Does anyone know whether liquid concentrate of Potassium Citrate can be stored for prolonged periods of time? It is well known that dilute solutions of citrate will catch mold over time, but does this also apply to a 300 g/l concentrate? Would higher concentrations yield a stable liquid? Are there compounds which could be added, which would prevent mold growth yet not interfere with copper red toning? Would a mixture of Copper Sulfate and Potassium Citrate have decent shelf life?