Rollo-TEA

[sanking]

During the last several months I have experimented with a number of variations on existing pyro formulas using both propylene glycol and TEA , or triethanolamine, inspired in part by the recent experiments of Pat Gainer with these agents.

Most recently I did quite a number of tests with a new formula that I call Rollo-TEA. Rollo-TEA, though inspired by the Rollo Pyro formula introduced some years ago by Harald Leban, is an entirely new developer, different from the model in both composition and results.

For 100 ml of stock solution, mix in the order as noted below. For a liter of stock solution multiply the amounts by 10X.

Rollo-TEA

TEA at 175º F
Potassium bromide — 0.2 g
Sodium bisulfite — 2.0 g
Pyrogallol — 15.0 g
Ascorbic acid — 1.0 g
Phenidone — 0.2 g

Add TEA to 100 ml

For use, dilute 1:100 for silver printing or 2:100 for alternative work. Persons who have previously used Rollo Pyro should note that the substitution of phenidone in place of metol at a ratio of one part phenidone for ten parts metol gives a lot of additional synergism to the developer and shortens development times considerably.

The advantage of the Rollo-TEA formula, in comparison to the original Rollo Pyro formula, are as follows.

1. Rollo-TEA is a single solution developer to which one need add only water to have a working solution.

2. With the substitution of phenidone for metol at the ratio of one part phenidone to ten parts metol there is a significant increase in synergism. This gives shorter development times.

3. Very clean working, with very low B+F values.

The color of the stain is typical of pyrogallol based developers, ranging from greenish to greenish/yellow, or yellow/brown. For this reason Rollo-TEA will give results with VC papers similar to PMK and the original Roll-Pyro formula, in contrast to what one might see with the brown stain of developers such as Diaxactol and Pyrocat-HD.


Sandy

 

[gainer]

Not my baby, but I guess it furnishes the sulfite ion that promotes the synergism between pyro and phenidone in the working solution. I think it is a very much more active developer with it than without. Pyro tolerates more sulfite than catechol or hydroquinone before the tanning-staining reduces noticeably.

 

[sanking]

Sandy,

Rollo-TEA looks very similar to the PCP-TEA developer that I've been using, and we've been discussing on the Azo forum.

What is the function of the bisulfite in your Rollo-pyro formula?

Jay

Well, I recall pointing out the same similarity to you on the AZO forum!! But Rollo-TEA is not derived from a combination of PC-TEA and Pyro-TEA, but directly from the Rollo Pyro formula, with the substitution of phenidone for metol at the rate of one part phenidone to ten parts metol. Rollo-TEA is a very versatile staining developer for a wide range of CI because the intensity of the stain remains constant over a wide range of dilutions. Rollo-TEA also produces very low B+F.

I eliminated EDTA from the formula because it is not an active agent, but left in the bisulfite because on mixture with water in the working solution it becomes sulfite. In the original formula the sodium metabisulfite functions primarily as a preservative, but the release of sulfite can also affect the degree of stain. Whether or not the amount of sulfite released is enought to affect the synergism I can not say at this time but since sulfite is known to be an active ingredient in the synergism between phenidione and pyrogallo I thought it prudent to include it in the stock solution for my initial tests with the formula..

Sandy

 

[sanking]

Actually, you suggested that PCP-TEA was similar to Rollo-Pyro, not Rollo-TEA, which is practically identical to PCP-TEA. Sulfite is known to be an active ingredient in the synergism between phenidone and ascorbic acid? I didn't know that. I know that it works that way with Pyro and phenidone, just as ascorbic acid does, but I wasn't aware that sulfite activated the PC synergy. It doesn't seem to have the same effect in PC-TEA. I think it's possible that the bisulfite and ascorbic acid are redundant in your Rollo-TEA formula.

Jay

What I actually suggested was that if you maximized the combination of PC-TEA and Pyro-TEA as a staining developer the result would be very similar to Rollo Pyro, if one were to substitute phenidone for metol. Rollo-TEA is directly derived from the original Rollo Pyro formula, leaving out only the EDTA. The only difference between Rollo-TEA and the original Rollo Pyro formula is that, 1) Rollo-TEA is mixed in TEA instead of water and 2) phenidone has been substituted for metol at the rate of one part phenidone to ten parts metol. The formula is certainly not identical to any combination of PC-TEA and Pyro-TEA that you have proposed.

The statement about the synergism of sulfite was meant to apply to pyrogallol and phenidone, not ascorbic acid. I will edit the original message to avoid confusion.

It is possible that the sulfite may be redundant in the Rollo-TEA formula but only actual testing will tell the truth. I have found that an equal amount of sodium metabisulfite is not redundant in the Pyrocat-HD solution when mixed in glycol. In any event the addition of 2.0 g of sodium metabisulfite per liter of working solution is not high on my list of concerns.

However, I very much doubt that the ascorbic acid is also redundant in the Rollo-TEA formula, as you suggest. In fact, I will bet a lot of money that it plays a very important role both in the total synergism of the formula as well as in minimizing oxidation.

Sandy

 

[sanking]

I meant that the inclusion of both ascorbic acid and bisulfite is redundant. No, your Rollo-TEA is not identical to PCP-TEA as I've specifically described it, but certainly similar enough to be considerd a variation of it. I think that the formula that I've posted is better, because it avoids the redundancy of including both ascorbic acid and bisulfite, which accomplish the same tasks, Benzotriazole is cheaper than KBR, and it uses less pyro to do the same work.

Jay

First, I think we should clarify that PCP-TEA is not a formula, but a combination of two entirely different developers. To provide results similar to what you get with Rollo-TEA requires that you have on hand two separate solutions, since the Pyro-TEA by itself is not nearly so versatile as Rollo-TEA. Rollo-TEA is a specific formula, in one solution, that one simply mixes with water for use. It is entirely based on the Rollo Pyro formula, with the two modifications noted. One could just as easily say that a specific combination of PC-TEA and Pyro-TEA that has the same ingredients in the working solution as Rollo Pyro is a variation of Rollo Pyro, but who cares?

As for Benzotriazole versus potassium bromide, if one does a better job with a certain developer than another then that is the one you should use. The difference in cost would not be a consideration for me since the amounts being used are for all practical purposes inconsequential. A $5.00 bottle of either bromide or Benzotriazole will last a lifetime when added to developers in the quantities required to function as a restrainer.

But how did you determine that benzotriazole uses less pyro to do the same work than potassium bromide? Have you actually run tests of this type?

Sandy

 

[Kirk Keyes]

First, I think we should clarify that PCP-TEA is not a formula, but a combination of two entirely different developers.

Huh? That sounds like the kind of hair-splitting I sometimes do...

Kirk

 

[gainer]

I meant that the inclusion of both ascorbic acid and bisulfite is redundant. No, your Rollo-TEA is not identical to PCP-TEA as I've specifically described it, but certainly similar enough to be considerd a variation of it. I think that the formula that I've posted is better, because it avoids the redundancy of including both ascorbic acid and bisulfite, which accomplish the same tasks, Benzotriazole is cheaper than KBR, and it uses less pyro to do the same work.

Jay

The ascorbic acid and bisulfite do not accomplish the same task unless you limit that task to acidification. Sulfite is not needed for the synergism between phenidone and ascorbic acid, but is when a hydroxybenzene such as pyrogallol, pyrocatechin or hydroquinone is present, whether or not you are trying for tanning-staining action. If you want maximum stain and maximum synergism, use the minimum amount of sulfite. Hydroquinone takes about 1.2 grams of sulfite per gram of hydroquinone for maximum synergism, but that much also gets rid of most of the stain.

If you are using glycol or TEA as a solvent, the sulfite could be used in place of the bisulfite with a little adjustment of pH or development time. The bisulfite is not needed for preservation, but the sulfite ion will still promote the synergism.

A simple way to resolve such an argument is to test with no sulfite, with sulfite and with bisulfite. One can do the same thing with any ingredient. It often happens that an ingredient that is ass-u-med to be necessary is not necessary, but is always added because of custom. As G. K. Chesterton once said " We have passed from the age of common sense to the age of uncommon nonsense."

 

[sanking]

Huh? That sounds like the kind of hair-splitting I sometimes do...

Kirk

I don't see it as splitting hairs but as being precise in the use of terminology. Two part developers typically have one part that contains the reducing agents, restrainer, preservative and other things such as chelating agents, and another part that contains the accelerator (carbonate, metaborate, borax, etc.) Neither part can function by itself as a developer so for use they must be mixed together.

PCP-TEA is a concept rather than a specific formula in that it is based on mixing together in various combinations two different developers, PC-TEA and Pyro-TEA (one staining, the other not) both of which can function on their own. The concept has been used with other developers, Xtol and Rodinal for example, and could just as easily be used with many others. I obviously don't know all of the useful mixtures that could be derived from the mixture of PC-TEA and Pyro-TEA, but on the far ends you would have a formula optimized as a non-staining developer, on the other a formula optimized as a staining developer.

I personally don't see any advantage in the virtually infinite number of variations that are possible, though I can see the advantage of having mixtures optimized for the two extremes, i.e. as staining and non-staining developers. However, Jay has indicated that he is writing an article on PCP-TEA and will hopefully address directly the advantages he finds in the multiple combinations.

My purpose in modifying the Rollo Pyro formula to Rollo-TEA was primarily to show that there are many roads that lead to the same destination. I don't mean to sound overly critical of the PCP-TEA concept but Jay makes it sound better than sliced bread and frankly I just don't get the point because as of yet I have not found anything that I can do with the various mixtures that I could not do just as easily by varying the dilution of formulas such as Pyrocat-HD and Rollo Pyro, and/or by modifying the working solutions of these developers with additional sulfite, ascorbic acid, etc. The main issue with any of the various combinations of PCP-TEA, or in modifying the working solution of known developers, is that the different combinations and modifications affect the energy or working strength of the formula. So the versatility that may seem like an advantage can become a liability because of uncertainity of the result.



Sandy

 

[sanking]

A simple way to resolve such an argument is to test with no sulfite, with sulfite and with bisulfite. One can do the same thing with any ingredient. It often happens that an ingredient that is ass-u-med to be necessary is not necessary, but is always added because of custom. As G. K. Chesterton once said " We have passed from the age of common sense to the age of uncommon nonsense."

Well, I tested the Pyrocat-HD formula with metabisulfite in the stock solution and without it. There was indeed a difference in the amount of stain, i.e. more without that metabisulfite than with it. In due time I will test the Pyro-TEA formula in the same way, or perhaps as you suggest above.

Sandy

 

[Kirk Keyes]

Sandy wrote: "I don't see it as splitting hairs but as being precise in the use of terminology."

Precise? I don't know about that. Whether it was devised by mixing two fully functional developers or mixing parts to create a developer, I don't see where that really matters. Ultimately, developers are just mixtures of chemicals that develop film. Once they are all in the same solution, it may not matter by what mechanism they all got there.

But I do agree with you on the notion that there is a distinct benefit in formulating a developer to take advantage of some property of the film/developer reaction.

"My purpose in modifying the Rollo Pyro formula to Rollo-TEA was primarily to show that there are many roads that lead to the same destination."

Thanks for trying that - as a chemist I always find it interesting the number of ways that similar things can be achieved, sometimes through seemingly different approaches.

"The main issue with any of the various combinations of PCP-TEA, or in modifying the working solution of known developers, is that the different combinations and modifications affect the energy or working strength of the formula. So the versatility that may seem like an advantage can become a liability because of uncertainity of the result."

Right, and that's where picking a set of design criteria or goals, optimizing performance based on those goals, and then determining if those goals have been achieved is useful. And ultimately, this is where the "does everything" approach often fails.

I have come to the conclusion that there are times when you may want a staining developer like PMK or Rollo, and a non-staining developer at other times. Can you think of a time that you would want a half-staining developer?

Kirk - www.keyesphoto.com

 

[gainer]

To whom it may concern: if I made a big stink with rotten TEA, I'm sorry. If I stirred up some gentile controversy, I'm happy. We will all learn something more from it. I know that Sandy and I and others have different photographic objectives, but we all like to have developer stock solutions that last till they are used up. I use staining developers when the spirit moves, but mostly on small or medium cameras that don't strain my 77 year old back and legs. I would rather take pictures of people doing things than of grand scenery, and I don't see much future for me in Pt or even POP printing, but if I find something I think you gentle people might use, I will let you know.

 

[Kirk Keyes]

jdef wrote: "The advantages of the half staining developer that Kirk mentioned, is that it is less grainy than the developer optimized for max. stain and energy, and gives better emulsion speed, but still confers the benefits of a stained negative."

Well, it may have some of the benefits of a fully stained negative. But it will be kind of a compromise.

"I suppose it depends on the characteristics for which one wants to optimize, and to what use the developer is intended."

Which is why it is more useful to formulate for specific characteristics. As we all know, developer formulation is a balancing act of not only the chemicals that go into the formulation, but also the resulting properties of the developer. One of the things I appreciate about Sandy's posts is that he often states what the goals of his formulation variations are striving for.

And Patrick - don't worry about causing stinks - although the TEA by it's nature will smell a bit. Controversy most likely only means that we all have more to learn about these interesting subjects.

Kirk - www.keyesphoto.com

 

[sanking]

One of the things I appreciate about Sandy's posts is that he often states what the goals of his formulation variations are striving for.

Kirk - www.keyesphoto.com

Look first to the essence of what is desired. As Hannibal Lecter said to the young FBI agent Clarice in Silence of the Lambs, "First principles, Clarice. Simplicity. Read Marcus Aurelius. Of each particular thing, ask: 'What is it in itself, what is its nature?' What does he do, this man you seek?

Had Marcus Aurelius lived in the age of photography he no doubt would have looked for first principles in developers.


Sandy

 

[Maine-iac]

If I stirred up some gentile controversy, I'm happy.

My Jewish friends will be happy to know that they don't have a lock on controversies, but that we goyim can hold our own.

Larry

 

[sanking]

I believe in the PCP-TEA concept, and am working to address the shortcomings that I have found. I thank Sandy for his help in identifying these problems, and offering suggestions to address them, even though he doesn't share my enthusiasm for the larger concept.

Jay

Jay,

It might be incorrect to say that I don't share your enthusiasm for the larger concept. I think it would be more accurate to say simply that I don't really understand what you mean by the larger concept. But I do share your enthusiasm for experimenting with developer formulas to make them better so why don't we just agree that this is the larger concept.

However, I may be wrong about TEA. My previous thinking has been that with any given formula the energy, or synergism of the reducing agents, was determined by the pH of the working solution. However, after looking at some of my data from the recent tests with Rollo Pyro that I described on the AZO forum it now appears to me TEA may provide some additional synergism beyond what one would expect merely on the basis of the pH it gives to the working solution. I missed out on this in my earlier analysis of the results of those tests because of an error in reading pH. However, after looking again at the results I am seeing a rather clear indication that the Rollo Pyro solutions mixed with TEA, which give a working pH of around 9.3, were more energetic than the same solutions when using metaborate as the accelerator, with a pH of around 9.8. Of course these inexpensive pH meters that I use are subject to a lot of error so I could be wrong about this but my impression at this point is that the TEA contains something that provides greater synergism, at least with the Rollo Pyro formula, than would be suggested by the pH itself. Hopefully Pat Gainer will have some additional thoughts on the subject.

Sandy

 

[Kirk Keyes]

Had Marcus Aurelius lived in the age of photography he no doubt would have looked for first principles in developers.Sandy

Yes, I agree! While there is much to be said for a developer that is moderate in it's properties, I think Marcus Aurelius would have also recognized that each formulation should try to be virtuous in its first principles.

As Marcus Aurelius has been one of those people that has had a major influence on my outlook on life, here are a couple of quotes of his that may be applied to this discussion:

"Nothing has such power to broaden the mind as the ability to investigate systematically and truly all that comes under thy observation in life."

"We are too much accustomed to attribute to a single cause that which is the product of several, and the majority of our controversies come from that."

Marcus Aurelius

 

[Kirk Keyes]

However, I may be wrong about TEA. My previous thinking has been that with any given formula the energy, or synergism of the reducing agents, was determined by the pH of the working solution.

Developer energy is not as simple as mere pH. Your recent tests with sodium sulfite levels have proven that to yourself.

I don't remember which forum it was that you asked this Sandy, but you were wondering about the shelf life of sodium sulfite solutions. Sulfite is an oxygen scavenger and will react with oxygen from the air. So the trick is to store solutions in glass bottles, with impermeable caps - teflon lined should work well. Solutions stored in these conditions shold last for quite some time, much more than the few hours that I think you hypothesised.

There are pretty easy methods using titration to measure sulfite in solution, but for the experimental work you are doing, you may just want to measure out small amounts of sulfite as a powder, and add it directly to the solution. That way you will be confident of the final concentration.

And for pH, they do make pH electrodes that are designed to perform better at higher pH levels, and also ones at high levels of sodium concnetration. Look for electrodes that are liquid filled - not gel filled. You will probably not find a "stick"-type meter with a liquid filled electrode, so it may be worthwhile getting a more expensive meter and electrode for your measurements. (I'm assuming you have one of the more inexpensive stick meters at this point...)

I don't know what control samples/standards you are using to verify your pH measurements, but they make a wide range of pH standards that are not very expensive. You may want to get a series of these standards that go through the range of pH that you are interested in. You could use a couple to calibrate your meter, and then use some other standards that lie between your calibration points to verify the calibration. pH standards can commonly be found at pH 7, 7.4, 8, 9, 9.2, 10, 11, and 12.4. (I would recommend not using the 12.4 to calibrate with though, unless you are really working at that level.) But that's quite a good range to pick from!

Kirk - www.keyesphoto.com

 

[gainer]

It is easy to show that a very small amount of sulfite in a PQ or MQ developer gives a great increase in the acitvity as compared to no sulfite. A difference between PQ and PC is that there is no corresponding increase in activity with addition of sulfite. A simple PC developer will also not show a great increase in activity with addition of hydroquinone. Add a tiny amount of sulfite and watch it go.

Mostly this means that there is some difference between hydroquinone and ascorbate in the the way they work. I recently tried adding some hydroquinone to Rodinal. As you remember, when I first added sodium ascorbate to Rodinal, I found it reduced grain, increased activity of a 1+50 solution to that of a 1+25 solution, and improved resolution.

When I added hydroquinone to the commercial stock solution, the first thing that happened was precipitation of the sort that happens when I mixed Rodinal according to the kit sold by Photographer's Formulary. I added 50% lye solution a little at a time to dissolve the crystals. The result was a pretty dark but clear solution which I used anyway as iif it were Rodinal. The results were quite good at 1+50 on HP5+.

I think the same would have happened if I had added ascorbic acid to commercial Rodinal. I still have to try that.

I have a lot of fun doing such dumb stunts because, as I think I said before, I was born in West Virginia where "Montani Semper Liberi" and raised in Missouri, which is the "Show Me" state.

 

[gainer]

I guess what I should have said is that superadditivity between metol or phenidone and hydroquinone, catechol or pyrogallol is really a 3-way system, a menage a trois, involving sulfite. Superadditivity between ascorbic acid and metol or phenidone is a 2-way affair. Making it a 3-way system by adding hydroquinone, will not give you much change in activity unles you also add sulfite.

 

[sanking]

I don't know what control samples/standards you are using to verify your pH measurements, but they make a wide range of pH standards that are not very expensive. You may want to get a series of these standards that go through the range of pH that you are interested in. You could use a couple to calibrate your meter, and then use some other standards that lie between your calibration points to verify the calibration. pH standards can commonly be found at pH 7, 7.4, 8, 9, 9.2, 10, 11, and 12.4. (I would recommend not using the 12.4 to calibrate with though, unless you are really working at that level.) But that's quite a good range to pick from!

Kirk - www.keyesphoto.com

Kirk,

I am using two pH measuring instruments at this time, both by Oaklon. One is the pH Testr 1, the other their pH Wand. Both provide very consistent readings from as low as pH 1.5 to as high as pH 15.0, but they are off (relative to each othe) by about pH 0.3 in the pH 8.0 to 12.0 range. I don't know which of the meters is most accurate, but at least they are consistent in readings within the range noted.

I would be very appreciative if you would send me the address/email/website of a company that can provide control samples/standards to verify pH measurements. I have use in the past pH strip indicators but these have almost always proven to be less accurate than my instruments.

Sandy

 

[sanking]

I am attaching two CI charts for the Rollo-TEA formula introduced in this thread. One is based on blue analysis and would apply to printing with silver papers, including AZO, the second is based on UV analysis and applies to printing with UV sensitive alternative processes. Remember, for silver printing you need a negative with a CI of about, .55, for AZO and palladium printing about .75 - .85, and .85 or higher for VDB, albumen and salted paper.

The film used was FP4+ and development was in rotary processing, with constant but fairly gentle agitation, at 72º F.

To repeat, Rollo-TEA is a pyrogallol based developer that is mixed in TEA (triethanolamine) and needs only water for activation as a developer. Here are the mixing instructions, slightly modified from my original message.

Rollo-TEA

For 100 ml of stock solution, mix in the order as noted below. For a liter of stock solution multiply the amounts by 10X. Start with about 80 ml of a TEA solution at 250º F. 80 ml will heat in my microwave to 250º F in about 30 seconds. Be very careful with the hot solution.

First add,
Potassium bromide — 0.2 g
Sodium bisulfite — 2.0 g

Allow the above solution to cool to 170ºF and then add,

Pyrogallol — 15.0 g
Ascorbic acid — 1.0 g
Phenidone — 0.2 g

Add TEA to 100 ml. When using fresh solutions and mixing as directed above the final solution will have a slight coloration, similar to a very light drinking tea.

For use, dilute 1:100.

The CI charts indicate that Rollo-TEA, diluted 1:100, has about the same energy level, or just slightly less, than a 2:2:100 dilution of Pyrocat-HD. You can dilute it 2:100 for a much faster working developer if required. You could also dilute 1:150 or 1:200 for a slower acting developer.

After looking carefully at the characteristics of Rollo-TEA I do not see that it offers any particular advantage for my own work over Pyrocat-HD. However, those who like the results they get with PMK and Rollo Pyro should consider the Rollo-TEA formula since by simple dilution it can duplicate the action of either, and there is the additional advantage of the fact that only one solution, which should last for a very, very long time, is needed. Moreover, because the pH of a working solution of Rollo-TEA is about pH 0.5 lower than working solutions of PMK and Rollo Pyro. I suspect that the grain of Rollo-TEA will be slightly finer than what one sees with these two developers.

One of my objectives in formulating a developer is to use as little of the primary reducing agent as possible. This makes sense from a ecological perspective, and there is also some evidence that developers that contain very low amounts of th primary reducer give higher definition. This was one of my main objectives with the Pyrocat-HD formula, which with the 1:1:100 dilution contains half as much procatechin as there is pyrogallol in a 1:2:100 dilution of PMK, yet is slightly more active. Based on the same criteria the Rollo-TEA formula might be seen as a more elegant formula than either PMK or Rollo Pyro because for a given amount of pyrogallol it has a much higher level of activity. For example, for a given amount of working solution the 1:100 dilution of Rollo-TEA has only 1/2 of the amount of pyrogallol as there is in a 2:4:100 working solution of Rollo Pyro, but energy level is almost identical.

I do want to again emphasize that the color of the stain you get with Rollo-TEA is typical of pyrogallol based developers, i.e. greenish to greenish/yellow/brown. One should therefore expect that results with VC papers with Rollo-TEA will be quite similar to what one gets with PMK and Rollo Pyro, in contrast to the results obtained with these papers with the brown stain of pyrocatechin based developers such as Diaxactol and Pyrocat-HD.

Sandy

 

[sanking]

Sandy,

while I do enjoy playing around with developer formulae, the larger concept that I aspire to, is to make use of the unique attributes of TEA, to formulate a superversatile developer system.

I am confident that the optimum proprtions of the two parts will be identified with further experimentation. Thank you for your insights.

Jay

If that is your purpose I do not disagree with it at all. But to reach your goal will require first and foremost definining rather precisely what it is that you want to achieve, and then devising an efficient testing methodology for taking you there. Do you want a system for small format films that emphasizes fine grain or one for medium and large format films where acutance is more important than grain? Do you want a system for regular silver printing, for AZO or for one of the alternative processes? Or do you want a dual purpose negative that will print with the same contrast in silver and in an alternative process? And if the latter is what you want then you must determine what color stain would serve you best, the greenish stain of pyrogallol based developers, the reddish-brown stain of hydroquinone, or the brownish/black stain of pyrocatechin based developers?

And if you are going to do this I think you will need to learn more about the use of applied sensitometry than your messages to this point suggest that you know. I don't say this with any intent to be insulting but the intelligent use of sensitometry will make your work much more efficient, and the data can also be presented for others to check. I always try to show exactly how I test so that others can check for themselves the accuracy of my results. This is an essential part of the process because we all make mistakes and the insights of others are often very helpful. One of the main reasons the Pyrocat-HD formula has proven so popular is because of adjustments to the formula that have been made at the suggestion of others. And as you know I am continuing to improve the formula as I learn more: more stability when mixed in glycol, greater synergism with the addition of ascorbic acid, the ability to provide greater synergism with no stain when desired by the addition of sulfite. The problem is that every change made to the basic formula requires the generation of new film development data for every film. The efficient use of sensitometry, which for me means use of the BTZS system of testing, is one of the keys to being able to efficiently generate this type of data.


All that said, I wish you much success in your project, and am ready to assist you in any way possible.

Sandy

 

[fhovie]

Sandy:

My first batch of Pyrocat HD is about used up .... Should I run out and get some glycol - If I follow the not broken/don't fix it idea - It is working fine. I have TEA but no glycol - maybe I'll just mix another batch unless you recomend otherwise. I have been very happy with it. I was also very happy with PMK but the PyrocatHD, I am certain gives finer grain with all the tanning, compensating benefits of PMK.

 

[skahde]

Recently I played a bit with the formula of Pyrocat-HD and modified the amount of metabisulfite: doubling it gets you more or less rid of the stain, at least when developing Delta 100. For me this was quite a surprise as with the usual 1+1+100 dilution you end up with just 200mg/L..

Stefan

 

[sanking]

Sandy:

My first batch of Pyrocat HD is about used up .... Should I run out and get some glycol - If I follow the not broken/don't fix it idea - It is working fine. I have TEA but no glycol - maybe I'll just mix another batch unless you recomend otherwise. I have been very happy with it. I was also very happy with PMK but the PyrocatHD, I am certain gives finer grain with all the tanning, compensating benefits of PMK.

I would recommend that you continue to mix the Pyrocat-HD stock solutions in distilled water, and in relatively small quantities, until you learn enough about the developer to know that it is something you want to use for the long haul. If you mix it in small amount, say 100ml to 500ml, chances are that you will use it up long before it goes bad, since the stock A solution will last for up to a year with little or no change in working characteristics.

The use of glycol does not add anything at all to the developer other than keeping quality, and the process of mixing requires high temperature solutions that pose some potential risk.

I do not recommend mixing Pyrocat-HD in -TEA, at least at this time. My initial tests with Pyrocat-HD in TEA have shown that for the same amount of pyrocatechin in the working solution longer time of development are required to reach a given CI than if the stock solutions are mixed in water or glycol. It may be possible to adjust this by adding a little ascorbic acid to the mix but as yet I have not tested the concept.

Sandy