapped in Saran Wrap or black plastic, or sealed in Zip Lock bags (a temporary means to preserve plates is a breathe of air into the plastic bag before closing, ensuring that moisture and carbon dioxide are trapped with the plate). Carbon dioxide baths have been used to preserve and revive plates (in photopolymer's earlier years) and antiozonants (such as ArmorAll) have preservative qualities, but it is far better to regenerate from the original negatives than to re-use an older plate, as you cannot successfully halt the degenerative process (the printing qualities of a freshly made plate, its tack and resilience, wanes over time). Save your film negatives in envelopes with the emulsion side protected with acetate slips.
Copyright © 2009 by Gerald Lange
Photopolymer plate cleaning and plate longevity
