Pyrocathecol, catechol age

gainer · Feb 12, 2007

The only experimental evidence missing from Tom Hoskinson's statement is what remains of the warm toned image from Microdl-X development after bleaching. Your comment should have been based on a simple test, not on conjecture that perhaps the warm part of the image will remain after bleaching.

Any scientific background should include lessons in and practice of the scientific method. It is a proven fact that any system of axioms at least as rich as arithmetic is either incomplete or inconsistent or both. We cannot prove a theory. Our best bet is to try our best to disprove it. Instaed of searching for experimental proof that a theory is true, we must search for experimental evidence that for at least one case it is not true. Every case where the theory is applicable broadens the range of practical use of the theory. In other words, the scientist attacks his own theories with a vengeance. Part of your attack on your own theory should have been to bleach a Microdol X image to see what actually remains.

Can we say that a single-agent developer always minimizes or eliminates edge effects? I think not. Any experiment aimed at finding the controlling factors of edge effects must be a multivariate one with developer composition, concentration, agitation technique and other factors.

Now, if your purpose is only to correlate microscopic evidence of edge effect with subjective evaluation, be careful what you ask the subjective evaluators to do.

Tom Hoskinson · Feb 12, 2007

Jed Freudenthal said:
With respect to the book of Haist: I can only find stuff on tanning, but nothing on staining. I can agree with the stuff on tanning. But the subject now is staining.

Jed

Jed, emulsion gelatin tanning and staining are closely related topics. Your response tells me that you did not read all of Haist's Tanning Developer Section, which begins on page 507 and continues through page 538 of Volume I, Modern Photographic Processing.

In particular, please read page 516 on the degree of gelatin tanning formation, which states in part:

"...The departure from a constant relationship of relief and silver is probably attributable to side reactions such as stain formation in which the oxidation products are not wholly utilized in combining with gelatin."

"Stain image formation is distinct from the formation of a tanned relief image. Stain results from two or more developer molecules reacting together in an oxidizing medium to yield a colored, insoluble product that is retained, imagewise in the gelatin. Sodium Sulfite inhibits staining, except incompletely in the case of pyrogallol developers, by combining with the oxidation products, but gelatin tanning is inhibited. Gelatin tanning occurs when the oxidized developer molecule reacts with a gelatin molecule in an oxidizing medium..."

Jed Freudenthal · Feb 13, 2007

Tom Hoskinson said:
Jed, emulsion gelatin tanning and staining are closely related topics. Your response tells me that you did not read all of Haist's Tanning Developer Section, which begins on page 507 and continues through page 538 of Volume I, Modern Photographic Processing.

In particular, please read page 516 on the degree of gelatin tanning formation, which states in part:

"...The departure from a constant relationship of relief and silver is probably attributable to side reactions such as stain formation in which the oxidation products are not wholly utilized in combining with gelatin."

"Stain image formation is distinct from the formation of a tanned relief image. Stain results from two or more developer molecules reacting together in an oxidizing medium to yield a colored, insoluble product that is retained, imagewise in the gelatin. Sodium Sulfite inhibits staining, except incompletely in the case of pyrogallol developers, by combining with the oxidation products, but gelatin tanning is inhibited. Gelatin tanning occurs when the oxidized developer molecule reacts with a gelatin molecule in an oxidizing medium..."

Tom, You are quoting Haist p.516. He describes the formation of stain in this quotation. Then he says Sodium Sulfite inhibits staining, except incompletely in the case of pyrogallol developers. Now, I observe stain in the pyrogallol developer and 'no' stain in the catechol developer. Both have sulfite in them, like the Hans Windisch developer. I would say that Haist is supporting the observation, although not explicitly, like 'there is no stain in catechol developers with sulfite in them'. Unfortunately there is no reference to the statement.

I think Haist is referring to developers with one developing agent, because he calls pyrogallol an exception. If there are more developing agents in a developer, there is a greater chance to have a stain. And, there are many formulas around with more than one developing agent. There one might expect stain more readily.

Jed

sanking · Feb 13, 2007

Jed Freudenthal said:
Tom, You are quoting Haist p.516. He describes the formation of stain in this quotation. Then he says Sodium Sulfite inhibits staining, except incompletely in the case of pyrogallol developers. Now, I observe stain in the pyrogallol developer and 'no' stain in the catechol developer. Both have sulfite in them, like the Hans Windisch developer. I would say that Haist is supporting the observation, although not explicitly, like 'there is no stain in catechol developers with sulfite in them'. Unfortunately there is no reference to the statement.

I think Haist is referring to developers with one developing agent, because he calls pyrogallol an exception. If there are more developing agents in a developer, there is a greater chance to have a stain. And, there are many formulas around with more than one developing agent. There one might expect stain more readily.

Jed

Jed,

It is not correct that pyrocatechin developers with sulfite will not stain. They will stain if the amount of sulfite level is not too high. However, if the sulfite level reaches a certain point, there will be no stain at all. Also, having experimented with pyrocatechin developers for a very long time, which has involved evaluating stain density in a variety of ways, including bleaching, I know for certain that there is a color density that remains in the negative after bleaching. I am reasonably confident (about 99.9% sure) that this is stain density, not a color caused by the size of the grains. If the latter were true, bleaching would not reduce the density. Why not just do the test yourself instead of quoting more studies? If you measure the negative first in Green, Blue and UV light, then bleach the negative, then re-measure with the same light, you will have the answer.

Also, with regard to your statement, "if there are more developing agents in a developer, there is a greater chance to have a stain," I belive that this is wrong. It may have applied to one specific test that that for some reason you picked up on, but it is wrong as a general statement. I have done numerous tests varying the amount of metol, p-aminophenol and phenidone in pyrocatechin developers (with no-sulfite, or very low sulfite), and in every experiment the intensity of the stain image is greatest when pyrocatechin is the sole developer, and decreases steadily as the amount of the other reducers is increased. From the results of these experiments I must coclude that the notion that more developing agent increase the chance of staining in low-sulfite pyrocatechin developers is just plain wrong as a general rule. In fact, my empirical data suggests that the very opposite is true, i.e. the addition of a secondary reducer **decreases** the intensity of the stain. But you don't have to take my word for this. Just do the tests yourself and see what happens. Start with a 100% pyrocatechin developer, develop a step wedge negative and measure the stain, bleach, and then re-measure the stain. Repeat the test with varying amounts of a secondary reducer, say phenidone, metol and p-aminophenol.

Sandy King

Tom Hoskinson · Feb 13, 2007

sanking said:
Jed,

It is not correct that pyrocatechin developers with sulfite will not stain. They will stain if the amount of sulfite level is not too high. However, if the sulfite level reaches a certain point, there will be no stain at all. Also, having experimented with pyrocatechin developers for a very long time, which has involved evaluating stain density in a variety of ways, including bleaching, I know for certain that there is a color density that remains in the negative after bleaching. I am reasonably confident (about 99.9% sure) that this is stain density, not a color caused by the size of the grains. If the latter were true, bleaching would not reduce the density. Why not just do the test yourself instead of quoting more studies? If you measure the negative first in Green, Blue and UV light, then bleach the negative, then re-measure with the same light, you will have the answer.

Also, with regard to your statement, "if there are more developing agents in a developer, there is a greater chance to have a stain," I belive that this is wrong. It may have applied to one specific test that that for some reason you picked up on, but it is wrong as a general statement. I have done numerous tests varying the amount of metol, p-aminophenol and phenidone in pyrocatechin developers (with no-sulfite, or very low sulfite), and in every experiment the intensity of the stain image is greatest when pyrocatechin is the sole developer, and decreases steadily as the amount of the other reducers is increased. From the results of these experiments I must coclude that the notion that more developing agent increase the chance of staining in low-sulfite pyrocatechin developers is just plain wrong in my cases. In fact, my empirical data suggests that the very opposite is true, i.e. the addition of a secondary reducer **decreases** the intensity of the stain. But you don't have to take my word for this. Just do the tests yourself and see what happens. Start with a 100% pyrocatechin developer, develop a step wedge negative and measure the stain, bleach, and then re-measure the stain. Repeat the test with varying amounts of a secondary reducer, say phenidone, metol and p-aminophenol.

Sandy King

Excellent response, Sandy!

Jed, please read Sandy's response carefully. I strongly recommend that you perform the testing Sandy describes in his last paragraph.

Jed Freudenthal · Feb 13, 2007

sanking said:
Jed,

It is not correct that pyrocatechin developers with sulfite will not stain. They will stain if the amount of sulfite level is not too high. However, if the sulfite level reaches a certain point, there will be no stain at all. Also, having experimented with pyrocatechin developers for a very long time, which has involved evaluating stain density in a variety of ways, including bleaching, I know for certain that there is a color density that remains in the negative after bleaching. I am reasonably confident (about 99.9% sure) that this is stain density, not a color caused by the size of the grains. If the latter were true, bleaching would not reduce the density. Why not just do the test yourself instead of quoting more studies? If you measure the negative first in Green, Blue and UV light, then bleach the negative, then re-measure with the same light, you will have the answer.

Also, with regard to your statement, "if there are more developing agents in a developer, there is a greater chance to have a stain," I belive that this is wrong. It may have applied to one specific test that that for some reason you picked up on, but it is wrong as a general statement. I have done numerous tests varying the amount of metol, p-aminophenol and phenidone in pyrocatechin developers (with no-sulfite, or very low sulfite), and in every experiment the intensity of the stain image is greatest when pyrocatechin is the sole developer, and decreases steadily as the amount of the other reducers is increased. From the results of these experiments I must coclude that the notion that more developing agent increase the chance of staining in low-sulfite pyrocatechin developers is just plain wrong as a general rule. In fact, my empirical data suggests that the very opposite is true, i.e. the addition of a secondary reducer **decreases** the intensity of the stain. But you don't have to take my word for this. Just do the tests yourself and see what happens. Start with a 100% pyrocatechin developer, develop a step wedge negative and measure the stain, bleach, and then re-measure the stain. Repeat the test with varying amounts of a secondary reducer, say phenidone, metol and p-aminophenol.

Sandy King

Sandy, your starting point is a developer which has stain, which has adjacency effects. My starting point is just the other way around. You can imagine that I am not really interested in the experiments to get stain. Another thing is that all the experiments has been done, but with the objective to get rid of the irreproducible stain and the adjacency effects ( for mainly scientific purposes).
Before my retirement, I was head of the analytical chemistry division of the national Institutes of health and environment ( 1700 people) working for the Dutch governement but for the European Commision and for world organizations as the WHO al well. Within this division there was a department for (scientific) photography. In this department all the testing etc. has been done in collaboration with the Agfa research laboratories and the english Kodak laboratories (what is Forte now). All the MTF's and everyting has been done. I think you might understand that I am not going to do any testing I am NOT after.
But, I would say: if your are happy with a stain and adjacency effects, OK. Our objectives are just different. And we are both happy with our developers.

Jed

sanking · Feb 13, 2007

Tom Hoskinson said:
Excellent response, Sandy!

Jed, please read Sandy's response carefully. I strongly recommend that you perform the testing Sandy describes in his last paragraph.

Tom,

Jed's last response convinced me of the futility of further direct exchange with him on this subject. I am assuming a linguistic problem based on the fact that we speak different native languages. For the record, however, here is what I know about the use of pyrocatechin, both in solutions, and of its use as a developer. I think this information needs to be on the record because, frankly, there has been a lot of misinformation, and if I may dare use such lanaguage, flat-out BS, presented in this thread.

Let me remark that all of my testing has been carried out with fresh pyrocatechin, white or beige in color. The reducing potential of pyrocatechin decreases with age and one should not expect the same results when testing with old pyrocatechin.

Conclusions

1. Pyrocatechin is for all practical purposes extremely stable in propylene glycol solutions. I have pyrocatechin/glycol solutions on hand that are 2.5 years or older, and they still work just as they did when mixed.

2. A simple developer that contains nothing other than pyrocatechin, in the amount of about 1-2g per liter of working developer, and potassium carbonate, produces a lot of stain.

3. If one adds sulfite to the simple pyrocatechin developer the stain will decrease in intensity, and if enough sulfite is added this developer will eventually become a non-staining developer. Relatively little sulfite is needed to make the developer non-staining, since pyrocatechin is much more sensitive to sulfite than pyrogallol.

4. If one adds ascorbic acid to the simple pyrocatechin developer the stain will decrease in intensity, and if enough ascorbic acid is added this developer will eventually become a non-staining developer. Very little ascorbic is needed to make the developer non-staining.

5. If one adds a secondary reducer to the simple pyrocatechin developer, say metol, phenidone, or p-aminophenol, the stain will becom less intense. The more of the secondary developer one adds, the less will be the stain. If you add enough of the secondary reducer, the stain will disappear altogether.

As you know, several years ago I modified the Pyrocat-HD formula by increasing the amount of sulfite in it to make it non-staining. This topic was discussed widely on the AZO forum.

If anyone has actual data from testing to disprove any of my findings I welcome it. But until such time as such data is presented, my own empirical data supports all of the conclusions listed above.

Sandy

Tom Hoskinson · Feb 13, 2007

sanking said:
Tom,

Jed's last response convinced me of the futility of further direct exchange with him on this subject. I am assuming a lingistic problem based on the fact that we speak differnet native languages. For the record, however, here is what I know about the use of pyrocatechin,both in solutions, and of its use as a developer. I think this information needs to be on the record because, frankly, there has been a lot of misinformation, and if I may dare use such lanaguage, flat-out BS, presented in this thread.

Let me remark that all of my testing has been carried out with fresh pyrocatechin, white or beige in color. The reducing potential of pyrocatechin decreases with age and one should not expect the same results when testing with old pyrocatechin.

Conclusions

1. Pyrocatechin is for all practical purposes extremely stable in propylene glycol solutions. I have pyrocatechin/glycol solutions on hand that are 2.5 years or older, and they still work just as they did when mixed.

2. A simple developer that contains nothing other than pyrocatechin, in the amount of about 1-2g per liter of working developer, and potassium carbonate, produces a lot of stain.

3. If one adds sulfite to the simple pyrocatechin developer the stain will decrease in intensity, and if enough sulfite is added this developer will eventually become a non-staining developer. Relatively little sulfite is needed to make the developer non-staining, since pyrocatechin is much more sensitive to sulfite than pyrogallol.

4. If one adds ascorbic acid to the simple pyrocatechin developer the stain will decrease in intensity, and if enough ascorbic acid is added this developer will eventually become a non-staining developer. Very little ascorbic is needed to make the developer non-staining.

5. If one adds a secondary reducer to the simple pyrocatechin developer, say metol, phenidone, or p-aminophenol, the stain will becom less intense. The more of the secondary developer one adds, the less will be the stain. If you add enough of the secondary reducer, the stain will disappear altogether.

As you know, several years ago I modified the Pyrocat-HD formula by increasing the amount of sulfite in it to make it non-staining. This topic was discussed widely on the AZO forum.

If anyone has actual data from testing to disprove any of my findings I welcome it. But until such time as such data is presented, my own empirical data supports all of the conclusions listed above.

Sandy

Sandy, my test data and my conclusions agree with yours.

Pyrocathecol, catechol age

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