Mixing Pyrocat-HD and Propylene Glycol

Lyn Arnold · Aug 30, 2007

I've been through many threads with keywords identical to the title of this thread, but can't find the answer to my question. I just want to mix Pyrocat-HD with glycol instead of distilled water in order to prolong the life of Stock Solution A. Sandy King suggested warming the glycol when mixing one of the Pyrocat formulae but it wasn't Pyrocat-HD. So...my question: what is the procedure for mixing Pyrocat-HD with Propylene Glycol?

Thanks in advance,
Lyn Arnold

Bruce Osgood · Aug 30, 2007

The following was taken from a thread and I don't remember who the author is. My memory is either Gerald Kotch or more probably PE or Sandy King. I'm sorry I cannot give credit to the author.

MIXING STOCK SOLUTION A WITH GLYCOL

As many of you know, mixing Stock Solution A of Pyrocat-HD in Propylene Glycol provides stability of the stock solution on the order of years, similar to HC-110. Here is a very safe way to do this, measured for the 1000ml kit.

1. Weigh out all of the chemicals for Stock A. 50.0g of pyrocatechin, 10.0g of sodium metabisulfite, 2.0g of phenidone and 1.0g of potassium bromide.

2. Pre-heat in a water bath or hot plate stirrer 750ml of propylene glycol to about 150F.

3. Add the pyrocatechin to the glycol and stir until dissolved. Should take no more than about a minute.

4. Now add the phenidone and stir. Should dissolve completely in about a minute.

5. Add the bromide and sodium metabisulfite to about 50-75ml of hot water at about 120F. Stir until completely dissolved, then mix with the propylene glycol solution.

6. Top off the solution with glycol to 1000ml.

Once you do this a couple of times you will find it just as easy as mixing Stock A in water. Should you be concerned about the small amount of water in the solution? Absolutely not. Pat Gainer, who is the expert on these type of solutions, has recently recommended this type of mixing for his PC-TEA formula, and if he is satisfied with the stability so am I.

juan · Aug 30, 2007

I heat mine in a microwave, but be careful - sometimes there's water in the glycol and it will steam off. I just heat the glycol and let it stand for a couple of minutes before stirring in the chemicals.
juan

gainer · Aug 30, 2007

Personally, I would use a small amount, say 5 grams, of ascorbic acid in place of the bisulfite and add bromide, if needed, to the the working solution. You may find the bromide is not needed.

Phenidone and ascorbate without sulfite form an active developer which IMO forms silver nuclei that act as catalyst for the pyrocatechin. This same reasoning seems to work for Pyrocat MC. In this case there is no H2SO4 to detach from the phenidone. There is also a Pyrocat PC that uses p-aminophenol base with ascorbic acid as the stimulant for the pyrocatechin.

Will S · Aug 30, 2007

photoformulary.com sells it pre-mixed in glycol. I just got some and have been happy with the results.

Thanks,

Will

Photo Engineer · Aug 30, 2007

I did not post the above but I can comment.

PG is flammable and the flash point is 99 deg C. The vapor is heavier than air. Therefore, you run the risk of a flame if heating near the boiling point of water especially over an open flame.

PE

sanking · Aug 30, 2007

Just for the record, I am the author of the directions Bruce posted for mixing Pyrocat-HD in glycol.

Sandy King

gainer · Aug 30, 2007

Photo Engineer said:
I did not post the above but I can comment.

PG is flammable and the flash point is 99 deg C. The vapor is heavier than air. Therefore, you run the risk of a flame if heating near the boiling point of water especially over an open flame.

PE

Here is the definition of flashpoint I found in Wikipedia:
"The flash point of a flammable liquid is the lowest temperature at which it can form an ignitable mixture in air. At this temperature the vapor may cease to burn when the source of ignition is removed. A slightly higher temperature, the fire point, is defined as the temperature at which the vapor continues to burn after being ignited. Neither of these parameters are related to the temperatures of the ignition source or of the burning liquid, which are much higher. The flash point is often used as one descriptive characteristic of liquid fuel, but it is also used to describe liquids that are not used intentionally as fuels."

The open flame can be beneath the container of Propylene glycol and it will not ignite at its flashpoint. The vapors have dispersed too much by the time they reach the flame. The autoignition temperature of propylene glycol is very, very much higher than any that we need to use. If you are leary of using a microwave oven, use a water bath. Any vapor that overflows from the glycol container will wind up in the water bath.

Lyn Arnold · Aug 30, 2007

Thank you one and all. You are a wonderful resource to tap in to.

Lyn

Photo Engineer · Aug 30, 2007

gainer said:
The open flame can be beneath the container of Propylene glycol and it will not ignite at its flashpoint. The vapors have dispersed too much by the time they reach the flame. The autoignition temperature of propylene glycol is very, very much higher than any that we need to use. If you are leary of using a microwave oven, use a water bath. Any vapor that overflows from the glycol container will wind up in the water bath.

Patrick;

This is correct.

The post above indicated use of a stirring hot plate, and some advocate heating on a stove with an open flame, so I commented.

I strongly advise that no one try to heat or warm PG on an open flame or on a hot plate where the heat source can be considerably higher than the liquid being heated.

PG vapor is heavier than air. A flash fire can take place which can be very damaging to anyone or anything within several feet, even if the fire extinguishes itself rapidly. I have seen this happen and had it happen to me. Lab accidents do happen.

PE

sanking · Aug 30, 2007

Photo Engineer said:
The post above indicated use of a stirring hot plate, and some advocate heating on a stove with an open flame, so I commented.

PE

Actually not. I only mentioned use of a stirrer hot plate, which does not involve an open flame. I also mentioned warming up the glycol in a water bath. I said nothing about using an open flame, and never have.

Sandy King

gainer · Aug 31, 2007

I know better after 80 years of near escapes from this that and the other than to say that any bad thing cannot happen. Edsel Murphy's law has been demonstrated over and over. A spill when moving a container of anything flammable from a heat source can be a serious event. In that way, the microwave may be the least hazardous, because it shuts off when it is opened. Cooking French fries is a hazardous endeavor. My grandmother was lucky she had left the kitchen before the can of beans she had put in the oven without puncturing it covered the kitchen walls with Campbell's Pork and Beans. This was long before the invention of the microwave oven. Anyone who puts a can of beans in a microwave is due for some fireworks, I expect.

Philippe-Georges · Aug 31, 2007

At the risk to be off topic, but while you all (Sandy, Patrick and PE) are on (in?) this threat, I would like to ask for your advice, if you do not mind off course.
A wile ago, I mixed up the 'Warm Tone Pyro Developer for Paper (1947)' formula as posted by Kino here on APUG (10-29-06).
The prescription said to use, among others, 22 grams op 'PYRO', as I did not knew what was intended, I used what I had : Pyrocatechine.
The developer did NOT work, not after doubling the exposure nor after doubling up the dilution.
So, just to be sure, did I had to use Pyrogalol instead of Pyrocat?

Thank you in advance,

Philippe

P.S. Sandy King's Pyrocat-HD is a 'heavenly revelation' to me, and I wonder if this could be used to develop paper....

john_s · Aug 31, 2007

leicam5 said:
...........
So, just to be sure, did I had to use Pyrogalol instead of Pyrocat?
....

Until recently, in all of the literature that I've read, "pyro" has always meant pyrogallol. I think that pyro can develop in less alkaline environments than pyrocatechol, so the pyrocatechol that you used was inactive. Adding some carbonate probably would have activated it.

bogeyes · Aug 31, 2007

crystals in dev

I mixed some pyrocat hd as described in this thread (heated in an old microwave) When the developer has been left standing for a while it forms small clear crystals in it. However once the dev is re-heated the crystals disapear. I have been using the dev for almost a year now and it still works as good as when it was first mixed despite all the repeated heating and cooling of the stock A solution (heated to about 52c and stirred to get rid of the mysterious crystals). Anyone else had these crystals form, is it the phenidone?

Photo Engineer · Aug 31, 2007

sanking said:
Actually not. I only mentioned use of a stirrer hot plate, which does not involve an open flame. I also mentioned warming up the glycol in a water bath. I said nothing about using an open flame, and never have.

Sandy King

Sandy;

Sorry I used too wide a paint brush. My apologies.

Some threads on this topic have had posts advocating the use of a sauce pan over an open flame on a gas stove. I shuddered when I read it. A hot plate can be bad if the water bath is not used because getting a solution up to 100 C can bring the plate to about 200 C depending on plate size and container.

So I was trying to cover all bases at one time.

I've been reading up on hot plates and how they heat trying to find a good plate that does not overshoot and burn an emulsion while finishing. In some cases, the actual heat of the plate does not represent the solution temperature in some cases by as much as 50 - 100 deg C. under manual operation and the overshoot in auto operation is as good or bad as the PID can be. This is as much as 10 - 20 deg C.

PE

sanking · Aug 31, 2007

leicam5 said:
At the risk to be off topic, but while you all (Sandy, Patrick and PE) are on (in?) this threat, I would like to ask for your advice, if you do not mind off course.
A wile ago, I mixed up the 'Warm Tone Pyro Developer for Paper (1947)' formula as posted by Kino here on APUG (10-29-06).
The prescription said to use, among others, 22 grams op 'PYRO', as I did not knew what was intended, I used what I had : Pyrocatechine.
The developer did NOT work, not after doubling the exposure nor after doubling up the dilution.
So, just to be sure, did I had to use Pyrogalol instead of Pyrocat?

Thank you in advance,

Philippe

P.S. Sandy King's Pyrocat-HD is a 'heavenly revelation' to me, and I wonder if this could be used to develop paper....

Another poster already identified the problem I believe. Pyrocatechin requires a higher pH than pyrogallol. You need an activator that will give a working pH of about 10.8 for the pyrocatechin to really kick off. Carbonate is what I recommend, though TSP and the hydroxides could also be used.

I have personally never used Pyrocat-HD to develop paper. Probably a little weak for this purpose. However, Donald Miller has a pyrogallol or pyrocatechin based paper developer. I don't have the formula but you can probably find it with a search of this site.

Sandy King

sanking · Aug 31, 2007

Photo Engineer said:
Some threads on this topic have had posts advocating the use of a sauce pan over an open flame on a gas stove. I shuddered when I read it. A hot plate can be bad if the water bath is not used because getting a solution up to 100 C can bring the plate to about 200 C depending on plate size and container.

We have used electric stoves for so long that I don't even think of the possibility of an open flame when I describe heating up a solution.

Sandy

gainer · Aug 31, 2007

The only electric stove I have is the microwave.

TN98 · Sep 10, 2007

Should I mix the solution B in Glycol or just water?

juan · Sep 10, 2007

Mix solution B in water. Or, figure out how much carbonate is needed in the working solution and simply add that amount directly to the working solution.
juan

gainer · Sep 10, 2007

There is no need for the antioxidant power of bisulfite in the A solution if you are using glycol as solvent. Both sulfite and carbonate can be mixed in water and used as the B solution. Phenidone, catechol and p-aminophenol base are quite soluble in propylene or ethylene glycol. Warming the glycol makes mixing quicker. For the flexibility of being able to vary the ratios of A, B and water in the working solution, one could keep a separate solution C of sulfite or bisulfite which would always be used in amount equal to A. Now one could experiment with ascorbic acid in place of the sulfite by keeping a separate solution of ascorbic acid.

The 1:1:100 A:B:Water working solution would become 1:1:1:100 A:B:C:Water. 1:1.5:100 would be 1:1.5:1:100, and so on.

In the original plan, bisulfite had two purposes, as it does in most developers in which it is used. It served to prevent oxidation of the stock solution, and in the working solution, it enabled the synergism between the catechol and the other agent. Too much sulfite will reduce or destroy the staining power of catechol. Catechol is much more sensitive than pyrogallol in this regard, but the stain color and other factors make catechol more appropriate for certain alternative printing methods. When glycol is used as solvent, the concentration of sulfite ion in the working solution can be optimized without concern for its antioxidant property by keeping it in a separate solution.

Mixing Pyrocat-HD and Propylene Glycol

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