Alternative for bichromate in Gum-Printing?!?

Discussion in 'Black and White' started by martin_pistor, Nov 14, 2004.

  1. Hi folks,
    in trying to make first steps in gum bichromate printing I came to
    the problem, that here in Europe restrictions for purchase of
    hazardous chemical substances has been drastically enhanced appr. 18
    months ago. Obviously ammonium or potassium bichromate are classified
    as such (explosive, highly toxic, and cancerogen).
    Standing at the decision to learn about a process that might will be
    increasingly suffer from ressources and also problems in disposal of
    contamined waste (water)(besides health risks wich might be solvable
    with cautios handling of the substances) I'd like to know if there
    where any alternative (less hazardous) sensitizers discovered for gum
    Does the Photographers Formulary Kit contain the common receipe with
    25% ammonium bichromate solution?
    Still the idea of free choice of pigments is highly interesting to
    me, so any hint is welcome.
  2. Martin - gum printing is based upon the principle that dichromates(bichromates) affect the solubility of organic colloids like gum when exposed to light. The most common dichromates are the ammonium, sodium, and potassium salts, and all dichromates are oxidizing agents, which make them hazardous substances. Any kit for gum printing will contain one of these dichromates.
  3. Hi Dwane,
    thats what I understood. Just wondering if after more then 100 years of printing there where any other UV or light sensitive substance practically used besides silverhalides, dichromates and ferriccyanide (as I understood also platinum uses the ferric effect for primary sensitivity, then the platinum or palladium is reduced by the iron).
  4. Hello to you Martin. I guess we have this topic to ourselves - kinda of like being in a public chat room!

    In regards to other UV sensitive materials - as you have mentioned, the most common materials used have been silver halides, iron (ferric) salts, and the dichromates. I know that copper and uranium salts were once used in alternative processes, and I'm sure you can find information on the internet about this.

    If you are concerned about an alternative process that involves NO harmful chemicals, consider the anthotype process. It uses crushed flowers and water. Check for details on the process. This is an excellent source for information about alternative processes. You might also want to look at bromoil and carbon processes, which use ordinary photographic paper as a starting point.

    Hope this helps.
  5. Even bromoil requires dichromates in the bleach. There is no way around the use of hazardous chemicals, but there are plenty of folks who have handled them safely for many years.

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