tanning, not staining - catechol.

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el wacho

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hi,

are there any film developers that rely only on the tanning aspect of catechol and not its staining property? thanks
 

sanking

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hi,

are there any film developers that rely only on the tanning aspect of catechol and not its staining property? thanks

You can take any pyrocatechol based developer that stains, say Pyrocat-HD or Pyrocat-MC, and increase the amount of sulfite in the formula by about 5X-10X, and you will have a tanning but not staining developer.

I described such a developer some years ago on the AZO forum and called it, as I recall, Pyrocat+. The reason for the + is that the extra sulfite adds a very high amount of energy to the formula so that development times for the same CI are much shorter than with the regular Pyrocat formula.

Sandy King
 
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el wacho

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thank you Sandy,

can i infer from your statement that increasing the sodium metabisulfite upto 4x won't affect the staining properties?
 

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thank you Sandy,

can i infer from your statement that increasing the sodium metabisulfite upto 4x won't affect the staining properties?

I think 2X the amount of metabisulfite would not affect the staining properties, but 4X probably would.

Some years ago I tested the effect of additional metabisulfite in the formula at several levels but unfortunately I lost the notes and no longer have the data. But my recollection is that over 5X the amount will give a decided difference in results as regards the intensity of the stain. And of course the developer will become much more active.

Sandy King

Sandy
 
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el wacho

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thanks Sandy,

so does sod. metabisulfite increase development as it is increased? i thought it was acidic. anyway thanks again!
 

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Sulfite or metabisulfite, bisulfite that is.
What's it going to be? Dan

Not really much of a distinction for this purpose. One mole of bisulfite in the stock solution makes 1 mole of sulfiite when it is dissolved in water to make a working Pyrocat-HD solution. One mole of metabisulfite makes 2 moles of sulfite when dissolved in water to make the working solution.

Most chemicals sold as sodium bisulfite are in fact a mixture of bisulfite and metabisulfite, or pure metabisulfite. Pure sodium bisulfite in powder form is rare unless you buy analytical reagent grade. I specify sodium metabisulfite for mixing the Pyrocat-HD stock solution A.

Sandy King
 
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ilya1963

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But what is a benefit of tanning vs.. staining ? wouldn't it have similar result in the end when printing?


IA
 

sanking

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But what is a benefit of tanning vs.. staining ? wouldn't it have similar result in the end when printing?


IA

Not necessarily. Staining adds a dye that increases contrast. Tanning prevents development spread and increases resolution. A tanning but not staining developer might be preferred in some cases.

Sandy King
 

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this stopping of development spread IMO is one of the greatest attribute of a tanning dev.
Its what sold me on pyro in the first place.
Sandy could you go further into the way a tanning dev stops the spread , I think that this is the most underrated aspect of pyro.
Not necessarily. Staining adds a dye that increases contrast. Tanning prevents development spread and increases resolution. A tanning but not staining developer might be preferred in some cases.

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sanking

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this stopping of development spread IMO is one of the greatest attribute of a tanning dev.
Its what sold me on pyro in the first place.
Sandy could you go further into the way a tanning dev stops the spread , I think that this is the most underrated aspect of pyro.

With a tanning developer there is very little migration of silver halide during development because early in development a hard relief image is formed. This results in more precise reduction that minimizes infectious development (spreading of silver development beyond the exact image boundaries).

You can see the result if you make two negatives of a strongly back lighted scene, say a tree in the winter with no leaves against the sun. Develop one of the negative in a traditional developer, the other in a pyro type developer (PMK, Pyrocat, etc.) and compare the results. Chances are there will be a lot less infectious development with the pyro developed negative.

Some years ago I carried out some resolution tests comparing two pyro type developers (PMK and Pyrocat-HD) with two traditional developers (D76 and Xtol). With every film tested the pyro developers gave about 15% higher resolution. The statement that Pyro developers are sharper is not a myth, but a fact that can be tested and proven.

Sandy King
 
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Bob Carnie

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Thanks Sandy

In a nutshell I think this is what makes the pyro devs rock.


With a tanning developer there is very little migration of silver halide during development because early in development a hard relief image is formed. This results in more precise reduction that minimizes infectious development (spreading of silver development beyond the exact image boundaries).

You can see the result if you make two negatives of a strongly back lighted scene, say a tree in the winter with no leaves against the sun. Develop one of the negative in a traditional developer, the other in a pyro type developer (PMK, Pyrocat, etc.) and compare the results. Chances are there will be a lot less infectious development with the pyro developed negative.

Some years ago I carried out some resolution tests comparing two pyro type developers (PMK and Pyrocat-HD) with two traditional developers (D76 and Xtol). With every film tested the pyro developers gave about 15% higher resolution. The statement that Pyro developers are sharper is not a myth, but a fact that can be tested and proven.

Sandy King
 

dancqu

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Matters Little?

Not really much of a distinction for this purpose. Sandy King

Your post 2 this thread mentions upping the sulfite by 5 - 10
times. The result a tan rather than a stain. And it matter
little if it be sulfite or bisulfite? Dan
 

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Your post 2 this thread mentions upping the sulfite by 5 - 10
times. The result a tan rather than a stain. And it matter
little if it be sulfite or bisulfite? Dan

That is correct. It does not matter if you increase the amount of sodium bisulfite in the stock solution by 5X or increase the amount of sulfite in the working solution by 5X. Both methods give the same amout of sulfite in the working solution because one mole of bisulfite in the stock will become one mole of sulfite in the working solution when the stock is diluted with water.

Sodium bisulfite or sodium metabisulfite is used in the stock solution as a preservative, but when a stock solution containing either is mixed with water to form a working solution the bisulfite or metabisulfite is converted to sulfite, one mole of bisulfite to one mole of sulfite, one mole of metabisulfite to two moles of sulfite.

Sandy King
 
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el wacho

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do the rules change in two bath development? for example,

bath A

Metol 2.5g
Sodium Metabisulfite 10g
Pyrocatechin 5g
Water to make 1 litre


bath B

sodium hydroxide 10 g
water to make 1 litre.

do you think that it will stain because of the low amount of bisulfite absorbed into the gelatine? i've used your ratio of bisulfite/water assuming that you found a balance between enough bisulfite to prevent oxidation but not enough to interfere with the formation of the stain. obviously, one of my driving interests with this formula variation of your pyrocat m is to extend the longetivity of bath A. your thoughts are much appreciated Sandy.
 
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sanking

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do the rules change in two bath development? for example,

bath A

Metol 2.5g
Sodium Metabisulfite 10g
Pyrocatechin 5g
Water to make 1 litre


bath B

sodium hydroxide 10 g
water to make 1 litre.

do you think that it will stain because of the low amount of bisulfite absorbed into the gelatine? i've used your ratio of bisulfite/water assuming that you found a balance between enough bisulfite to prevent oxidation but not enough to interfere with the formation of the stain. obviously, one of my driving interests with this formula variation of your pyrocat m is to extend the longetivity of bath A. your thoughts are much appreciated Sandy.


Interesting path you are taking. I had not previously considered increasing the amount of metabisulfite to extend the longevity of working bath A but it is an idea that certainly deserves some testing. I understand why you are going with this now. However, there is another problem if you are planning to attempt to save the working solution for several days. Once the metabisulfite is converted to sulfite in the working solution it will probably start to break down as does the B solution of the Pyro ABC formula which uses a sulfite solution in water as the B stock. I can not say for sure how long it will take the sulfite to break down in a 1:10 working Pyrocat-HD solution but you could run a quality control test at Day one, Day 7, and Day 14 and 28 to check it.

Anyway, I guess there are two main questions. The first is how much suilfite is too much such that it kills the stain? And the second, once the correct amount of sulfite is determined, how long will it preserve a working solution? I am going to suggest a maximum of about 5X the amount of sulfite.

Sandy King
 

dancqu

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No Conversion

... bisulfite in the stock will become one mole of sulfite in the
working solution when the stock is diluted with water.

... when a stock solution containing either is mixed with water
to form a working solution the bisulfite or metabisulfite is
converted to sulfite, one mole of bisulfite to one mole of
sulfite, one mole of metabisulfite to two moles of sulfite.

Simply adding water will not convert a bisufite into a sulfite.
A bisulfite is an acid salt where a sulfite is a normal salt;
in this case both are salts of sodium.

As for sodium metabisulfite and it's conversion to sodium
bisulfite: Na2S2O5 + H2O > 2(NaHSO3).

The normal salt is mildly alkaline, about ph 10, while the
acid salt is mildly acidic, about ph 4 Dan
 

sanking

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Sodium bisulfite will convert to sulfite with an adjustment of pH. This will certainly take place in mixing a working Pyroat-HD solution, where the pH is close to 12.0.

However, as noted earlier, I don't recommend sodium bisulfite for the Pyrocat-HD stock solutions, but sodium metabisulfite. So to go back to my original response to El Wacho, I suggested that the Pyrocat-HD working solution would kill the stain if 5X-10X sulfite was added. So we could get there by adding 5X sodium metabisulfite to the stock solution, or 10x sulfite directly to the working solution.

Sandy King



Simply adding water will not convert a bisufite into a sulfite.
A bisulfite is an acid salt where a sulfite is a normal salt;
in this case both are salts of sodium.

As for sodium metabisulfite and it's conversion to sodium
bisulfite: Na2S2O5 + H2O > 2(NaHSO3).

The normal salt is mildly alkaline, about ph 10, while the
acid salt is mildly acidic, about ph 4 Dan
 

ilya1963

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Sorry for being ignorant:


So we could get there by adding 5X sodium metabisulfite to the stock solution, or 10x sulfite directly to the working solution.

Sandy King

Working solution? as an A+B+water? Dump 10x bisulfite in it and develop?how many times can you work with this working solution?

Would the developing times be cut in half, what would you recommend for a starting point? would it still be fine for DBI without the stain , but with tan?

I can not say for sure how long it will take the sulfite to break down in a 1:10 working Pyrocat-HD solution but you could run a quality control test at Day one, Day 7, and Day 14 and 28 to check it.

Anyway, I guess there are two main questions. The first is how much sulfite is too much such that it kills the stain? And the second, once the correct amount of sulfite is determined, how long will it preserve a working solution? I am going to suggest a maximum of about 5X the amount of sulfite.

Sandy King

If you were working with PyrocatHD with this additional bisulfite , say 4 batches(10sheets each) of film ,could you possibly use same working solution for all 4 batches ?
I would not care to keep working solution for a week at a time , but it would be handy and less wasteful if it could be reused in a matter of a few hours


Thank you.

IA
 

sanking

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I can not answer the questions about adding extra sulfite to working solution A with two bath development. My comments were offered as suggestion but have not been tested.

However, if the goal is to re-use the working solution A for three or more times during a window of an hour or two no additional sulfite is needed. I do this routinely in developing eight rolls of 120 film two rolls at a time.

Sandy King



Sorry for being ignorant:




Working solution? as an A+B+water? Dump 10x bisulfite in it and develop?how many times can you work with this working solution?

Would the developing times be cut in half, what would you recommend for a starting point? would it still be fine for DBI without the stain , but with tan?



If you were working with PyrocatHD with this additional bisulfite , say 4 batches(10sheets each) of film ,could you possibly use same working solution for all 4 batches ?
I would not care to keep working solution for a week at a time , but it would be handy and less wasteful if it could be reused in a matter of a few hours


Thank you.

IA
 
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el wacho

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no , all of my comments have been around two bath development and extending the preservation of bath A.
 
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