I have a bulk roll of film that has a strong base fog, badly stored probably. I've forgotten the name of the chemical clearing agent to de-fog it. Can anyone help?
Anti-Fog Chemistry
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Benzotriazole:
http://stores.photoformulary.com/benzotriazole/
"Ben - zot -tree- ozzle" is the way I understand you pronounce it. Always gives me pause when I try to pronounce it...
http://stores.photoformulary.com/benzotriazole/
"Ben - zot -tree- ozzle" is the way I understand you pronounce it. Always gives me pause when I try to pronounce it...
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There's no such thing as 'de-fogging' photographic materials. The best you can do is suppress development of low image densities, including fog, but also thin shadows. Hence, film speed will suffer. This is especially the case with potassium bromide, a little less so (apparently) with benzotriazole, although this also incurs a penalty.
Fact is that no chemistry can tell the difference between fog and the image you're trying to record. Hence, if you suppress fog, you also suppress some of the image information.
Personally I wouldn't bother with film to try and suppress fog; if there's fog and also a usable image, simply print through the fog.
Ok, I was thinking of something Pentax Peter Elgar uses on old film. His chemistry knowledge is pretty good. I'll have a go at scanning through the base fog first.
https://www.diyphotography.net/how-i-removed-base-fog-from-old-film-stocks/
Benzotriazole is a restrainer. You can use it with age fogged film with some success, BUT you will lose sensitivity.
See the above article for some methods this person used.
Benzotriazole is a restrainer. You can use it with age fogged film with some success, BUT you will lose sensitivity.
See the above article for some methods this person used.
BLockend, I assume that you have a 400 speed film. If not, a minor adjustment will have to be made with development times. Experiment.
Benzotriazole is only the beginning. Blockend, and others, you have to understand one thing clearly here. With heavily age-fogged film you have film that is sorely lacking contrast because you have only a portion of the Characteristic Curve to get the complete image with. Thus, you engage in a desperate quest for contrast as you suppress half of the Curve so as to avoid a 'dirty negative'.
With even fresh film, I often use Dektol, diluted about 20X, and get great results. Now, this is going to come across as crazy, but with blockend's film, Dektol is a LOW CONTRAST developer. Yes, it is that crazy and true. You need an injection of BOTH hydroquinone AND benzotriazole. In addition, you have to keep the metol VERY low so as not to counter the contrast buildup. (Remember, metol is primarily for threshold density, NOT contrast buildup.). Enough metol to allow the hydroquinone to work but not enough to reduce its contrast buildup.
Over the years I have done countless experiments on this topic and have come to some real, tangible conclusions.
That said, here is a working formula for heavily age-fogged B&W film (NON-chromogenic). My measurements and temps are different from most rational ways, but they are MY ways and they work. Do the conversions yourself, and do not DARE to ask me why I use mL for some powder measurements and grams for others. Do the conversions yourself.
NB: My development temp is 80 Fahr (but you can add more development time if you want to develop at a colder temp). I mix each of the solutions by placing the contents into a PET plastic bottle, somewhat larger than the required size, then place the cap on the bottle, and shake like hell for a few minutes. For decades I have done this and never heed the bullshit about 'oxidation' concerns. That oxidation never manifests, it remains solely in theory. What IS important is to STORE the mixed volume filled to the bottle's rim and capped tightly. If the bottle is designed to hold carbonation, it is adequate for developers. PET plastic is, Period. Film speeds for heavily age-fogged film: I doubt if blockend's film is as fogged as some of the films I have brought back to life, but I have found that in EXTREME cases the speed drops by up to six stops. Blockend, first try four stops more exposure with my formula, then go from there.
>You need a basic developer: full strength Dektol solution, as per Kodak. Store air-tight. This is nothing other than Dektol stock. Call it DS.
>You need hydroquinone to aid in contrast buildup. Make a solution as follows and keep it airtight: 2 mL sodium sulfite,anhydrous + 1 mL of hydroquinone in WTM 25. Mix as much volume as you wish, but for each 25mL wanted, that is your hydroquinone mixture. Call this solution HS.
>You need benzotriazole to suppress the fog. Mix as follows: 1 GRAM benzotriazole in WTM 400mL. Call this restrainer 'RS'. Mix fully, as it is difficult to get all into solution. Warm water helps.
This is how to make 100mL of working solution of fog-suppressant developer. (If you want to make more volume, do your conversions): 1 part DS + 10 parts HS + 10 parts RS + 79 parts water. I use 80 Fahr for 8 minutes, continuous agitation. If your agitation differs you might have to make a minor time adjustment.
PROBLEMS? If you get excess density, you have either over exposed (blockend, try four stops more exposure, initially). If you get almost no density but very clear film: you need either a bit of carbonate or a tiny bit more DS, perhaps, or maybe less RS so your development is not so suppressed. If the density is somewhat low, use common sense by developing for a longer time. Experiment with clip tests. If you use whole rolls for experiments, you are plain nuts and wasteful. When doing this paper 'clip test' be certain to place a penny on the paper so you will be in a position to judge the base fog. Remember, the longer you can develop the paper without that coin area attaining more than medium gray, the higher will be your contrast. And ... you might be developing the paper as long as four or five minutes.
NB: This works also for age-fogged paper. Usually, however I would give twice the DS then the same amounts of the HS and RS as for with film. Remember to give up to six (!) stops more exposure for 'impossible' paper where with normal development an image would hardly appear at all. Then, after this, Farmers' puts the icing in the cake with its beautiful contrast enhancement. Experiment a lot and cut tiny pieces of paper for your 'clip tests'. If you use whole sheets of paper, you are more nuts than David Lyga.
- David Lyga
.
Benzotriazole is only the beginning. Blockend, and others, you have to understand one thing clearly here. With heavily age-fogged film you have film that is sorely lacking contrast because you have only a portion of the Characteristic Curve to get the complete image with. Thus, you engage in a desperate quest for contrast as you suppress half of the Curve so as to avoid a 'dirty negative'.
With even fresh film, I often use Dektol, diluted about 20X, and get great results. Now, this is going to come across as crazy, but with blockend's film, Dektol is a LOW CONTRAST developer. Yes, it is that crazy and true. You need an injection of BOTH hydroquinone AND benzotriazole. In addition, you have to keep the metol VERY low so as not to counter the contrast buildup. (Remember, metol is primarily for threshold density, NOT contrast buildup.). Enough metol to allow the hydroquinone to work but not enough to reduce its contrast buildup.
Over the years I have done countless experiments on this topic and have come to some real, tangible conclusions.
That said, here is a working formula for heavily age-fogged B&W film (NON-chromogenic). My measurements and temps are different from most rational ways, but they are MY ways and they work. Do the conversions yourself, and do not DARE to ask me why I use mL for some powder measurements and grams for others. Do the conversions yourself.
NB: My development temp is 80 Fahr (but you can add more development time if you want to develop at a colder temp). I mix each of the solutions by placing the contents into a PET plastic bottle, somewhat larger than the required size, then place the cap on the bottle, and shake like hell for a few minutes. For decades I have done this and never heed the bullshit about 'oxidation' concerns. That oxidation never manifests, it remains solely in theory. What IS important is to STORE the mixed volume filled to the bottle's rim and capped tightly. If the bottle is designed to hold carbonation, it is adequate for developers. PET plastic is, Period. Film speeds for heavily age-fogged film: I doubt if blockend's film is as fogged as some of the films I have brought back to life, but I have found that in EXTREME cases the speed drops by up to six stops. Blockend, first try four stops more exposure with my formula, then go from there.
>You need a basic developer: full strength Dektol solution, as per Kodak. Store air-tight. This is nothing other than Dektol stock. Call it DS.
>You need hydroquinone to aid in contrast buildup. Make a solution as follows and keep it airtight: 2 mL sodium sulfite,anhydrous + 1 mL of hydroquinone in WTM 25. Mix as much volume as you wish, but for each 25mL wanted, that is your hydroquinone mixture. Call this solution HS.
>You need benzotriazole to suppress the fog. Mix as follows: 1 GRAM benzotriazole in WTM 400mL. Call this restrainer 'RS'. Mix fully, as it is difficult to get all into solution. Warm water helps.
This is how to make 100mL of working solution of fog-suppressant developer. (If you want to make more volume, do your conversions): 1 part DS + 10 parts HS + 10 parts RS + 79 parts water. I use 80 Fahr for 8 minutes, continuous agitation. If your agitation differs you might have to make a minor time adjustment.
PROBLEMS? If you get excess density, you have either over exposed (blockend, try four stops more exposure, initially). If you get almost no density but very clear film: you need either a bit of carbonate or a tiny bit more DS, perhaps, or maybe less RS so your development is not so suppressed. If the density is somewhat low, use common sense by developing for a longer time. Experiment with clip tests. If you use whole rolls for experiments, you are plain nuts and wasteful. When doing this paper 'clip test' be certain to place a penny on the paper so you will be in a position to judge the base fog. Remember, the longer you can develop the paper without that coin area attaining more than medium gray, the higher will be your contrast. And ... you might be developing the paper as long as four or five minutes.
NB: This works also for age-fogged paper. Usually, however I would give twice the DS then the same amounts of the HS and RS as for with film. Remember to give up to six (!) stops more exposure for 'impossible' paper where with normal development an image would hardly appear at all. Then, after this, Farmers' puts the icing in the cake with its beautiful contrast enhancement. Experiment a lot and cut tiny pieces of paper for your 'clip tests'. If you use whole sheets of paper, you are more nuts than David Lyga.
- David Lyga
.
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This is incorrect.
It is pronounced "Benz-o-try-a-zohl". The "tri" in the name denotes three nitrogens in part of its structure, and is pronounced the same as in triathlon.
Ben zo TRI ah zole
Well good. Glad to have an EASIER pronunciation!
Wow, what a comprehensive reply. I've learnt a lot. My initial question was based on the misapprehension that fogged film could be retrospectively cleared, in the manner of Farmer's Reducer (for dense negatives) or chromium intensifier (for thin ones). You speak like a man familiar with the subject of restricted tonality and/or base fog, which interests me almost as much as the reply. Development modification had never occurred to me, until now. Thank you for the responses.
After years of experimentation trying to spend as little as possible on paper, film and chemicals, I think that I deserve that applause and accolade. Not smarter, just more persistent.
Yes, retrospectively, the fog can be suppressed, but ...... What I do is to try to obviate as much fog as possible in the development stage. Then, to clear out with finality, I might dunk in VERY, VERY dilute Farmers' to fully clear that base. I want that finality to take maybe five to ten minutes so that I can handily avoid disaster with too much reduction. But, if you follow my initial ways, you might be able to avoid the necessity for post fix reduction.
The major problem with relying solely upon Farmers' for the total clearance is that Farmers', actually reduces negative contrast, not enhances it like with paper. Best to do the major portion of negative work in the development stage. - David Lyga
Yes, retrospectively, the fog can be suppressed, but ...... What I do is to try to obviate as much fog as possible in the development stage. Then, to clear out with finality, I might dunk in VERY, VERY dilute Farmers' to fully clear that base. I want that finality to take maybe five to ten minutes so that I can handily avoid disaster with too much reduction. But, if you follow my initial ways, you might be able to avoid the necessity for post fix reduction.
The major problem with relying solely upon Farmers' for the total clearance is that Farmers', actually reduces negative contrast, not enhances it like with paper. Best to do the major portion of negative work in the development stage. - David Lyga
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I have only heard of using benzotriazole on photo paper fog, never film, until here. With paper, it is used, more or less, to try to salvage it. The prints that I have seen never looked as good as fresh, unfogged paper yielded. I dump mine and try to learn from the experience. With film, as said above, print through the fog. If there is too much fog for that, don't waste your time on it if you are like me and am unable to spend as much time in the darkroom as you would like. David's idea on post development treatment of film is probably the best answer for film fog......Regards!
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Yes, and worth a sticky for your endeavours.
No such sticky will ever manifest. I am not a 'chosen' on photrio. (It is not WHAT you write, but WHO you are that counts. - David Lyga
The thread where David has given his method for developing C41 film in B&W chemistry also deserves to be sticky. Simple effective method that gives much superior b&w negatives than the naive method.
Again, Raghu, both David Goldfarb and Sean determine 'sticky status' based wholly upon WHO YOU ARE AND NOT CONTENT. I have contributed mightily over the years but
because I am too outspoken,
my chance for a sticky is broken
no chance of a moderator being awoken
(indeed, we will have to wait until I am croakin')
It is not only them here on photrio, but in life, in general. You 'make it' in life if you are 'trendy'. (Watch this post get deleted so as to uphold the photrio image!!!)
- David Lyga
This post should be deleted because it contributes nothing to this thread
And I am the ONLY one who ever temporarily went 'off topic'? The percentages are in my favor, frog eater. - David Lyga,
There is a photog named Daniel Keating who has been experimenting with developing film for extended times in very cold developer(as cold as 52F), with and without the benzotriazole and has had promising results suppressing base fog on very old film. I would hazard a guess the low temps help the developing agent be even more selective in what it develops, but who knows? Its another avenue to explore.
Thats a good question. No idea what is going on except maybe the fogged film was derated enough to allow the shadow detail to show and the developer simply left the less exposed relatively untouched. I havent seen much from Keating about this in the last month or so. Hes on a facebook group called The Darkroom.
I tend to doubt whether that 'cold' temp is even relevant to the fog question. Certainly, more development would be necessary, but it is a good topic to someday explore. However, my doubts stem from the fact that hydroquinone, the contrast component in developers, stops working when below 55F. - David Lyga
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One thing to always keep in mind is that film and developer make no distinction between threshold density and base fog. It is all one and the same to the chemistry and emulsion.
With fog suppressing developers you are subordinating, indeed, attempting to extinguish base fog (which includes threshold density). This is why it becomes essential to give a lot more exposure to the film, in order to place the image onto the Characteristic Curve at a level sufficiently high enough to avoid the 'elimination area' on the lower portion of that Curve. In essence, you are dealing with a truncated Curve and have to make the best of its inherent limitations. - David Lyga
What I do in those situations is to develop with short times and strong dilution, HC 110 dilution B.
I discussed only peripherally the use of age-fog suppressing developers for paper. Here is a formal formula which might help some. It is similar to the one for film, but uses twice the amount of DS. In addition, mix a NEW solution for carbonate as follows. Buy some sodium carbonate, mono. You can simply buy either Arm and Hammer washing soda or, as I do, buy the store brand (I buy ShopRite's). Although many will say that this is the anhydrous version (even the Darkroom Cookbook says so, erroneously) it is, in fact, the more stable 'mono' version. (I called Church & Dwight to confirm). Here is the carbonate formula, again in mL. Call this CS. 2mL sodium carbonate, mono in WTM 25mL. (Thus if you want to mix, say, 100mL, you use 8mL of sodium carbonate.) (You do not HAVE to use any carbonate, but it will cut down you needed development time from maybe four or five minutes to maybe two or three minutes; this makes things easier to manage.) Now the paper developer for heavily age-fogged paper:
To make one LITER of working solution (strongest formula):
50 DS
100 HS
100 RS
50 CS
in WTM 1000
Remember these things: again you must overexpose the paper: up to six stops more exposure, so as to place the image onto the midpoint of the Characteristic Curve.
With paper that is not extremely bad, use this formula and give, maybe, only about two to four stops more exposure:
100 DS
50 HS
50 RS
50 CS
in WTM 1000
General rules for developing age-fogged paper:
Your supreme quest is to obtain contrast without obtaining base fog. Sufficient contrast is gotten ONLY with ample development. However, the 'catch-22' is that 'ample development' brings about base fog!!! Thus, here is what you do for the compromise: ALWAYS USE A COIN ON THE PAPER BEING EXPOSURES THAT ARE MEANT TO DETERMINE THE EXPOSURE AND DEVELOPMENT TIMES. That said, remember, the goal here is BOTH to get contrast AND to get a white base.
Cut many many tiny pieces of paper (1" X 2"?). Make an exposure about 4X normal with the coin in place. Develop in the weaker of the two formulas. Note how dense the coin area is in comparison with the image. If the coin area is darker than mid-way between white and black, you gave too much development. Either use my stronger formula (if you had used my second formula) or cut down the development time. You cannot have an unexposed coin area that is darker than that midpoint. Experiment and write down what you are doing in each case. I have turned rotten, disgusting paper into palatable images.
Sometimes, paper is so bad it seems only kind of OK with this procedure, but still needs Farmers' Reducer after the fix. Because this is a process which we never wish to take to finality (don't want blank paper) we use it simply to clear up the drabness within the print. My "Farmers" formula differs a bit from Kodak's.
First mix a potassium ferricyanide solution. Call is FS. 3mL potassium ferricyanide in WTM 200mL.
Next, use FRESH (unused) fixer in 'PAPER strength' dilution. Call this FIX.
MY "Farmers'" formula is simply 1 part FS + 1 part FIX. However, we wish to usually add much water, up to 20X so as to slow down the procedure and make its reduction manageable. The reduction emphasizes the lowest tones; thus, contrast will be delightfully enhanced. Remember the combined mixture lasts only about 15 minutes when used at full strength, much longer when highly diluted with water.
FINALLY, remember that this information will never be awarded status as a sticky. So be certain to either bookmark it or go crazy trying to find it in years hence. Not all of us qualify for such lofty status, especially not David Lyga. - David Lyga
To make one LITER of working solution (strongest formula):
50 DS
100 HS
100 RS
50 CS
in WTM 1000
Remember these things: again you must overexpose the paper: up to six stops more exposure, so as to place the image onto the midpoint of the Characteristic Curve.
With paper that is not extremely bad, use this formula and give, maybe, only about two to four stops more exposure:
100 DS
50 HS
50 RS
50 CS
in WTM 1000
General rules for developing age-fogged paper:
Your supreme quest is to obtain contrast without obtaining base fog. Sufficient contrast is gotten ONLY with ample development. However, the 'catch-22' is that 'ample development' brings about base fog!!! Thus, here is what you do for the compromise: ALWAYS USE A COIN ON THE PAPER BEING EXPOSURES THAT ARE MEANT TO DETERMINE THE EXPOSURE AND DEVELOPMENT TIMES. That said, remember, the goal here is BOTH to get contrast AND to get a white base.
Cut many many tiny pieces of paper (1" X 2"?). Make an exposure about 4X normal with the coin in place. Develop in the weaker of the two formulas. Note how dense the coin area is in comparison with the image. If the coin area is darker than mid-way between white and black, you gave too much development. Either use my stronger formula (if you had used my second formula) or cut down the development time. You cannot have an unexposed coin area that is darker than that midpoint. Experiment and write down what you are doing in each case. I have turned rotten, disgusting paper into palatable images.
Sometimes, paper is so bad it seems only kind of OK with this procedure, but still needs Farmers' Reducer after the fix. Because this is a process which we never wish to take to finality (don't want blank paper) we use it simply to clear up the drabness within the print. My "Farmers" formula differs a bit from Kodak's.
First mix a potassium ferricyanide solution. Call is FS. 3mL potassium ferricyanide in WTM 200mL.
Next, use FRESH (unused) fixer in 'PAPER strength' dilution. Call this FIX.
MY "Farmers'" formula is simply 1 part FS + 1 part FIX. However, we wish to usually add much water, up to 20X so as to slow down the procedure and make its reduction manageable. The reduction emphasizes the lowest tones; thus, contrast will be delightfully enhanced. Remember the combined mixture lasts only about 15 minutes when used at full strength, much longer when highly diluted with water.
FINALLY, remember that this information will never be awarded status as a sticky. So be certain to either bookmark it or go crazy trying to find it in years hence. Not all of us qualify for such lofty status, especially not David Lyga. - David Lyga
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