Ferricyanide before Developer

newcan1 said:

Because the multigrade quality of the paper is dependent on dyes within the paper separating how the exposure affects two different layers within the paper. The water in the bleach will dissolve away those dyes.

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As I understand it, there are no multigrade layers in modern multigrade paper.
The two emulsion components are completely intermixed in the emulsion.
They actually don't differ in contrast - they differ in sensitivity. And it is the combination of the two or three different components that creates the ability to vary contrast.