Citric Acid Pickle
Weve used a citric acid pickle for about 9 months now with great results. Citric acid is a fairly common preservative used for canning foods (i.e. its edible). Citric acid is non-toxic, in fact its derived from citrus fruits, and its relatively cheap and easy to find. It works fine as an alternative to Sparex or other chemicals to remove flux (halide salts used to ease the flow of solder), oxides and firescale after soldering.
Citric acid is much less caustic and tends to last longer than other pickling agents. It can cause eye, skin, and respiratory irritation -so be careful, but weve never gotten any burns. The biggest drawbacks are that citric acid has to be heated (as opposed to Sparex, which just works better hot), and it takes at least twice the time to work. There is some debate over the ideal water/citric acid ratio, but we use about 10:1 water to citric acid with good results. Some jewelers say that distilled water works infinitely better than tap, but we havent had any issues. It may depend on the mineral make-up of your tap water. You can buy citric acid (the technical name is anhydrous fine granular citric acid) at wholesale prices from spice & herb or chemical companies, and sometimes at the grocery store with canning supplies.
To dispose of citric acid pickle: neutralize it first with baking soda, and check with local waste management authorities for regulations (down the drain? cat litter?).
This site has art materials disposal info:
Citric Acid material safety data sheet:
More comprehensive Citric Acid Pickle article: