PyroCat HD

[clay]

Clearly the idea that 100g in 100ml of water constitutes a 100% solution is not correct. There was a raging debate on the B&S forum about a year ago about this, with the people who have never taken chemistry insistent that this would indeed be a 100% solution. Nevertheless, the formula as printed in unblinkingeye.com IS correct in the amounts it calls for. Keep in mind that the catechol is the main developing agent, not the phenidone. All I can say is that this developer blows the socks off of any other staining developer in terms of sharpness, low b+f, and predictability.

Clay

 

[Jorge]

Ole, I am using potassium hydroxide 10% for the B solution and it works great. The Sodium Carbonate has to be diluted more.

 

[Ole]

Jorge, how much of the hydroxde do you use? Same proportions (1:1:100), or more?

(It probably doesn't matter, as the total OH- activity will be high enough to activate the developer anyway. There is a LOT more alkali than developer in that mix!)

BTW; there's a zero too many in my previous post: A liter of developer contains 0.002g phenidone, not 0.0002. Still a very small amount...

 

[sanking]

Somewhere in the past I learned that a percent solution is based on the number of grams of a chemical in a given amount of water. Therefore, a 1% potassium carbonate solution is made up of one gram of potassium carbonate in 100ml of water, or 10grams of potassium carbonate in 1000ml of water. Many photograhic texts continue to describe a percent solution in this way.

From the discussions on this topic last year on the alt-photo-process list I learned that chemists describe the term percent solution in a different way, so that 100g of potassium carbonate in 100ml of water is not exactly a 100% solution. However, I have no practical way of adopting the measuring system of the chemicsts so I will continue to refer to the Pyrocat-B stock as a 100% solution of potassium carbonate.

It is possible to substitute sodium carbonate for potassium carbonate with Pyrocat-HD. To do so, prepare a 20% stock solution of sodium carbonate, i.e. 20g of sodium carbonate in 100ml of water. To prepare a working solution dilute 1 Part A + 5 Parts B + 100 parts water. This working solution will have working qualities very close to the 1:1:100 dilution made up from a 100% potassium carbonate stock solution.

Potassium hydroxide will also work as the accelerator but my tests indicate that its use results in slightly larger grain than the carbonates.

Sandy King

 

[sanking]

Quoting from a previous message,


"At 1:1:100, the total concentration of pyrocatechol will be 0.05g/liter, plus 0.0002g Phenidone. This is less than a fifth of the lowest concentration in any other developer formula?"

The very small amount of reducing elements in a liter of working solution is one of the reasons for the outstanding sharpness of the Pyrocat-HD formula. As a rule develolpers with very small amounts of reducing elements tend to give sharper negatives than those with larger amounts. D76 1:1, for example, is visibly sharper than D76 straight.

Regarding the amount of Phenidone, I see that you corrected in another message the above amount. The amount is still very small, but phenidone is strongly super-additive with pyrocatechin, and it also has strong regenerative qualities. And at the given amount of 0.002g per liter of working solution it plays a very big role in development. Metol, even when substituted in the PyrocatHD formla at 10X the amount of phenidone, impacts develoment less than phenidone.

Sandy King

 

[Ole]

Thank you very much, mr. King!

I'll try this with the next batch of film, at the moment the weather's so bad I wouldn't go outside myself, much less with a camera!

My gripe with the percentage is this:

Adding 1g chemical to 100cc water is a 1% solution, or at least very close to it.
Adding 100g chemical to 100cc water is a 50% solution by weight (100+100=200), NOT 100%.
Taking 100g chemical and adding water to 100cc, the concentration depends on the density of the chemical, but as it will contain 1g chemical per cc of solution, I might be willing to let it pass as 100% - although it's wrong...

 

[sanking]

I am frankly quite confused by the question of percent solution. Out of curiosity I just added 100g of potasssium carbonate to 100ml of water. This gave a total volume of 137ml of Pyrocat-HD stock solution? Would I be correct to assume that this constitutes a percent solution of potassium carbonate of approximately 73%, i.e. 100/137?

Regardless of any confusion about how to determine a percent solution the formula at Unblinking Eye is correct: 100g of potassium carbonate in 100ml ofwater.

Sandy King

 

[avandesande]

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (sanking @ Apr 2 2003, 05:15 AM)</td></tr><tr><td id='QUOTE'>I am frankly quite confused by the question of percent solution. Out of curiosity I just added 100g&nbsp; of potasssium carbonate to 100ml of water. This gave a total volume of 137ml of Pyrocat-HD stock solution? Would I be correct to assume that this constitutes a percent solution of potassium carbonate of approximately 73%, i.e. 100/137?

Regardless of any confusion about how to determine a percent solution the formula at Unblinking Eye is correct: 100g of potassium carbonate in 100ml ofwater.

Sandy King</td></tr></table><span class='postcolor'>
You are making things much too complicated. You want to add a given weight to a given volume, so it makes it easy to add a desired amount per volume.
For instance::

Add 50 grams sodium carbonate to 50 ml of water, dissolve, and add enough water to 'make' 100 ml of solution. You know that to get 1 gram of carbonate into your final batch, you need to add 2ml of your solution, it's a 2:1 ratio.

Forget about percents...

If you would like, point me to a process you are trying to work out, and I will show you how to streamline it.

I am sorry if I sound a little bossy, I may be a baby at photography, but I do know chemistry.

--Aaron

 

[Ole]

</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (sanking @ Apr 2 2003, 05:15 AM)</td></tr><tr><td id='QUOTE'> I am frankly quite confused by the question of percent solution. Out of curiosity I just added 100g of potasssium carbonate to 100ml of water. This gave a total volume of 137ml of Pyrocat-HD stock solution? Would I be correct to assume that this constitutes a percent solution of potassium carbonate of approximately 73%, i.e. 100/137?
</td></tr></table><span class='postcolor'>
All that means is that the finished solution has a density of 1.46 SG - so 1ml weighs 1.46 gram. Your 200 gram total has a volume of 137ml, 200/137=1.46. So the concentration of the solution is 73% weight/volume (correct!), or 50% weight/weight...

With "normal" solutions up to about 10% or so this differende can be neglected, but with this kind of concentration it can be very confusing - and imprecise.

A better way to make the specified solution B would be to take 73g potassium carbonate and add water to 100ml. This gives a specified amount of chemical in a specified end volume - so I know what size bottle to put it in...

 

[Aggie]

..

 

[avandesande]

There is nothing really wrong with making solutions this way, it is just confusing, and is inconsistent from the way the other solutions are mixed.

What i really hate is when differnt units are used, like the ABC formula on Ron Wisner's site. Mixing grams and ounces gives me a headache.

 

[Jorge]

Ole, I use it just as Clay specified in his article, for pt/pd printing I use 1:2.100. But I suppose for normal silver printing the 1:1:100 solution would work just fine.

As to the percent solution Ole is correct if one wants to be absolutely accurate. With low percent solutions the change in density is minimal and thus it can be ignored, at high concentrations, such as a 50/50 it is important, but for photographic purposes the "nomenclature" can be ignored and use the mixing instructions as given by Sandy. One more wrinkle would be that a true 100% solution would probably not dissolve as it has reached its saturation point. This is why 100gr of NaCO3 can dissolve in 100 ml of water, as it has not reached its saturation point, since it is only a 73% solution as explained above. In any case dont worry about it, just do it as Sandy said, it works great.

 

[Ole]

Oh, I'll try it - as soon as I have some new negatives to develop. Tomorrow, or thereabout

The main reason (besides being really uptight when it comes to chemistry) behind my inquiry was that I have no potaiium carbonate, so will have to substitute something else. Or wait a month, which I don't want to do. So I wanted to know what to make of the recipe as stated (a formula requires a bit more precision, IMO)...

So I'll work out the equimolar sodium equivalent of the 73% weight/volume potassium carbonate solution, and happily try that! I'll even post the results here.

BTW; it's possible to make more than 100% solutions of some chemicals. Hypo springs to mind - the crystalline version contains more water than a saturated soltion would...

 

[clay]

I can't say that I've actually tried this, but I have heard that the pH+ often found in pool supply stores is reasonably pure potassium carbonate. You might want to check around and save yourself a wait.

Clay [saturated at an 11% solution :^) ]

 

[sanking]

It is my understanding from readings in Mees and Haist that in most developing formulas potassium and sodium carbonate are interchangeable on a per weight basis, though I have never considered the difference in molecular weight. Just making allowance for monohydrate and anhydrous forms gives me enough of a headache as it is without looking for more trouble.

In any event, all of my experiments (which include extensive testing with curve plotting) show that in the pyrocat formula the sodium and potassium forms of carbonate can be substituted on a one to one ratio in terms of weight, with no change in the working characteristics of the developer. In fact, all of my earlier experiments with Pyrocat were carried out with sodium carbonate with B solutions of 10g - 20 g of carbonate to 100ml of water. Later I found that potassium carbonate would go into solution at a much higher concentration that sodium carbonate and decided to switch to the 100g potassium carbonate to 100ml of water because it allowed a very practical dilution of 1:1:100.

So the bottom line is that you don't really need to test this premise. I call tell you for a fact that a 1:5:100 working dilution mixed from a B solution of 20g sodium carbonate per 100ml of water will give curves that are virtually identical for the same time and temperature of development as a 1:1:100 working dilution mixed from a B solution of 100g of potassium carbonate per 100ml of water. The fact that the 1:5:100 solution is slightly more diluted than the 1:1:100 solution does not appear to result in any measurable difference in the curves.

And I guess that is just about all of the meaningful information I can share with you on this subject!!

Sandy King

 

[GreyWolf]

I have just read through this whole thread and wish to thank Sandy for providing me and most certainly others with a wealth of information.

In regards to the solution ratio debate, I (and I believe probably most others) could not give a damn about how the "official" way of doing it is. In Sandy's explanations he gives a simple example (which is both illustrative as well as a working example) of how to achieve the appropriate mix for the application.

If I want to adjust the total volume of solution "B" or determine how much of a specific chemical I wish to buy I can easily do that by performing simple arithmetic on the examples given.

After awhile reading silly "just to be right" replies gets to be a little tiring. Thankfully Sandy preserved and we all received the useful information intended from this thread.

Regards,

 

[Eric Rose]

Now now Greywolf, do we need to get out and take some pics? Or is the snow getting to ya LOL! I agree with you, but for some the chemistry side of it is part of the enjoyment. Not mine, but then you'd never get me printing step wedges either!

Just joking here old buddy.

Eric

 

[LFGuy]

I just tried the 2:2:100 dilution over the weekend, and it worked out pretty well for me over 1:2:100 (for alt processes).

By the way, I just noticed you can buy Pyrocat-HD kits from Photographers' Formulary, if you don't like mixing it yourself (which is really easy, by the way). http://www.photoformulary.com/filmdev.htm

$11.95 USD for 10 L working solution (I'm guessing that's at a 1:1:100 dilution). I'd have to look at prices next time I need to buy chemicals, but I'm sure it's cheaper mixing it yourself.

 

[sanking]

There is no question but that mixing Pyrocat-HD from scratch will work out to be a lot less expensive than buying the kit.

Just a word or two on mixing. Mixing of Pyrocat-HD from scratch is pretty routine but there are two areas where some extra instructions might come in hand.

First, phenidone is rather hard to get into solution. A solution to this problem is to first mix the phenidone with a small amount of alcohol (90% isopropyl best) and then add this to the stock mixture. Be assured that this will have no impact on the working qualities of the developer.

Also, when mixing the potassium carbonate please be sure to add the carbonate to the water very slowly, while mixing. When mixing the carbonate with water an exothermic reaction takes place and if one adds the carbonate too fast to the water the solution will get very hot.

Finally, do allow the stock solutions to stand for an hour or so to allow all of the chemicals to go into solution.

Sandy King

 

[Ole]

Another convert here!

Finally got around to a "proper" test - with the stock I mixed a month ago. The negs I developed then were inconclusive, as I used a new (to me) film, a new (to me) developer, a new (to me) process - inspection - in my new darkroom. Too many variables...

This time I developed two rolls of Ilford Pan F+ for 9 minutes using 1:1:60 dilution. Beautiful negatives, with full details in both shadows and (extreme) highlights.

A third roll, Kodak Plus-X, also looks promising at 8min; but as I'm not that familiar with this emulsion I can't evaluate it before printing.

BTW, I used 6.3g Sodium Carbonate instead of stock B. Thanks, Sandy, for measuring your solution!