I'm no expert but from what I've picked up along the way:
Doesn't look like a fogging developer going by the ingredients and the workflow in the screenshot (fogging dev would replace re-exposing step).
Hydroquinone works as a developing agent by itself at higher pH.
You're right GE, not fogging.
Now you've got me curious, I wonder if there is any real advantage to just using hydroquinone and not adding phenidone
Using hydroquinone alone creates higer contrast than the P-Q combination. This effect was also used in Kodak's D-8 super high contrast developer for direct positive film.
How does the boric acid come into the mix?
A borate buffer is interesting. I'd imagine the precision on the amount of boric acid would be fairly critical because of it and the pot bromide are the only inhibitors I see.It creates a borate buffer together with the hydroxide. Although given the ratio between the two, the pH must shift all the way to the upper end. Not sure if this is the only or main reason why it's in there, but I'd expect so.
PS: it helps if you quote text from their original source because it preserves context. E.g. the D-88 formula you got from here: https://www.photrio.com/forum/threads/kodak-direct-positive-developer.31512/ In this case, it gives essential information about the "fogging?" bit because it's mentioned as a developer for direct positive paper, and post #5 in the thread contains essential information on that aspect.
As to why hydroquinone on its own gives 'high contrast' (the question is what is exactly meant by that - high dmax or cutting off of shadow detail?) - I suspect you may have to refer to the literature and that the underlying chemistry might be complex. You could start in e.g. Mees; https://archive.org/details/TheTheoryOfThePhotographicProcess Chapter XI might give some clues.
The exact formula I used was a pinch different to that described on this website, but virtually the same.What was your source for D-88. It's obviously quite a high contrast developer.
Ian
It's closer to D-85 which is a Lith developer, the major difference is the use of Sodium Hydroxide instead of Paraformaldehyde, so veery high contrast without infectious Lith style development..
It appears that D-88 was for an applied use with Document, Recording, Photomechanical, films & paper, terms used by Ilford.
Ian
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