Donald, just curious about whether you still use Parodinal, and if so, whether its grain properties differ from straight Rodinal. Second, is it possible to make Parodinal by adding tylenol to regular Rodinal?
Edit: Nevermind. After more reading, I now see that the tylenol is not an added ingredient, but a different way to produce the original formula. Chemistry was not one of my better subjects back in the day.
I've never used commercial Rodinal(-alike). I tried Parodinal after finding a formula for it and realizing I had everything on hand, and it was really, really cheap.
That said, from posted images I've seen, Prodinal works exactly like Rodinal -- same times at the same dilutions for the same film stocks -- and produces effectively identical negatives. Some of the more serious sensitometry practitioners might find it needs a small adjustment of time to give the same Contrast Index, but if so, it's a very small adjustment -- likely one 500 mg tablet more or less of acetaminophen/paracetamol in a liter batch of concentrate, or a gram or two more or less potassium bromide restrainer.
But yes, the mixing order (Tylenol first, then lye, then sulfite) very rapidly converts the n-acetyl p-aminophenol that is acetaminophen/paracetamol into plain p-aminophenol in solution (the high alkalinity cleaves the acetyl group off the main molecule, according to the actual chemists). If you mix in this order, and wait until the solution starts to turn pink before adding the sulfite, you can use the developer as soon as the concentrate is cooled to room temperature; if you add the sulfite before the lye, you'll have to wait 24-72 hours for the pink color that indicates enough of the pain releiver has converted to developing agent before use.
And, like "genuine" Rodinal, Parodinal will work at least until it's as dark as cola or coffee.
