Addressing the ‘safe’, ‘eco-friendly’ and ‘water wash’ myth in flexographic and solar plate-type printmaking
During processing Photopolymer Printing Plates may emit: Vinyl chloride gas / styrene gas / phosgene gas / benzene / …
DANGER: This method is suspected to involve undeclared and poorly detectable harmful and carcinogenic emissions! Artists are advised to not use this process without adequate protective measures.
For about twenty years there have been recurring anecdotal suggestions from regular users of photopolymer printing plates (Flexo / Solarplate / Letterpress Photo-polymer Plates with a hard metal or polyester base) who believe they may have contracted cancer — even brain cancer — from this common plate making process that is popular and widespread in artist’s intaglio and letterpress printmaking, and in the printed packing flexographic industry.
Despite the anecdotal hazard and sickness reports there was little published information about possible exposure mechanisms that could be a likely cause, and the process seems at first glance ‘waterbased’, ‘water-washable’, and of low hazard. But there were early warning signs: Significantly, the flexographic printing industry has long had significant numbers of law suites related to cancer in workers working in flexographic plate making; with vinyl chloride and asbestos poisoning as a likely cause; and some law firms specialize in that area.
NOTE: the dry photopolymer films from the circuit board and IT industry differ greatly from photopolymer plates; the polymer chemistry of dry film is more modern (it is not PVC based, but acrylates based) and has better safety credentials than flexographic plates
Product literature for photopolymer printing plates makes little reference to such hazards, and instead suggests user friendliness because of the ‘water wash’ processing method. In polymer plates artists are using an industrial product that is designed for fully enclosed machine processing (known as closed circuit polymerization) with appropriate extraction systems in the packaging and printing industries.
Professional industrial facilities that process these PVC / Nylon type polymers in the rubber, tire and printing industries have long avoided open tray ‘hand processing’ that involves VOC emissions, and replaced it with fully automated machine processing which is essential for safety. Polymerization chemistry is kept away from the workers.
We strongly advise artists against the regular use of hand processing of any type of photopolymer (flexo-type) plates, unless a full organic respirator and ventilation are consistently employed during all steps of this particularly hazardous and insidious process, which may seem quite safe when it probably isn’t safe at all!
a photopolymer plate processing machine. the ‘treatment’ section needs to be connected to a fume extraction system that vents to the outside.
Print shops and institutions are strongly advised to purchase professional, fully enclosed, and automated plate processing machines with full extraction systems in order to ensure a safe plate making processes.
In studio tests we found evidence that water wash photopolymer plates may emit significant amounts of VOCs or SVOCs, (semi volatile compounds such as vinyl chloride) mainly during the final ‘scrubbing’ phase once the plate is in contact with air, following the tray development in water. These fumes are hard to detect but may have a sweet smell which indicates the presence of airborne vinyl chloride or styrene monomer, both of which are known and powerful carcinogens.
This may be the exposure mechanism at play: Heavy and semi volatile fumes can concentrate above the plate surface during scrubbing and rinsing, exposing artists to significant amounts of toxins without ever noticing it. Unknowingly, regular users of this popular photo-intaglio plate making process may expose themselves to invisible and cumulative hazardous emissions that may increase the likelihood of ill health or cancers after a few years of working with this method.
Although flexo plate manufacturers do not typically disclose the patented composition of their resins or their plates, — and do not list emissions in ssd sheets — it is widely known that some key monomeric components of flexographic plates (from various manufacturers) may be polyvinyl chloride (PVC), and sometimes Nylon, in combination with a small amount of acrylates (for instance MMA or Ethyl Acrylate).
Styrene-butadiene-styrene (SBS) block copolymers are commonly used as a primary binder or a component in the resin formulations for some types of photopolymer flexo printing plates.
SBS is a thermoplastic elastomer that provides the necessary flexibility, elasticity, and mechanical properties required for a flexographic printing plate. The complete photopolymerizable composition typically also includes ethylenically unsaturated monomers, a plasticizer, and a photoinitiator.
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Other types of resin chemistry can include:
• Styrene-isoprene-styrene (SIS) block copolymers
• Copolymers of butadiene and acrylonitrile
• Acrylated polyurethanes & nbspNOTE: 1,3-Butadiene: Known carcinogen (EPA) and probable human carcinogen (IARC Group 2A). Exposure linked to leukemia, reproductive/developmental issues in animals, and respiratory irritation.
essentially, flexographic plates and processes typically entail similar toxic hazards and occupational sickness profiles as are common in the car tire industries and synthetic rubber manufacturing
Rubber Printing Plates may be composed of up to 50% PVC
The PVC content in these plates may be at a percentage of up to 50% to provide flexibility as well durability of the UV sensitive printing plate (quoted from: Sun Chemical).
Treatment of Washing Water: Photopolymer Plate Making produces large amounts of monomeric plastics, heavy metals, and solvents that enter the washing out water during processing. Do not discard this effluent down the drain, but use a flocculation method to break down this sludge into safe components that can be discarded. See page: