Pyrocathecol, catechol age

haryanto · Feb 2, 2007

so there's 2 opinions about lifespan catechol in PG, I've already store my cathecol in dissolve in PG, hope it will have long lifespan

thanks Jed, Sandy and others

btw, Sandy, how you dissolve ascorbic acid in pyrocat MC, I cannot fully dissolved AA, I made it as gainer explained somewhere in this forum, metol + AA + TEA + water (a spoon) to make slurry then + warm PG

sanking · Feb 2, 2007

haryanto said:
so there's 2 opinions about lifespan catechol in PG, I've already store my cathecol in dissolve in PG, hope it will have long lifespan

thanks Jed, Sandy and others

btw, Sandy, how you dissolve ascorbic acid in pyrocat MC, I cannot fully dissolved AA, I made it as gainer explained somewhere in this forum, metol + AA + TEA + water (a spoon) to make slurry then + warm PG

The ascorbic acid will dissolve in warm propylene glycol at about 120ºF if you give it enough time. More heat makes it dissolve faster, though it is best to keep the temperature below 150ºF. A magnetic hot plate stirrer is great for mixing chemicals and if you spend much time mixing your own formulas I would stongly recommend that you purchase one. They are relatively in-expensive on ebay.

You could also dissolve the ascorbic in a small amount (25ml) of very hot (175-200ºF) distiled water, and then add this to the larger solution.

Sandy

haryanto · Feb 2, 2007

sanking said:
The ascorbic acid will dissolve in warm propylene glycol at about 120ºF if you give it enough time. More heat makes it dissolve faster, though it is best to keep the temperature below 150ºF. A magnetic hot plate stirrer is great for mixing chemicals and if you spend much time mixing your own formulas I would stongly recommend that you purchase one. They are relatively in-expensive on ebay.

You could also dissolve the ascorbic in a small amount (25ml) of very hot (175-200ºF) distiled water, and then add this to the larger solution.

Sandy

many thanks for quick reply Sandy, I'll try to find magnetic stirring

pauldc · Feb 2, 2007

Thanks too Sandy - very clear

Tom Hoskinson · Feb 2, 2007

Jed Freudenthal said:
Pyrocatechol will be stable for a long time (years) . Even if it is light brown or tan, it can be used. I once dissolved it in propylene glycol. Then it is unstable. In the first few days the development activity will increase and thereafter it will decrease again. Anyway, byproducts are apparently created.
I use the pyrocatechol straight, as they do in Europe for over one century. A fresh pyrocatechol often has a strong phenolic odor. When the pyrocatechol becomes older, the odor will disappear. If you do not like that odor or want to be sure for toxic reasons, just weigh and dissolve the pyrocatechol (on a safe place) outside if you do not have a fume hood.

Jed

Jed, you stated: "I once dissolved it in propylene glycol. Then it is unstable. In the first few days the development activity will increase and thereafter it will decrease again. Anyway, byproducts are apparently created."

Jed, what you have stated does not agree with my experience and my experimental results (which I have described elswhere in this thread).

Jed, Please post the details of your compounding and testing procedures for a stock solution of catechol dissolved in propylene glycol that behaved in the manner you described; and/or for a catechol based developer dissolved in propylene glycol that behaved in the manner you described.

Tom Hoskinson · Feb 2, 2007

pauldc said:
And do I understand it correctly that by making a Pyrocat A solution in proylene glycol as Tom explained in this thread then I only need to use catechol and phenidone and I can dispense with the potassium bromide and sodium metabisulphite that I would normally use when making the A solution in a water base?

If so, this would be much simpler as well as having a good lifespan

Paul, I started mixing Pyrocat A in propylene glycol without the potassium bromide and sodium metabisulphite strictly for the ease of mixing. I reasoned that I could add the potassium bromide and sodium metabisulfite later in the form of a second stock solution (as Sandy King describes later in this thread).

My testing results show that for the films I am developing, I get very similar (and acceptable to me) results without adding the potassium bromide and sodium metabisulfite to the Pyrocat A solution - or to the B Solution.

pauldc · Feb 2, 2007

Tom Hoskinson said:
My testing results show that for the films I am developing, I get very similar (and acceptable to me) results without adding the potassium bromide and sodium metabisulfite to the Pyrocat A solution - or to the B Solution.

Thanks for the advice Tom. This appeals to me as it is wonderfully simple and I will give it a go.

Jed Freudenthal · Feb 3, 2007

Tom Hoskinson said:
Jed, you stated: "I once dissolved it in propylene glycol. Then it is unstable. In the first few days the development activity will increase and thereafter it will decrease again. Anyway, byproducts are apparently created."

Jed, what you have stated does not agree with my experience and my experimental results (which I have described elswhere in this thread).

Jed, Please post the details of your compounding and testing procedures for a stock solution of catechol dissolved in propylene glycol that behaved in the manner you described; and/or for a catechol based developer dissolved in propylene glycol that behaved in the manner you described.

Tom,
Some time ago, I published a catechol and a pyrogallol formula on the APUG web site under the title 'high definition developers, staining and non-staining'. Here, I am referring to experiments with the catechol developer, which is a non-staining developer, and I never saw publications on this kind of developer ( since 1895) with staining action. The silver deposit is, however, slightly brownish coloured, because the deposit is very fine. It is no stain. I mentione this because you were sure there is a staining action and here our observations differ.
At the same time, you suggested to dissolve the catechol in propylene glycol, because of the ease of use ( and for toxicity reasons).
Now the experiment: As you know catechol, as used by photographers, is never really catechol. I have fresh white coloured catechol up to seventy years old almost black catechol. I selected a 'representative' catechol of a few years old, slightly brown colored and quite stable considering the time span I will use that batch of catechol. I dissolved this catechol in propylene glycol and let it stand for approximately one hour. Then I made a comparative test using my high definition developer catechol 'straight' and 'mixed in propylene glycol'. I found that the development activity of the 'mixed in propylene glycol' catechol was higher than the 'straight' catechol. After a couple of days I repeated the experiment. The 'straight' catechol remained stable ( but I knew that) and the 'mixed in propylene glycol' was down, even lower than 'straight' catechol. The 'mixed in propylene glycol' will probably go to an equilibrium situation, but I did not check that. My assumption was that the catechol and its byproducts are going to an state of equilibrium eventually. I do not like a situation like that from the point of view of reproducibilty in density and image quality. And I still mix the catechol in its dry form.
Interestingly to note is that the 'dry mixing' of catechol of different batches gives different activities. A fresh batch is more active than an older browner batch. But that is all I can observe. My conclusion is that the byproducts of catechol have a lower activity than catechol itself. My suspicion is that there might be a reaction between propylene glycol and the byproducts. But in reality, we must accept the presence of byproducts.

Jed

Tom Hoskinson · Feb 3, 2007

Jed Freudenthal said:
Tom,
Some time ago, I published a catechol and a pyrogallol formula on the APUG web site under the title 'high definition developers, staining and non-staining'. Here, I am referring to experiments with the catechol developer, which is a non-staining developer, and I never saw publications on this kind of developer ( since 1895) with staining action. The silver deposit is, however, slightly brownish coloured, because the deposit is very fine. It is no stain. I mentione this because you were sure there is a staining action and here our observations differ.
At the same time, you suggested to dissolve the catechol in propylene glycol, because of the ease of use ( and for toxicity reasons).
Now the experiment: As you know catechol, as used by photographers, is never really catechol. I have fresh white coloured catechol up to seventy years old almost black catechol. I selected a 'representative' catechol of a few years old, slightly brown colored and quite stable considering the time span I will use that batch of catechol. I dissolved this catechol in propylene glycol and let it stand for approximately one hour. Then I made a comparative test using my high definition developer catechol 'straight' and 'mixed in propylene glycol'. I found that the development activity of the 'mixed in propylene glycol' catechol was higher than the 'straight' catechol. After a couple of days I repeated the experiment. The 'straight' catechol remained stable ( but I knew that) and the 'mixed in propylene glycol' was down, even lower than 'straight' catechol. The 'mixed in propylene glycol' will probably go to an equilibrium situation, but I did not check that. My assumption was that the catechol and its byproducts are going to an state of equilibrium eventually. I do not like a situation like that from the point of view of reproducibilty in density and image quality. And I still mix the catechol in its dry form.
Interestingly to note is that the 'dry mixing' of catechol of different batches gives different activities. A fresh batch is more active than an older browner batch. But that is all I can observe. My conclusion is that the byproducts of catechol have a lower activity than catechol itself. My suspicion is that there might be a reaction between propylene glycol and the byproducts. But in reality, we must accept the presence of byproducts.

Jed

Jed, you have replied to my question with subjective opinions, guesses and conjectures - but no data.

I would like to see the details of the experimental design you employed to examine and document any chemical reactions that occurred between catechol and propylene glycol and the data results produced by the execution of the experiment.

Jed Freudenthal · Feb 4, 2007

Tom Hoskinson said:
Jed, you have replied to my question with subjective opinions, guesses and conjectures - but no data.

I would like to see the details of the experimental design you employed to examine and document any chemical reactions that occurred between catechol and propylene glycol and the data results produced by the execution of the experiment.

Tom, what are my subjective opinions, guesses and conjectures ? When I say there is no stain, there is no stain. You are saying there is stain, but do not mentione the level of stain. I cannot imagine what to add to the recipe/experiment, as described in the article at the APUG site 'high definition developers, staining and non-staining'. Nobody asked me for more clarification. And the formulas are in use for many years.
As you know, catechol 100% cannot exist, because it is degrading all the time. It would be an enormous analytical task to study the chemical reactions of propylene glycol with catechol and its degradation products as a function of time. And I certainly would not publish the results on the APUG site.
Over one century catechol has been put in the developer succesfully as a dry substance. A year or so ago, somebody came up with the idea to put it in propylene glycol. first. And now I have to proof that it gives problems:rolleyes:
I would say: you have to proof that it doesn't give problems.
I approached the design of the catechol (HD) formula in such way that it could stand the variations in catechol purity (natural degradation products). All one has to do with an 'old' catechol is to increase the amount of catechol. The strong point of this catechol HD developer is the simplicity. All there is: is a development agent and an alkali (with a very small amount of sudium sulfite).

Jed

mikebarger · Feb 4, 2007

I've only used TEA to mix the pyro formula I've been using. Guess I've used HC110 for so many years I like the heavier developer.

If/Can TEA is used rather than propylene glycol, is it a straight across replacement for the glycol?

Sorry if this is too simple of a question, no high school or college chemistry.

Mike

Tom Hoskinson · Feb 5, 2007

mikebarger said:
I've only used TEA to mix the pyro formula I've been using. Guess I've used HC110 for so many years I like the heavier developer.

If/Can TEA is used rather than propylene glycol, is it a straight across replacement for the glycol?

Sorry if this is too simple of a question, no high school or college chemistry.

Mike

Perfectly reasonable question, Mike. The answer is no, TEA cannot be used as a straight across replacement for propylene glycol.

Both TEA and propylene glycol are good solvents for many photo chemicals.

However, when TEA is mixed with water it forms a basic solution (on the alkali side, with pH in the range of 9 to 10 depending on the relative amounts of TEA and Water). This feature of TEA makes it very useful with developers like PC-TEA and 510-Pyro.

Just add water to the concentrate and your working solution developer is ready to go.

Mix neutral pH water with Propylene Glycol and the resulting solution would be about pH neutral.

You could mix 510-Pyro in Propylene Glycol instead of TEA, but you would need to add some alkali (i.e. sodium carbonate, sodium hydroxide, sodium metaborate, etc., or TEA) to the working developer before you could develop film with it.

Tom Hoskinson · Feb 5, 2007

Jed Freudenthal said:
Tom, what are my subjective opinions, guesses and conjectures ? When I say there is no stain, there is no stain. You are saying there is stain, but do not mentione the level of stain. I cannot imagine what to add to the recipe/experiment, as described in the article at the APUG site 'high definition developers, staining and non-staining'. Nobody asked me for more clarification. And the formulas are in use for many years.
As you know, catechol 100% cannot exist, because it is degrading all the time. It would be an enormous analytical task to study the chemical reactions of propylene glycol with catechol and its degradation products as a function of time. And I certainly would not publish the results on the APUG site.
Over one century catechol has been put in the developer succesfully as a dry substance. A year or so ago, somebody came up with the idea to put it in propylene glycol. first. And now I have to proof that it gives problems:rolleyes:
I would say: you have to proof that it doesn't give problems.
I approached the design of the catechol (HD) formula in such way that it could stand the variations in catechol purity (natural degradation products). All one has to do with an 'old' catechol is to increase the amount of catechol. The strong point of this catechol HD developer is the simplicity. All there is: is a development agent and an alkali (with a very small amount of sudium sulfite).

Jed

Jed, I have not previously discussed stain in this thread. However, I have discussed stain in several other APUG threads and I usually determine the presence or absence of image stain by transmission densitometry of the processed film. Bleaching the silver from the image is another technique I sometimes use. See my Apug Gallery for an example graph showing image stain densities measured via color transmission densitometry.

I clearly stated in this thread that the catechol, pyrogallol, hydroquinone and phenidone stock solutions that I prepared by dissolving these reagents in propylene glycol, did not exhibit changes in color (over a period of 3 plus years) Periodic activity testing of these stock solutions DEMONSTRATED that no noticeable changes in developing reagent activity occured during the 3+ year period.

But, Thanks for your reply, Jed. While you did not reply directly to my questions, you did give me clues about why you saw changes in DEVELOPER COLOR AND ACTIVITY during your investigations.

It seems to me that you have been talking about color changes and possible DEVELOPING AGENT activity changes that you've observed in your Catechol based DEVELOPER SOLUTIONS; and NOT IN DEVELOPING REAGENT STOCK SOLUTIONS.

You stated: "The strong point of this catechol HD developer is the simplicity." "All there is: is a development agent and an alkali (with a very small amount of sudium sulfite)."

Jed, if you add water to your list of ingredients, and choose catechol as the developing agent; the list would include catechol, sodium sulfite and water.

This is a recipe for a very simple developing solution.

I would expect catechol aging reactions to begin immediately upon mixing this solution.

Adding additional alkali to the solution would make it more active - and make it age more rapidly.

mikebarger · Feb 5, 2007

Thanks Tom

Appreciate the help.

MIke

Jed Freudenthal · Feb 6, 2007

Tom Hoskinson said:
Jed, I have not previously discussed stain in this thread. However, I have discussed stain in several other APUG threads and I usually determine the presence or absence of image stain by transmission densitometry of the processed film. Bleaching the silver from the image is another technique I sometimes use. See my Apug Gallery for an example graph showing image stain densities measured via color transmission densitometry.

I clearly stated in this thread that the catechol, pyrogallol, hydroquinone and phenidone stock solutions that I prepared by dissolving these reagents in propylene glycol, did not exhibit changes in color (over a period of 3 plus years) Periodic activity testing of these stock solutions DEMONSTRATED that no noticeable changes in developing reagent activity occured during the 3+ year period.

But, Thanks for your reply, Jed. While you did not reply directly to my questions, you did give me clues about why you saw changes in DEVELOPER COLOR AND ACTIVITY during your investigations.

It seems to me that you have been talking about color changes and possible DEVELOPING AGENT activity changes that you've observed in your Catechol based DEVELOPER SOLUTIONS; and NOT IN DEVELOPING REAGENT STOCK SOLUTIONS.

You stated: "The strong point of this catechol HD developer is the simplicity." "All there is: is a development agent and an alkali (with a very small amount of sudium sulfite)."

Jed, if you add water to your list of ingredients, and choose catechol as the developing agent; the list would include catechol, sodium sulfite and water.

This is a recipe for a very simple developing solution.

I would expect catechol aging reactions to begin immediately upon mixing this solution.

Adding additional alkali to the solution would make it more active - and make it age more rapidly.

Hello Tom,
We discussed the presence of stain in the (my HD) catechol developer before. I said: there is no stain in the HD catechol developer ( or, if there is stain, it is not significant). You are using densitometric measurements to proof the presence of stain. I am using visual and microscopic inspection to support my statement. I experienced difficulties in the interpretation of the densitometric measurements because of the variety of the different stains. [In the case of the HD pyrogallol developer the reproducibility of the general stain was controlled in a photographic way, just to get rid of restrainer defects].

But now back to the catechol. Catechol is a wonderful substance because of the fine grain, no fog and no stain. This is the reason the developer formula can be very simple. No restrainer required. No stain is required to mask the fine grain. There is one disadvantage: it will degrade over time. Not fast, but it will degrade over the years.

Once the catechol is mixed with water it remains stable; when you wait 10 minutes adding the alkali, no problem. Once you add the alkali, I usually start the development process and will get very reproducible results. Other people using the developer have the same experience; and what is more important, I do not get people reporting problems. ( bad news travels fast). The degradation of catechol in the alkaline environment is not really fast. One could do a second development session in the same developer, but I do not advise that practice because the activity is down for sure.

Now the color changes I observe: dry catechol is white when it is fresh, almost black when it is 70 years old. After a few years it is light brown, has a lower activity than the fresh catechol, but can be used in developers.

When the 1.4 g catechol is dissolved in 800 ml water, there is no color change. When the alkali ( potassium carbonate) is added, the color is very light gray. After the development process the color change is usually determined by the paint of the anti halo layer, but there are film types with virtually no color change. That observation tells me, that if there is a degradation, it will not affect the color.
But, whatever happens, I am not using that used developer anymore.
[ This in contrast with my HD pyrogallol developer, where I use the used developer to make a reproducible general stain].

Jed

sanking · Feb 6, 2007

Jed,

You write,

"I said: there is no stain in the HD catechol developer ( or, if there is stain, it is not significant). You are using densitometric measurements to proof the presence of stain. I am using visual and microscopic inspection to support my statement."

Visual inspection is not a reliable method of proving or disproving the presence of stain in a stained negative. The stain can look very neutral to the eye. To measure stain you need a densitometer with a Blue mode (for silver papers) or a UV mode ( for alternative processes). In my experience pyrocatechin is always a staining developer when used in a simple formula with no ascorbic or sulfite. A very small amount of either ascorbic or sulfite will kill the stain, however.

As for the issue of pyrocatechin degrading in a propylene glycol solution, I agree with Tom that it does not happen. I have tested this with 5% pyrocatechin solutions, one mixed in water and the other mixed in glycol as a stronger solutions and then diluted to 5% with water. There was no (that is 0%) difference in activity in negatives exposed and developed identically immediately after mixing and one week later. Of course, I used a fresh batch of pyrocatechin, light beige in color, for the test. I have also used very old (2+ years old or more) solutions of pyrocatechin mixed in glycol and have observed no loss of activity in the reducer when compared to newly mixed solutions.

The tests to measure any degradation that would result in a loss of activity are relatively simple so I suggest others test for themselves. Not much point in continuing to discuss a difference of opinion when testing can resolve the issue so easily.

Sandy King

gainer · Feb 7, 2007

Whether there is a stain image that is visible to the eye is immaterial. A simple test of the kind of stain we want is to make prints on both VC paper and graded paper. The print on graded paper will show higher contrast. The overall stain that can be produced by the used PMK developer is contrast-reducing for VC paper and exposure increasing for graded paper. It causes the film base to be colored. A proper stain will be almost invisible to the eye, as it is proportional to the silver image. It is possible, however, to use Farmer's reducer to remove the silver image while leaving the stain image. You will be able to print this image by use of the highest grade of printing paper, or by a digital scan. Though not a very good print, it will show the presence or absence of a stain image. You will see if there is or is not a stain image if you view the bleached image through the blue color separation filter.

As to changes over such short periods of time after dissolving in glycol, I can only surmise there must have been some impurity in the glycol. Sufficient water content would probably do it. The Kodak HC110 developer uses the non-ionizing property of one of the glycols in the syrupy liquid to make it last for years without change. My initial experiments were with ethylene glycol based automobile antifreeze, which most certainly is not pure glycol, but I saw no such changes in activity as you have reported.

If water content is a problem, it should be reduced or eliminated by distilling off the water vapor. Propylene glycol boils at a much higher temperature than water.

Jed Freudenthal · Feb 7, 2007

sanking said:
Jed,

You write,

"I said: there is no stain in the HD catechol developer ( or, if there is stain, it is not significant). You are using densitometric measurements to proof the presence of stain. I am using visual and microscopic inspection to support my statement."

Visual inspection is not a reliable method of proving or disproving the presence of stain in a stained negative. The stain can look very neutral to the eye. To measure stain you need a densitometer with a Blue mode (for silver papers) or a UV mode ( for alternative processes). In my experience pyrocatechin is always a staining developer when used in a simple formula with no ascorbic or sulfite. A very small amount of either ascorbic or sulfite will kill the stain, however.

As for the issue of pyrocatechin degrading in a propylene glycol solution, I agree with Tom that it does not happen. I have tested this with 5% pyrocatechin solutions, one mixed in water and the other mixed in glycol as a stronger solutions and then diluted to 5% with water. There was no (that is 0%) difference in activity in negatives exposed and developed identically immediately after mixing and one week later. Of course, I used a fresh batch of pyrocatechin, light beige in color, for the test. I have also used very old (2+ years old or more) solutions of pyrocatechin mixed in glycol and have observed no loss of activity in the reducer when compared to newly mixed solutions.

The tests to measure any degradation that would result in a loss of activity are relatively simple so I suggest others test for themselves. Not much point in continuing to discuss a difference of opinion when testing can resolve the issue so easily.

Sandy King

Sandy, as you know, I added a small amount of sulfite ( for another reason) in my catechol HD developer. So, your statement that there is no stain is in agreement with my observation. And, I consider it as an advantage to have no stain ( better definition in the higher spatial frequencies). Because the grain is fine enough and there is no restrainer with catechol, it is possible to leave the stain out.
But, if there are people who like the stain with catechol, they do so. I introduced that situation in the pyrogallol HD developer. With the pyrogallol HD developer I use the stain(s) to mask the grain and the effects of the restrainer.

From my own and from other experience, I know one has to be careful with the interpretation of the data of a (micro) densitometer. If filters are used, one can detect the presence of colored light. But it is hard to say what the origin of the colorization is. With catechol one starts with a colorization of the silver image, which is no stain. Therefore, any densitometric determination has to be done with care.

I can imagine that propylene glycol is a stable solvent for fresh (non-degraded) catechol. I did my experiments with a 'practical' partially degraded catechol. And one might see the results of interactions with the degradation products of catechol. When I saw the effects with the partially degraded catechol, I decided: I better follow the road that has been followed for a very long time: mix the catechol dry. The earliest publication I have on the subject is from around 1895. The reason that pyrogallol has been used instead is the price. The reason that pyrogallol lost ground in the 1930's was the economic situation at that time.

Jed

Jed Freudenthal · Feb 7, 2007

gainer said:
Whether there is a stain image that is visible to the eye is immaterial. A simple test of the kind of stain we want is to make prints on both VC paper and graded paper. The print on graded paper will show higher contrast. The overall stain that can be produced by the used PMK developer is contrast-reducing for VC paper and exposure increasing for graded paper. It causes the film base to be colored. A proper stain will be almost invisible to the eye, as it is proportional to the silver image. It is possible, however, to use Farmer's reducer to remove the silver image while leaving the stain image. You will be able to print this image by use of the highest grade of printing paper, or by a digital scan. Though not a very good print, it will show the presence or absence of a stain image. You will see if there is or is not a stain image if you view the bleached image through the blue color separation filter.

As to changes over such short periods of time after dissolving in glycol, I can only surmise there must have been some impurity in the glycol. Sufficient water content would probably do it. The Kodak HC110 developer uses the non-ionizing property of Ione of the glycols in the syrupy liquid to make it last for years without change. My initial experiments were with ethylene glycol based automobile antifreeze, which most certainly is not pure glycol, but I saw no such changes in activity as you have reported.

If water content is a problem, it should be reduced or eliminated by distilling off the water vapor. Propylene glycol boils at a much higher temperature than water.

I made prints on both VC and graded paper. Because the two papers are so different, one can hardly draw any conclusion on the differences one can see in the prints from catechol HD negatives.
In the case with pyrogallol HD negatives (with stain) the difference is that much, . that one can see the influence of the stain in the quality of the print ( in the highlights in particular).

Jed

gainer · Feb 7, 2007

Still, it would be instructional to bleach out the silver image to see what remains. Use a test negative, of course, because the silver image cannot be restored. If I remember correctly, pyrogallol and hydroquinone stains are more visible than catechol stain. The color produced by warm tone developers is due to grain size and will not remain after bleaching. If you are partial to the pyrogallol stain, you can substitute pyrogallol for catechol weight for weight in the formula for Pyrocat MC. The molecular weight of pyrogallol is greater than that of catechol but there are three OH groups in pyrogallol and only 2 in catechol.

I have found that triethanolamine works well with the PMK "A" solution as an activator when used in the same amount (by volume) as the usual metaborate solution. This fact combined with the admitted longevity of PMK "A" makes it very convenient to use if the PMK stain is what you want. That is true only if you have a good supply of TEA.

Jed Freudenthal · Feb 8, 2007

gainer said:
Still, it would be instructional to bleach out the silver image to see what remains. Use a test negative, of course, because the silver image cannot be restored. If I remember correctly, pyrogallol and hydroquinone stains are more visible than catechol stain. The color produced by warm tone developers is due to grain size and will not remain after bleaching. If you are partial to the pyrogallol stain, you can substitute pyrogallol for catechol weight for weight in the formula for Pyrocat MC. The molecular weight of pyrogallol is greater than that of catechol but there are three OH groups in pyrogallol and only 2 in catechol.

I use either the catechol HD developer or the pyrogallol HD developer. Thecatechol HD has no stain, the pyrogallol HD has stain ( refer to the artcle 'high definition developers, staining and non-staining). I am not using pyrocat (MC). As you indicate, the warm color of the catechol developer is due to grain size. There are warm tone paper developers also based on catechol.
In the bleaching test, you recommend, the assumption is that the stain will be stable in the bleaching process. One doesn't know. Therefore I test it in a microscopic inspection. If there is a stain, the image will be somewhat blurred. If the color is due to grain size, the image of the grain will be sharp. My conclusion is based on such an inspection.
It is of course interesting what processes are going on. The most important fact is, that the print made from a catechol HD negative has a 'precise' appearance, and a print made from a pyrogallol HD negative is less precise, as a result of a blurring effect of the stain. It is a matter of tast what you prefer. The preference usually depends on the magnification factor of the print and the subject. A landscape on 16x20" is usually best ( via a panel) with catechol HD and a portait 12x16" is better with pyrogallol HD ( provided appropriate lenses are used).

Jed

gainer · Feb 8, 2007

My experience with the bleaching process is that the stain image will remain. If it does not appear then you may assume it was never there, but if it does appear, there is no other explanation for it than that it was a result of the development. It is well known that catechol and hydroquinone are both staining developers when sulfite is not present or is present in very small concentration. The colors of the stains produced by hydroquinone, catechol and pyrogallol are different.

My reference to Pyrocat MC was as a typical representative of the Pyrocat series, which includes the HD and PC variations. All use a very small amount of ascorbic acid in place of sodium sulfite along with metol, phenidone or p-aminophenol to activate the catechol. Catechol, phenidone, ascorbic acid and p-aminohenol base are soluble in propylene or ethylene glycol. Metol requires a small amount of TEA and water to free the base, as the hydrogen sulfate part of Metol is not soluble in the glycols.

I am not familiar with the formulas you refer to as catechol HD and pyrogallol HD. I would appreciate it if you would elucidate so we can have common ground for "battle."

gainer · Feb 8, 2007

P.S.
There are non-catechol developers that produce warm tones of film or paper. A bleach test will prove that either the warm tone is due to stain, in which case the dye image remains, or due to grain size.

Jed Freudenthal · Feb 8, 2007

gainer said:
My experience with the bleaching process is that the stain image will remain. If it does not appear then you may assume it was never there, but if it does appear, there is no other explanation for it than that it was a result of the development. It is well known that catechol and hydroquinone are both staining developers when sulfite is not present or is present in very small concentration. The colors of the stains produced by hydroquinone, catechol and pyrogallol are different.

My reference to Pyrocat MC was as a typical representative of the Pyrocat series, which includes the HD and PC variations. All use a very small amount of ascorbic acid in place of sodium sulfite along with metol, phenidone or p-aminophenol to activate the catechol. Catechol, phenidone, ascorbic acid and p-aminohenol base are soluble in propylene or ethylene glycol. Metol requires a small amount of TEA and water to free the base, as the hydrogen sulfate part of Metol is not soluble in the glycols.

I am not familiar with the formulas you refer to as catechol HD and pyrogallol HD. I would appreciate it if you would elucidate so we can have common ground for "battle."

Hi Gadget:
The formulas I refer to were published on the APUG site under ' high definition developers staining and non-staining' in the 'staining section. Sean republished them after the reorganization of the APUG site, but not under the original date and not under my name I informed Sean to correct that. Unfortunately, he did not correct the date up to now.
I hope, you can find the old stuff on the APUG site. You cannot find it anymore via a search machine like Google. I also informed Sean to make the APUG site transparent again.

The developers I published on the APUG site are 'modifications' of classical formulas. I modified them to remove existing problems. Let me know whether you can find the formulas I published before. I hope Sean will make the APUG site transparent again. The pyrogallol HD formulas are now tested for about 10 years; the catechol HD formulas are tested for 5 years ( by many people).

There are many appearances of stains. I have no information whether they are all resistant against bleaching. There is an extensive literature on this; however, it is quite a job to go through all that. Therefore, I stick to the old procedure of microscopic inspection.

Jed

Tom Hoskinson · Feb 8, 2007

Jed Freudenthal said:
...Therefore, I stick to the old procedure of microscopic inspection...

Jed

Jed, Pat Gainer, Sandy King and I have all previously explained to you why visual inspection is not an effective method of determining whether image stain is present, post development.

Microscopic inspection is a form of visual inspection and is not an appropriate
tool for establishing the presence or absence of image stain.

If image stain is present, the stain will remain after the film is bleached.

To bleach the film, I use a simple bleach made of potassium ferricyanide, potassium bromide and water.

The film can then be redeveloped, if desired.

See this thread: (there was a url link here which no longer exists)

Pyrocathecol, catechol age

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