Gainer Pyrocat B

juan · Oct 29, 2021

Years ago, Pat Gainer was bothered by the reaction caused by mixing carbonates with his calcium filled water. I have the same problem. Gainer went to his dungeon and found a solution.

https://www.photrio.com/forum/threads/pyrocat-hd-solution-b.47890/reply?quote=695683

I tried to mix his part B substitute of 69g borax and 36g sodium hydroxide. I poured 800ml of distilled water into a beaker on my magnetic stirrer, then began to add borax as it is first on the list. At about half the borax, the mixture became pure of a suspension and by the time I added all the borax, there was a thick layer of solids on the bottom. I let the stirrer work for a half hour with no progress. I decided I couldn’t make a worse mess, so I added about half the sodium hydroxide. In a couple of minutes the solution cleared and all of the borax mixed. I added the rest of the hydroxide, and ended with a clear solution with no undissolved solids.

Should the hydroxide have been added first?

Donald Qualls · Oct 29, 2021

I doubt it makes a difference in this case -- you're converting (most of) the borax to metaborate by adding the hydroxide, and you'll get the same result if the hydroxide is already in solution when you add the borax.

One potential disadvantage: if you get interrupted after dissolving the lye, it will lose strength by reacting with atmospheric carbon dioxide. How rapidly that would happen in a 3.5% w/w solution I'm uncertain; it might be nothing to worry about.

To my eye, it's more interesting to watch the well oversaturated mixture clear up; something similar happens when mixing 1920s recipe Rodinal.

Alan Johnson · Oct 29, 2021

The solubility of sodium tetraborate decahydrate in water is only about 38g/L at 20C, Gainer may have warmed it up somewhat but simply adding sodium hydroxide provides considerable heat of solution ,probably adequate for the purpose.

Raghu Kuvempunagar · Oct 29, 2021

Does Metaborate work well as the accelerator in Pyrocat? Catechol supposedly forms a complex with borates and consequently looses most of its reducing power. I guess this phenomenon is pH dependent and the excess Sodium Hydroxide helped Gainer somehow. Peter Carter tried something similar and seemed to have got good results.

Alan Johnson · Oct 29, 2021

Raghu Kuvempunagar said:
Does Metaborate work well as the accelerator in Pyrocat? Catechol supposedly forms a complex with borates and consequently looses most of its reducing power. I guess this phenomenon is pH dependent and the excess Sodium Hydroxide helped Gainer somehow. Peter Carter tried something similar and seemed to have got good results.

Good spot, you are right, IIRC I got blank film with pyrocat and metaborate.

juan · Oct 29, 2021

I tried this solution with Pyrocat HD A solution and got what look to the naked eye like normally developed negatives. Certainly not blank.

Raghu Kuvempunagar · Oct 30, 2021

Metaborate does diminish the activity of Catechol - I've verified this several times. However, Gainer's concoction uses a good excess of Sodium Hydroxide along with Metaborate. One consequence of this is a significant increase in pH which not only raises activity of Catechol but could also be regulating the complex formation with Metaborate. Why not use just Sodium Hydroxide as the accelerator as it is known to work fine as per Sandy and others?

Anon Ymous · Oct 30, 2021

@juan I had exactly the same problem, which I solved by using sodium hexametaphosphate. I add a little bit of it in my tap water when I prepare my working solution and the problem is gone. I use deionised water for the carbonate solution, which I mix at 25%, 1/3 of the initial concentration. This takes care of crystallisation during storage at low temperatures, but I obviously have to use three times as much.

My pyrocat working solution would become a murky mess during use, resulting in numerous spots on the negatives.

Anon Ymous · Oct 30, 2021

Oh and in case you're wondering why I didn't use hexametaphosphate for the carbonate solution, it's because in long storage in alkaline solutions it tends to hydrolise (IIRC) and will likely not work from some point on.

juan · Oct 30, 2021

@Raghu Kuvempunagar - I don’t see any references to just sodium hydroxide as the B solution. Do you have an amount?

@Anon Ymous - Do you have an approximate amount for sodium hexametaphosphate? I usually mix working solution by adding dry sodium carbonate to 5 liters of tap water. I don’t usually mix up a B solution. I realize the hexametaphosphate is probably not a critical measurement, but I don’t know if a gram or a kg would be a starting point.

I’m clearly not a chemist. Just a mad scientist in the darkroom.

Anon Ymous · Oct 30, 2021

@juan As you said, it's not a critical measurement. AFAIK, it won't affect pH, it's more or less neutral unlike other agents, so a bit more won't matter. For 500ml of working solution, I just pick a bit at the tip of a plastic teaspoon I use to mix chemicals. If I were you, I'd experiment with 500ml of tap water, add a small, known amount of hexametaphosphate and add whatever carbonate needed for it. If it remains clear after some time, it means it's enough. From this, you can scale to whatever quantity you need and get an idea of its volume. IMHO scales are a bit of an overkill for this. Or maybe I'm too lazy.

juan · Oct 30, 2021

Thanks.

Raghu Kuvempunagar · Oct 30, 2021

"To make a working solution using 10% sodium hydroxide as Stock B dilute 1 Part Stock A + 1.5 Parts Stock B + 100 Parts Water. This working solution will give similar results to the regular 2:2:100 dilution using potassium carbonate."

https://unblinkingeye.com/Articles/PCat/PCat2/pcat2.html

Please do note the caveats that the above article makes in connection with Sodium Hydroxide.

juan · Oct 30, 2021

Forgot about that site. Thanks.

Gainer Pyrocat B

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