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Robert Langham
7-Sep-2015, 15:56
I've been working through an order of Pyrocat HD in Glycol. It's a wonderful developer, as many folks say. I noticed that my solution B bottle has precipitated out some kind of solid. When the bottle is shaken, it sounds like plastic pellets in the bottom. I didn't notice it until recently, (though I wasn't shaking the bottles before drawing the solution for use.) Doesn't seem to have effected the performance of the developer.

Anyone got an idea? I rather like this developer for HP5 Sheet film. I'd been using Xtol, which I liked a lot but I think I prefer the Pyrocat.

Thanks.

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sanking
7-Sep-2015, 18:24
Sounds like some of the potassium carbonate fell out of solution due to low temperature. Place the bottle of Solution B in a warm water bath for a couple of hours and carbonate should go back into solution.

Sandy

Robert Langham
8-Sep-2015, 07:05
Sounds like a simple fix. Thanks!

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Harold_4074
8-Sep-2015, 15:15
I would suggest redissolving the salts only if the bottle is nearly full. Crystallization occurred because the solution was close to saturation to begin with; if you have used a substantial amount of the Solution B, you have removed proportionately more water than carbonate (or whatever the salt is). Warming up the remaining solution may allow you to redissolve everything, but you will now be using a more concentrated solution than you did originally, and I don't know how sensitve Pyrocat is to alkali concentration. It will also drop out again if the temperature decreases.

I have the same issue with PMK, but I realized that if the darkroom stayed at approximately constant temperature, the saturated solution (with excess at the bottom of the bottle) would give consistent results anyway.

sanking
8-Sep-2015, 19:28
Correct, if a large percentage of Stock Solution B has already been used then warming the solution to redissolve the potassium carbonate will result in a slightly more concentrated solution. However, the original solution is so concentrated it probably won't make any difference in the working solution. The Stock B solution is a near saturated solution of potassium carbonate, and contains 750 grams of the chemical in one liter of stock solution. Yes, that is 750 grams of potassium carbonate in one liter!! I doubt that more than 5-10 grams of the chemical has dropped out of solution so warming it is not going to have much real impact on the working pH given the buffering ability of the carbonate at this concentration.

Sandy



"Crystallization occurred because the solution was close to saturation to begin with; if you have used a substantial amount of the Solution B, you have removed proportionately more water than carbonate (or whatever the salt is). Warming up the remaining solution may allow you to redissolve everything, but you will now be using a more concentrated solution than you did originally, and I don't know how sensitve Pyrocat is to alkali concentration. It will also drop out again if the temperature decreases."

Robert Langham
17-Sep-2015, 13:17
A little hot water and agitation drove it back into solution. Sounds like it will be fine but if there is any change it's a quick fix to order more. Next bottles I'll watch closer and follow the directions to shake it. Going to test some FP4 in it to be ready for shadowed wall shapes in Canyon de Chelly. Need a little more contrast than I was getting with HP5.

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HMG
5-Mar-2017, 11:26
I have a similar situation. I was given some PMK, via an intermediary, from an experienced photographer who said it was good. There's a 1L bottle of solution B that is about 90% full and has what I estimate as about 1/8 to 1/4 cup of crystals in the bottom. Many of the crystals are large flakes, about 3/16" x 1/2".

Soaking for a few hours in hot water (with a couple of water changes to keep hot and periodic agitation) has not had a noticeable effect on the volume of crystals. As I shake, I see a lot of tiny grains, I assume the same precipitate.

Obviously I can try using it but, before I do, I thought I'd seek the collective knowledge of the forum:
- Is there another way to force it back into solution?
- If not, is this volume of precipitate likely to effect usage? I assume I should filter it out.

Thanks.

Peter Gomena
5-Mar-2017, 12:35
I think PMK uses a "kodalk" accelerator solution (I think it's sodium metaborate), not sure what the trick is to get it back into solution. Warm it and shake it for a while and see what happens. Pyrocat-HD solution B goes back into solution pretty readily, but it's a different animal than the PMK solution B.

HMG
5-Mar-2017, 13:25
I think PMK uses a "kodalk" accelerator solution (I think it's sodium metaborate), not sure what the trick is to get it back into solution. Warm it and shake it for a while and see what happens. Pyrocat-HD solution B goes back into solution pretty readily, but it's a different animal than the PMK solution B.

You are correct about the Kodalk. "Kodalk" is also on the handwritten solution B label. I should have mentioned that in my initial post.

esearing
5-Mar-2017, 17:47
Is there a temperature range Pyrocat HD in glycol should be kept at? My darkroom is in my garage and can go from 40 to 80 degrees over the course of a year.

Fr. Mark
5-Mar-2017, 17:58
The Sodium Carbonate solution (which cannot be made as concentrated and subsequently you use more to get to the same alkalinity) also tends to have the carbonate grow Xtls in the bottom of the bottle. It is also v. close to saturation and gets hot enough when mixing it, that it may be beyond it initially v. the r.t. solution? Any way, it seems to work fine even with Xtls in the bottle. One way around the question of concentration might be to make the solution B saturated on purpose in the first place so there's always Xtls in the bottom of the bottle...then so long as you don't have major temperature swings (a challenge with basements, too, btw, in some parts of the world) the concentration is "guaranteed" to be constant. Then just tweak your development if you can tell any change from the "standard" concentration. Meanwhile, mainly listen to Sandy not me, he developed the stuff, iirc. Someone said "order more"? I know you can, but why not mix it from powders? way less costly to ship.

Barry Wilkinson
6-Mar-2017, 01:35
I read elsewhere here that some mix solution B with half the amount of Sodium Carbonate so it is not so saturated. When making up a working solution they use 1:2:100 instead of 1:1:100. I have not tried this, would you still get precipitation?

Doremus Scudder
6-Mar-2017, 02:31
With PMK, solution B is a saturated solution of sodium metaborate. It should be mixed with distilled water. If not, and the tap water has lots of minerals in it, you'll precipitate a lot of the metaborate out. I suspect it forms compounds with the other components in the water. This precipitate may not go back into solution (I think it may end up being insoluble). If a lot of metaborate has precipitated out, it can affect the activity of the developer. I did this once and compensated by adding more of the affected solution B. I was lucky enough to have a good solution B on hand to compare to. If you don't, you may simply want to mix new solution B with distilled water and use that. The solution A will still be good enough.

Another approach would be to filter out the precipitate and try to dissolve it separately in distilled water. If successful, you can add the two volumes together and simply calculate how much more of the new, weaker solution B you will need to get the right amount of metaborate in the final developer. If it doesn't dissolve, then you're back to square one; use more of the affected sol. B or mix new.

If, however, you just have a few particles rolling around in the bottom of the bottle, and you're sure you mixed it with distilled water in the first place, your solution is likely just fine. The particles are impurities or extra metaborate; the amount in solution is probably well within working tolerances.

Best,

Doremus

j.e.simmons
6-Mar-2017, 04:40
I've found it easier and more reliable to compute the amount of carbonate or metaborate that is in the WORKING solution, then add that amount of dry chemical to the diluting water then add the A. For instance, for a gallon tank I add a gallon of water then 40g (I think - I don't have my list here) of carbonate and stir. Then I pour in the A solution. That way I don't have to mix a separate B solution and risk it having problems.

sanking
6-Mar-2017, 15:09
I read elsewhere here that some mix solution B with half the amount of Sodium Carbonate so it is not so saturated. When making up a working solution they use 1:2:100 instead of 1:1:100. I have not tried this, would you still get precipitation?


Sodium carbonate works fine in Pyrocat but is much less soluble in solution. Since the Stock Solution B of Pyrocat is roughly a 75% solution of potassium carbonate, you could get an equivalent working energy of sodium carbonate mixed as a 20% solution with a 1 Part A + 4 Parts B + 100 parts water as with a 1+1+100 dilution using potassium carbonate.

The problem is that you would have even an even greater problem in keeping the 20% sodium carbonate in solution than you would with the 75% solution of potassium carbonate. This assumes that the No. 1 reason the carbonates go out of solution is due to drop of temperature in the storage area.

Consider that the solubility of sodium carbonate is only 12% at 10 C, versus 22% at 20 C, whereas the solubility of potassium carbonate is close to 100% at both 10 C and 20 C.

So from the perspective of solubility a saturated solution of potassium carbonate is much more stable across a range of temperatures from 20 and lower than sodium carbonate. And that is the reason I chose it for the Pyrocat formula over the more common sodium form.

My recommendation for storage of the Pyrocat Stock B is, every month or so check the condition of the solutions, and if any of the carbonate has fallen out of solution warm up the solution to 20 C or more. And be aware that the reason it falls out of solution is because the temperature dropped below what is needed to keep it in solution, below 10 C in the case of potassium carbonate. But it can not get out of the bottle, so just warm it up and it should work fine. Unless of course you allowed the stock to fall out of solution early on and have been using the weaker solution on top for a long time. In that case the easiest solution is to just add water at about 20 until the carbonate goes into solution.




Sandy

Fr. Mark
6-Mar-2017, 21:22
Great answer Sandy. It's amazing the difference a counter ion makes for solubility characteristics. Fwiw I have used Sodium Carbonate because I can buy it at the grocery store. No "chemical" mark up nor shipping cost.

Barry Wilkinson
7-Mar-2017, 01:38
Thank you Sandy.

Doremus Scudder
7-Mar-2017, 02:59
I've found it easier and more reliable to compute the amount of carbonate or metaborate that is in the WORKING solution, then add that amount of dry chemical to the diluting water then add the A. For instance, for a gallon tank I add a gallon of water then 40g (I think - I don't have my list here) of carbonate and stir. Then I pour in the A solution. That way I don't have to mix a separate B solution and risk it having problems.

This, of course, works just fine and solves the problem of the chemical precipitating out of sol. B. If you have a good scales and the dry chemicals stored (I'd likely use sodium carbonate for the Pyrocat), then you don't have to worry about storage temperature, distilled water, etc. Solution A for both Pyrocat and PMK does not have the precipitate problem.

Best,

Doremus

HMG
7-Mar-2017, 07:50
... Another approach would be to filter out the precipitate and try to dissolve it separately in distilled water. If successful, you can add the two volumes together and simply calculate how much more of the new, weaker solution B you will need to get the right amount of metaborate in the final developer. If it doesn't dissolve, then you're back to square one; use more of the affected sol. B or mix new.

If, however, you just have a few particles rolling around in the bottom of the bottle, and you're sure you mixed it with distilled water in the first place, your solution is likely just fine. The particles are impurities or extra metaborate; the amount in solution is probably well within working tolerances.

Best,

Doremus

Given that heat and agitation did not work, I'll strain out the precipitate and give the developer a try as is. I'll also grind up the particles and see if I can drive them back up into solution and how much distilled water that requires.

Based on a bit of research, it's my understanding that if my solution b is too dilute (from the loss of sodium metaborate) it won't be alkaline enough and the developer action will be inhibited. I assume that means overly thin negatives. I'll use a "known good" camera and meter, and shoot an easily metered scene.

Unfortunately, if my negatives are thin, I won't know for sure if the cause is dilute Kodalk or degradation of solution A. But some things in life are destined to remain mysteries.