Re: cyanotype question
Maybe an unrelated question--is it **possible** that the bleeding in pt/pd could similarly be caused by an excess of iron?The explanation why an excess of "reactive iron" to "color-forming iron" (i.e. K ferri) produces bleeding would be that the reacted iron moves from its original position faster than the K ferri reacts with it.
So I second that this would apply also to other iron processes, substituting the "color-forming iron" whith whatever reacts with the photochemically formed iron(II). The calculation have to be made with moles and not grams. Note that am fe citrate is the only poorly defined substance (a 14.5-16% Fe).