Alternative Formulation For Pyrocat-HD Part B

[thronobulax]

The normal Part B for Pyrocat-HD is a 75% solution of Potassium Carbonate (750g/litre).

I am aware that a 20% solution of Sodium Carbonate can be used, but requires 5x the quantity Part B in that case.

I've seen reference to using 10% Sodium Hyroxide. Has anyone tried this and, if so, what does it do to the A:B mixing ratio?

Are there other Part B alternatives worth knowing about? The sodium hydroxide alternative is appealing because lye is relatively cheap as compared to Sodium Carbonate.

Thanks In Advance!

 

[Ian Grant]

When Sandy King formulated Pyrocat HD he used Sodium Carbonate for Part B, and it was I part A + 2 parts B.

Your 20% solution of Sodium Carbonate at 1+5 would be the equivalent to a 130% solution of Potassium Carbonate (at 1+1), which isn't possible. You need a 29% solution and use 2 parts instead of1 Part Potassium Carbonate

Sodium Hydroxide can be used but has a detrimental effect in softening emulsions.

Ian

 

[thronobulax]

What about borax as an alternative for Part B? Also would be interested if you have anything further on the effect of lye on emulsions.

I've got a pH meter on the way and I want to try to match the alkalinity of Part B by other means. I'd prefer to figure this out analytically by calculation, but that knowledge of chemistry has vanished with the years. So I will try by direct measurement.



(This is just an exercise in curiosity, there is not particularly important reason I am asking.)

 

[Ian Grant]

Borax isn't a strong enough alkali. Sodium Hydroxide severely softens some emulsions, and can cause if to frill and lift off the base. Sodium or Potassium Carbonate are cheap.

Ian

 

[thronobulax]

Interesting. I followed the suggestion of @Raghu Kuvempunagar earlier this summer of adding 0.5g/l lye to highly dilute D-23 and observed no emulsion issues, but I would imagine there is a point at which this gets overdone.

Thanks for the responses.

 

[Raghu Kuvempunagar]

What about borax as an alternative for Part B? Also would be interested if you have anything further on the effect of lye on emulsions.

You might be interested in this substitute that Peter Carter recommended for carbonate in Pyrocat. I tried it (1:1:100 dilution only) and it worked well. YMMV.