Pyrocat HD recipe help!!

[Donsta]

I've been doing a whole lot of testing with Pyrocat HD in a Jobo processor. I've just noticed, while mixing up the latest batch of chemistry (which I purchase from Photographer's Formulary) that there appears to be some discrepancy with the actual make up of the part B solution - all of the original publishing of the formaula I can source suggest that the Part B solution is now a 100% solution of Potassium Carbonate - from what little I know, this implies mixing 100 grams with water to make up 100ml of the solution (i.e. water to make up 100ml - not 100ml of water - in fact somewhat less). I've just had another good look inside my PF box and while everything else seems to agree with the publishes formula, the PF kit contains a bag which is in fact labelled 100grams. Of course, the instructions imply mixing 75g with water to make up 100ml of solution (which doesn't agree with what I though on a 100% solution). As it turns out, I have been mixing this bag up as though it was in fact a 75g bag as detailed in the scant instructions. The long and the short of this is that I am having a dreadful time with excessive B+F with Efke 100 in Pyrocat HD on my Jobo - could this "super concentrated" Part B be the problem? Or is this 100gram bag (it weighs out at about 100 grams, so that's not a typo) the correct amount to make up a 100% solution when mixed with water to make 100ml of solution?

Secondly, hope should I be mixing up this 100g bag to make the correct solution for B?

 

[sanking]

I've been doing a whole lot of testing with Pyrocat HD in a Jobo processor. I've just noticed, while mixing up the latest batch of chemistry (which I purchase from Photographer's Formulary) that there appears to be some discrepancy with the actual make up of the part B solution - all of the original publishing of the formaula I can source suggest that the Part B solution is now a 100% solution of Potassium Carbonate - from what little I know, this implies mixing 100 grams with water to make up 100ml of the solution (i.e. water to make up 100ml - not 100ml of water - in fact somewhat less). I've just had another good look inside my PF box and while everything else seems to agree with the publishes formula, the PF kit contains a bag which is in fact labelled 100grams. Of course, the instructions imply mixing 75g with water to make up 100ml of solution (which doesn't agree with what I though on a 100% solution). As it turns out, I have been mixing this bag up as though it was in fact a 75g bag as detailed in the scant instructions. The long and the short of this is that I am having a dreadful time with excessive B+F with Efke 100 in Pyrocat HD on my Jobo - could this "super concentrated" Part B be the problem? Or is this 100gram bag (it weighs out at about 100 grams, so that's not a typo) the correct amount to make up a 100% solution when mixed with water to make 100ml of solution?

Secondly, hope should I be mixing up this 100g bag to make the correct solution for B?

The original Pyrocat-HD formula called for mixing 100g of potassium carbonate with 100ml of water. When mixed that made a total of about 135ml of total solution, or about a 75% solution. That wording apparently confused some people so I changed the formula so that it now states mix 75 grams of potassium carbonate with water for a total of 100ml of solution. This also makes a 75% wpv solution.

My understanding is that the present liquid kits distributed by Formulary have a Stock B solution that is a 75% wpv solution. I don't know about the kit that comes in powder, but you can easily weigh it yourself for verification.

If you were to mix 100 grams with water to make a total of 100ml of solution, which is possible because of the solubility of potassium carbonate, you would have a slighter stronger Stock B than specified. It would be something like changing the 1:1:100 dilution to 1:1.25:100. That might cause a little extra general stain, but not as much as you are apparently experiencing with Efke PL 100.

Sandy

 

[Donsta]

Thanks Sandy - I will battle on with this. I think the next step must be to send some tests off to someone with a UV densitometer to get some actual numbers...