Cleaning and chemistry (gum bichromate)

[Aimee Danger]

It’s been a LONG time since I took chemistry so this question is for all the chemistry pros out there. I work in gum and cyanotype. I want to clean my dim room sink and countertops to avoid cross-contamination as much as possible. I realize I don’t know what happens when potassium/aluminum dichromate meets vinegar, bleach, sodium, etc.
1. Will any of these combinations produce something toxic? (sulphuric acid gas, for instance)
2. Will any of these produce cool effects? I used to take apart my Polaroids and spray them with saltwater while they were developing and have thought about trying the same here.

 

[Bronson Dugnutt]

Dichromate (Xy(Cr2O7)z) compounds contain the hexavalent form of chromium which you're aware, judging from your question, is hellishly toxic. Most photographic uses call for a sulfite clearing bath, one role of which is to reduce the hexavalent (+6) chromium to the trivalent (+3) form which is some measure less hazardous... but still a heavy metal. Wiping surfaces with a solution containing sulfite to ensure no bits of the hexavalent form are lingering would be one thing you could do presuming no one is allergic. Adding a mask/respirator to the usual kit of gloves and goggles and ventilation, especially when handling powders, wouldn't hurt.

1. Gas-evolving chemical reactions relevant to photographers are of the acid-base variety; knowing the pH of various solutions is key. When solutions of different pH are mixed, gases can be produced, depending on the reactants involved (e.g. developer & fixer). The most common hazardous gas generating reaction known to the layperson are combinations of household chemicals that can produce chloramine gas. AFAIK dichromate doesn't form any gaseous chromium compounds at standard temperature and pressure, but is often used in acidic conditions (bleach & hardening baths, for instance). Keep strong acids away from ferricyanide compounds.

Here's a quick anecdote I found on the topic and highlights a few best practices (like why using a stop bath is a good idea): https://www.apogeephoto.com/film-photography-is-your-darkroom-safe/

2. In your polaroid example the menagerie of salts in seawater would be altering the pH and halide characteristics of the developing film. Gum and cyanotype (iron salt) being 'print-out' rather than 'develop-out' processes lack that step to intervene but additional effects are achievable during printing or afterwards by toning, spotting, physical manipulation etc. Chemigrams and chemigram-like techniques are fun to explore if you're already comfortable with 'standard' alt process techniques.

 

[Aimee Danger]

Oh dear. Are you saying that the dichromate and the cyanotype chemicals could be reacting to each other? This is a pretty common combination.

 

[koraks]

Are you saying that the dichromate and the cyanotype chemicals could be reacting to each other?

Not really. It's not a big risk in any case if you're overlaying one on top of another in a print, for instance.
He's referring to the risk of mixing ferricyanide (from the cyanotype mix) with strong mineral acids (e.g. sulfuric acid) as this will liberate cyanide gas, which is deadly.

When cleaning, just don't go overboard. Firstly, cross contamination isn't as much of an issue as you may think with the kind of processes you're using. Basically a thorough rinse of surfaces would already be mostly sufficient to deal with this. Secondly, if you clean your stuff while the contamination is still fresh (i.e. not dried in yet), it's easy to remove.

There's no really valid reason to resort to agents such as bleach or vinegar to clean your workspace and utensils. Water and perhaps some soap will do, really.