Pyrocat Part B

Wayne · Nov 13, 2015

Well its more of Hydrocat-HD Part B because I'm using HQ not pyrocatechol, but I am using the sodium carbonate version of Part B. I mixed it up a few weeks ago and even used it several times, but when I went to use it last night there was a big chunk of carbonate in the bottom that I could not redissolve. I have not tried heating it yet, I just grabbed some Rodinal instead. So I'm just wondering wtf...it was dissolved when I mixed it. Temps in my darkroom can dip into the 50s or even 40 when I'm not using it, could that have precipitated it?

Ian Grant · Nov 13, 2015

It will redissolve, use gentle heat, put the bottle/container in warm water, gradually increase the temperature, shake as often as you can, eventually it will dissolve.

It would be better to make a more dilute version of part B, half the strength and use twice as much. Sodium Carbonate has tendency to crystallise out at lower temperatures. I have a jar of saturated Sodium Carbonate and it does solidify at the bottom, I can always get it to redissove, I use it to clean things.

Ian

Wayne · Nov 13, 2015

Thanks.

juan · Nov 13, 2015

Compute the amount of sodium carbonate in your final dilution, then just add that much dry chemical to the water, then add part A. I don't bother mixing a Part B.
juan

Wayne · Nov 13, 2015

That would work too. But once its mixed its always ready to go.

I heated it up and redissolved it tonight.

Rudeofus · Nov 15, 2015

Sodium Bicarbonate can form with Sodium Carbonate and aerial Carbon Dioxide, and it is much less soluble than Sodium Carbonate. Maybe this precipitate does not disappear with heating&stirring, but does go away after you add Sodium Hydroxide.

Anon Ymous · Nov 15, 2015

Once the precipitate is redissolved, then you can measure a volume of the part B solution and add to that the same volume of water. This will ensure that you won't have precipitate again at the same temperatures, but you'll have to use double the volume of part B.

Rudeofus · Nov 15, 2015

Anon Ymous, if the precipitate is indeed Sodium Bicarbonate, pH would be significantly lowered even if you get to redissolve it with enough extra water. In this case addition of lye is the only way to restore functionality of bath B.

Ian Grant · Nov 15, 2015

It's most likely still Carbonate and highly unlikely to have become Bicarbonate.

Ian

Wayne · Nov 15, 2015

It went away with heating and stirring

Pyrocat Part B

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