What chemical will remove the black deposits on the inside of fixer bottles? Please don't tell me it's nitric acid, l don't know where to buy that or even if they would sell it to me.
I do something similar to Gerald. I use household chlorine bleach, which will rehalogenate the metalic silver. After the stain has disappeared, rinse well and then use some regular fixer to dissolve the invisible deposit. Rinse again and you're good to go.