Just returned to a bottle of Ammonium Citrate developer that's been sitting ... for a while. There appeared to be mould in the bottom of the bottle ... which filtered out easily with my usual high tech coffee filters. Have googled around the problem, without much luck ... just wondering if there was anything I could add or do to prevent this happening again?
I have not seen it personally, but have read of it happening. I am not sure, but storing it in the freezer may dissuade mould growth.
Be sure to let fully warm before openning the bottle, so as to avoid condensation issues.
In one of the alternative photography technique books - I can't remember which one - it does say that mould is fond of growing in the Ammonium Citrate solution. It certainly does in mine. The book says this is normal - just filter it through gauze or a filter paper . I've done this many times and it seems to do no harm.
Various molds and bacteria find citric acid and its salts to be very tasty. Keep the solution in the refrigerator. As a general principle do not freeze solutions. Some chemicals once they crystalize out may be very hard to get back into solution. However,I don't think that this would be a problem with ammonium citrate.
To solve the mould issue on Ferric Ammonium Citrate for cyanotype, I add about 2ml of Listerene mouthwash to each 100ml of solution. There is no effect on cyanotype printing but I do not know how it would interact in your situation.