February 8, 2013
neiromobile-blog asked: Hi, Tony! I really want to try gum bichromate printing, but I am very concerned about the toxicity of the main component — potassium dichromate. I do not have a separate room for the process at the moment. Can I do this at home? In the bathroom. What safety precautions when working with potassium dichromate?
There is a long tradition of bathroom darkrooms. When I first started with Gum over ten years ago, I used the tub in my bathroom for about a year or so making prints using 13×19 inch negatives in 16×20 inch trays. It wasn’t ideal but it worked-a lot of my preliminary research was done during that time. It’s important to have a healthy respect for the Dichromate (I use the Ammonium Dichromate). Wear a mask when dealing with the dry chemistry and wear gloves when handling the Dichromate (wet or dry). Fastidiousness is a necessity–make sure to clean all areas in contact with the sensitizer. Refer to the MSDS sheets for further handling precautions. Tony
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Hi Tony, long after the original post, but maybe useful for some: Harmful chrome-6 (which is yellow-orange), is reduced to harmless chrome-3 (which is green and insoluble) by sulphite. In event of a spill or splash (or regardless), clean the work station first with a wet-wipe moistened with sulphite solution and then again with clean water. That way you know that you won’t accidentally touch dichromate later and absorb it through the skin. The waste water from printing, rinsing coating equipment etc., one can accumulate and neutralize before discarding. This provides an avenue for safe and responsible home printing without a complicated effluent system.