The company I work for has a pool in which someone added ph minus directly to the pool a few days after the plaster was done. There is a big white stain in the middle of this pool. We have been brushing the stain in addition to the normal brush down, but I'm wondering if there is anything else that can be done to fix this?
Would acid washing fix this type of stain? Would lowering the pH for a period of time have a similar effect?
I'm also interested in knowing what happens chemically between the sodium bisulfate and the plaster. Is the plaster dissolving, and then recrystallizing back onto the finish in those areas, or is the white stain a new compound?