Why Pyrol rather than hydroquinone?

[Kirk Keyes]

NER - did you know that XTOL generates a stain? It does, bleach some XTOL processed film and you will see a very faint magenta stain. It's not enough to have a significant effect, but it is visible.

 

[psvensson]

Kirk, he's going to ask you where you read that, so hit the books!

 

[NER]

Norman wrote:
"...I defer to Mees, Tull, Neblette, Hauff, Bogisch, Lumiere, Andresen, Haist and researchers of similar reputation whose reports were both authoritative and accurate, and did not - to the best of my current knowledge - mention anything about hydroquinone image stain. ..." My emphasis.

Before I quote something else, I'd just like to say two things:

-I'd trust the guys here who say that hydroquinone forms a stain image even if I didn't already know it, and

-few of the standard texts (or at least those I have) go into much detail on stain images, if they mention it at all, but they do cover tanning. Tanning and staining may not be the same, but they are similar, and if the developer oxidation product is coloured then there is likely to be a link between tanning and the formation of a stain image.

OK, so on to L P Clerc's Photography Theory and Practice, 1971 edition revised by R. E. Jacobson, Vol 4, Monochrome Processing:

"573. Oxidation Products of Developers; Tanning; Secondary Images.
The quinonoid oxidation products of developers that are formed in the absence of sulphite, or in the presence of very low concentration of sulphite, are deposited in the gelatine at the site of development, and in a quantity proportional to the amount of silver halide reduced. Usually they polymerize, giving rise to coloured, tanning substances of the nature of humic acids, whose exact constitution is unknown.

After removing the silver image ... a yellow or brown secondary image remains, which, though it may not appear very intense to the eye, can give acceptable prints on high contrast paper because of its absorbtion of actinic light. The following table (Lumière and Seyewetz, 1928) shows the colour of the secondary image obtained in various developers, its relative intensity and the concentration of sulphite necessary to prevent its formation.

Developer -- colour -- relative intensity -- sulphite g/litre

Pyro -- yellow-orange -- 10 -- 11
Catechol -- black -- 10 -- 6
Hydroquinone -- yellow-brown -- 10 -- 2
Chlorhydroquinone -- yellow-brown -- 10 -- 2
Amidol -- reddish-brown -- 8 -- 2
p-Aminophenol -- brownish-black -- 3 -- 2
Metol -- brownish-black -- 2 -- 1
PPD -- Grey -- 1 -- 0
Glycin -- None."


Best,
Helen

Thank you very much for the citation and quote.

 

[NER]

Kirk, he's going to ask you where you read that, so hit the books!

Why is asking for verification of a statement so unusual and a cause for ridicule?

 

[psvensson]

Why is asking for verification of a statement so unusual and a cause for ridicule?

He just told you what he has observed. To ask him to "verify" the evidence of his senses by citing a peer-reviewed work seems more than a little superfluous.

 

[NER]

As you can see, I did not respond to the point about XTOL. I thought you were referring in a more general way to the preceding discussion.

 

[Kirk Keyes]

NER - I think he was referring to the general tone of the preceding discussion. Don't worry about it.

 

[gainer]

I find this argumentation quite amusing. In my years of experience as a research engineer, I have seen several instances where theory was cited as a reason for some experiment not working, whereas in fact it did work.

One thing you must remember. In years gone past, the image stain left by development was a nuisance to be avoided. You could get that impression from the works of Hurter and Driffield. It happens that the stain left by hydroquinone is mostly avoided by having anything like the usual amount of sulfite in a working solution. Furthermore, in order to get the optimum superadditivity between hydroquinone and either metol or phenidone, a certain amount of suldite is required. That is almost as much as it takes to prevent staining. The ordinary experimenter would not see any staining by hydroquinone, because who compounds an MQ or PQ developer without at least 10 grams of sodium sulfite per liter? I found it for myself because I was interested in sulfite-free developers. Not for environmental reasons, but because sulfite free developers tend to be surface developers that are not hindered as much by the surface charge barrier (I hope I got it right, but really don't care.) You can find such statements in "The Theory of The Photographic Process".

So, I thought I found that hydroquinone in alkaline solution does make a staining developer. Then I found by reading a book that I was right, by gum! I'm glad I found that book. Otherwise I might be hiding in a corner in denial somewhere, fearing I had seen an imaginary ghost image.

 

[srs5694]

Perhaps there's something more explicit in the body text somewhere, or in another issue.

Yes, there is. I don't have the issue in front of me, but he does say something like "Bet you didn't know hydroquinone can be a staining developer." He was right about that!

I thought I remembered such a comment, too, so I went and skimmed the rest of the article, and it's on p. 25: almost exactly the phrase you use, in parentheses, followed by "Hydroquinone is 1,4-dihydroxybenzene. Pyrocatechol is 1,2-dihydroxybenzene. According to theory(1), any developer with two or more active hydroxyl groups will be an active tanning and staining developer." The footnote ("(1)" above) then offers chapter 13 of W. H. Lee's _The Theory of the Photographic Process_ as a citation. I don't happen to have that book to cite it directly, though.

 

[dancqu]

" ... Tanning and staining may not be the same, ... "

One and the same I'd say.

" .... if the developer oxidation product is coloured then there is
likely a link between tanning and the formation of a stain image."

The PRODUCT of the reaction TWIXT the oxidation product and
gelatin is a colored, tanned, gelatin.

"L P Clerc's ... and in a quantity proportional to the amount of
silver halide reduced. ... they polymerize, giving rise to coloured,
tanning substances of the nature of humic acids, ... "

So, there it is from L P Clerc; tanned gelatins of various
colors are the result of a reaction twixt the developer oxidation
products and the gelatin. And below some more from Mr. Clerc.

"Developer - colour - relative intensity - sulphite g/litre

Pyro -- yellow-orange -- 10 -- 11
Catechol -- black -- 10 -- 6
Hydroquinone -- yellow-brown -- 10 -- 2
Chlorhydroquinone -- yellow-brown -- 10 -- 2
Amidol -- reddish-brown -- 8 -- 2
p-Aminophenol -- brownish-black -- 3 -- 2
Metol -- brownish-black -- 2 -- 1
PPD -- Grey -- 1 -- 0
Glycin -- None."

Best, Helen

I can only wonder what is going on with that hydroquinone.
That 2 grams/liter is also a Lith developer sulfite maximum.
Reconcile, if you will, HQ's oxidation products giving lith
development and at the same time those oxidation
products being involved in tanning gelatin. Dan

 

[Tom Hoskinson]

The lith developer may very well be tanning and staining - or it may be that the design of the lith film emulsion prevents/suppresses it. In any case, Bleaching the silver out after development and fixing seems like a good way to tell.

 

[gainer]

I don't recall seeing any formulas for MQ or PQ lith developers. Hydroquinone substituted for catechol in Pyrocat HD will produce a stain image. It is different in color, as the previously posted information says. Sandy King does not find the color as effective for his purposes as catechol.

Hydroquinone, catechol or pyro in TEA can make a single solution staining developer stock solution. The pH won't be high enough to make a lith developer. I think maybe the high silver contrast of lithography keeps whatever stain image there might be from showing.

 

[Gerald Koch]

There is nothing in Xtol to cause a stain image to form. The oxidation products of isoascorbic acid are colorless and more importantly water soluble. If you are seeing a slight magenta stain then this is a small amount of antihalation dye that has not been washed from the film. The oxidation products of Dimezone-S (the other developing agent in Xtol) are also water soluble.

 

[gainer]

I don't recall seeing any formulas for MQ or PQ lith developers. Hydroquinone substituted for catechol in Pyrocat HD will produce a stain image. It is different in color, as the previously posted information says. Sandy King does not find the color as effective for his purposes as catechol.

Hydroquinone, catechol or pyro in TEA can make a single solution staining developer stock solution. The pH won't be high enough to make a lith developer. I think maybe the high silver contrast of lithography keeps whatever stain image there might be from showing.

I should have mentioned that some lith developers depend on the reaction between sulfite and formaldehyde to produce NaOH in the working solution. These are two part developers. The sulfite preserves the hydroquinone in one bath. The formaldehyde is added at time of use. The amount of excess sulfite is probably enough to prevent staining.

 

[Kirk Keyes]

There is nothing in Xtol to cause a stain image to form. The oxidation products of isoascorbic acid are colorless and more importantly water soluble. If you are seeing a slight magenta stain then this is a small amount of antihalation dye that has not been washed from the film. The oxidation products of Dimezone-S (the other developing agent in Xtol) are also water soluble.

Gerald - this may be so, but I've taken an XTOL-processed neg (I think it was FP4+ or Tri-X) and bleached it and there remains a magenta image. Very, very low contrast, and as I said probably too low to make any contribution to the print.

If it is residual antihalation backing - that may be, but after all, it appears identical to a "stain".

 

[Kirk Keyes]

The lith developer may very well be tanning and staining - or it may be that the design of the lith film emulsion prevents/suppresses it. In any case, Bleaching the silver out after development and fixing seems like a good way to tell.

Perhaps the high density of the lith image makes the stain not noticable.

 

[Helen B]

Kirk wrote: "Gerald - this may be so, but I've taken an XTOL-processed neg (I think it was FP4+ or Tri-X) and bleached it and there remains a magenta image. Very, very low contrast, and as I said probably too low to make any contribution to the print.

If it is residual antihalation backing - that may be, but after all, it appears identical to a "stain"."

From the 'Thoughts off the top of my head' department:
Ascorbic acid is a very weak tanning agent, which appears to be helped by the presence of borates. Could it be that the very slight tanning effect makes any dye slightly more difficult to wash out? I realise that there are theoretical reasons to discount this explanation.

Best,
Helen

PS Dan, if you call tanning and staining 'the same' then we apply different meanings to the word same, that's all!

 

[Ole]

I don't think it would be antihalation dye which was left after developing - sensitizing dye is far more likely (unless we're talking 35mm, where the antihalation dye isn't on the back side of the film).

It is conceivable that some of the dye might get preferentially left in the "hardest" part of the emulsion, i.e. where the silver density was highest and tanning strongest.

 

[Kirk Keyes]

Helen, Ole, you guys make good points about the "hardening" of the processed areas with greater optical density possibly making it harder to wash out the dye, whether the dye is antihalation, sensitizing, or other. Not a true tanning or staining process, but one that results in a "stain" nonetheless.

I haven't checked with other non-staining developer/film combinations so I can't say this behavior is unique to the XTOL. Perhaps someone else here has?

 

[sanking]

Helen, Ole, you guys make good points about the "hardening" of the processed areas with greater optical density possibly making it harder to wash out the dye, whether the dye is antihalation, sensitizing, or other. Not a true tanning or staining process, but one that results in a "stain" nonetheless.

I haven't checked with other non-staining developer/film combinations so I can't say this behavior is unique to the XTOL. Perhaps someone else here has?

I have also observed a slight amount of staining with PC-TEA, which is ascorbic acid + phenidone in TEA. It amount to only about log 0.05-0.10 and would not be apparent unless one were to compare densitoimeter readings in Visual and Blue channel.

Sandy

 

[dancqu]

"Hydroquinone, catechol or pyro in TEA can make a single
solution staining developer stock solution.
The pH won't be high enough to make a lith developer."

That is TEA won't make a lith developer of hydroquinone .
Hydroquinone only, of all the usual agents, exhibits
the lith phenomena. BUT TEA MAY!

"I think maybe the high silver contrast of lithography keeps
whatever stain image there might be from showing."

High contrast is not the objective of many who use lith
chemistry. Tan and lith at the same time. How could that
be? The silver halides, gelatin, and chemical products of
reduction are all in intimate contact. Sulfite levels are
at the low needed for tanning and lithing. Dan

 

[gainer]

I have to say what my branch head once said to me. I understand all your words, but I don't understand your sentences. I'm saying this with a big grin on my ugly mug, so don't get upset.

When are those things not in intimate contact? What sulfite levels are we talking about? It takes only about an equal amount of sulfite as hydroquinone to eliminate or at least diminish greatly the staining action of hydroquinone. It takes a whole lot more to get rid of the pyro stain.

We don't always use our potions the way they were intended to be used, but the way they were intended to be used puts some limitations on how we can misuse them. It is difficult to use the lith developers I know of without incurring infectious development. Even Rodinal shows some of those symptoms.
Now I can't remember what I was about to say.

 

[dancqu]

When are those things not in intimate contact?
What sulfite levels are we talking about?

Specifically the chemical products of reduction, in so far as
tanning and lithing, are not present when sulfite levels are high.
That or some other explanation for their being present and
a lack of tanning or lithing.

I think it must be the quinone which causes the tanning. Lith
results are dependent upon it's presence. Is it possible for both
tanning and lithing to proceed simultaneously? The conditions
for both to proceed concurrently are present.

Maximum sulfite levels for tan and lith results are both
the same, 2 grams per liter. Dan

BUT TEA MAY. By that I mean the ph of a TEA solution
containing hydroquinone and a pinch of sulfite may be high
enough to initiate silver halide reduction. Dan

 

[gainer]

I'll check again, but I'm pretty sure you can get a stained silver image with just hydroquinone and TEA in water. No sulfite required. If you want superadditivity with phenidone or metol, a modicum of sulfite is required. I'm also pretty sure that you won't get high enough contrast to call it a lith developer. If you then add some paraformaldehyde, the pH will go way up because of its reaction with sulfite. A lot of fog will result unless you add two or three bunches of bromide. I'm speculating somewhat, but the formula I got for "extreme contrast films" from the 1941 War Department Technical Manualon Basic Photography is:
water at 125 F.....................................................64 ounces
sodium sulfite (des.)..............................................4 ounces
Trioxymethylene (paraformaldehyde).........................1 ounce
Potassium metabisulfite..........................................150 grains
Boric acid crystals.................................................1 ounce
Hydroquinone........................................................3 ounces
Potassium bromide.................................................90 grains
Water to make 1 gallon

I think there is a Kodak lith developer with these ingredients but kept in two parts until use. D-8 maybe?

 

[dancqu]

"I'll check again, but I'm pretty sure you can get a stained silver
image with just hydroquinone and TEA in water. No sulfite required."

Perhaps so. Tests would need be done. If that combination will
tan then it should lith. We're talking Hydroquinone, the ONE
that will tan and lith.

Having given it some thought I'm quite sure that it must be the
semiquinone which does the tanning AND the lithing. Also the
lith phenomenon for the most part follows the tanning.
If sulfite levels are more than very little the formation of quinone
is blocked. In that case, the hydroquinone - quinone reaction
does not take place and there is no exponitial increase
in semiquinone.

"I'm also pretty sure that you won't get high enough contrast to
call it a lith developer. If you then add some paraformaldehyde, the
pH will go way up because of its reaction with sulfite. A lot of fog
will result unless you add two or three bunches of bromide. I'm
speculating somewhat, but the formula I got for "extreme
contrast films" from the 1941 War Department Technical
Manual on Basic Photography is:

water at 125 F.....................................................64 ounces
sodium sulfite (des.)..............................................4 ounces
Trioxymethylene (paraformaldehyde).........................1 ounce
Potassium metabisulfite..........................................150 grains
Boric acid crystals.................................................1 ounce
Hydroquinone........................................................3 ounces
Potassium bromide.................................................90 grains
Water to make 1 gallon

I think there is a Kodak lith developer with these ingredients
but kept in two parts until use. D-8 maybe?"

Once again Mr. Gainer: High contrast is not the objective of many
who use lith chemistry. Full gray scale, pictorial, prints are being
made by at least a few using that chemistry.

The lith developer I compounded by chance, I found later, was of
the Wall's Normal Hydroquinone type; HQ + SO3 + CO3. There are
several formulas for lith developers which have only those three
chemicals plus bromide. Ansco adds a bit of citric acid. Dan