I've been doing this toning process off and on for over 10 years. While I was assisting, I learned this process where you take a BW print that printed darker than normal, then it's "toned" in a solution of potassium Ferricyanide and potassium bromide. The print is bleached to a certain point. I then wash the bleached print then re-expose it in bright sunlight. The image comes back a brownish. It looks sort of like a lith print. Is this a toning process? How toxic is the solution of potassium Ferricyanide and potassium bromide? Thanks in advance.