As you know, Parodinal is the generic name for clones of the famous Agfa universal B&W developer Rodinal.
I tried a new formula and called it 645-Parodinal, because its recipe has following ingredients, for 500 ml of concentrate:
60 g Potassium Metabisulfite
40 g Paracetamol
50 g Sodium Hydroxide
First of all I transform the Paracetamol pills in powder with a pestle and mortar. I am not sure whether it is possible to jump this step and use directly the pills without all that work. But ok, next time I try it.
Then I use two 1L beakers, at least one must be heat-resistant. In both beakers I put about 180 ml of water, but in one of them warm water and in the other cold water. In the one with warm water I put the 60 g Metabisulfite and the 40 g Paracetamol and stir. It will not dissolve but never mind. In the other beaker I disolve 50 g of Sodium Hydroxide, it will become very hot. While hot I pour it on the other beaker, stir and complete with water to make 500 ml. The next I put the beaker with all the stuff in a warm bath at fire and stir for several minutes until I get an homogeneous soup, looking translucent. When finished, I switch off the stove and let the mixture cool down.
Finally I store the 645 in a 500 ml amber bottle well closed.
The last film I developed was a Shangai GP3 at box speed and I used the dilution 1:100 and 30 minutes. It could be less time, I think it respects Rodinal times, but I prefer the 'steak' well done.
Some recent photos of a 120 film exposed with a Topcon Horeseman 980, format 6x7 and developed with 645-Parodinal.