Monday, April 25, 2005
Note about using Benxotriazole to get rid of fogging on old paper.
" noWrap width="1%" bgColor=#cc8600>Richard Knoppow
Apr 25, 12:16 am show options
Newsgroups: rec.photo.darkroom
From: "Richard Knoppow" - Find messages by this author
Date: 25 Apr 2005 00:16:33 -0700
Local: Mon,Apr 25 2005 12:16 am
Subject: Re: Paper: How old is too old?
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Some papers age better than others but storage conditions are also important. Heat is the enemy and tends to accelerate fogging. One way to use fogged paper is to add Benzotriazole to the developer. Benzotriazole is available from suppliers of photographic chemicals and is widely ued in Phenidone developers where bromide is not very effective. Bromide will also suppress fog but Benzotriazole is more effective. I don't have my reference available at the moment (I am away from home) but Grant Haist has a chart of amounts of Benzotriazole to use for both paper and film. I will try to find it later. I have recently used some Ilford Multigrade IV Deluxe which is about ten years old. It shows no fog or reduction in contrast. I've found that old Agfa paper generally holds up well. Kodak paper does not seem to do so well. One reason paper ages faster now is that Cadmium compounds can no longer be added due to environmental concerns. Cadmium serves several purposes in emulsions but preserving the emulsion is one of them. Fog in old emulsions is most often due to the continuation of a process known as ripening. Ripening is a normal part of the emulsion making process during which the silver halide grains gain in sensitivity. However, it is supposed to stop once the emulsion is finished. Various substances are added to the emulsion during the finishing step to prevent ripening from continuing after the emulsion is coated. Sometimes it doesn't work. One reason cold storage preserves film and paper is that it very substantially slows down after coating ripening. All variable contrast filters are available in sets of 6x6 inch gelatin or plastic sheets. These are used above the negative. They can be cut down for smaller enlargers. Kodak, Ilford, and Agfa all make filter sets. Each is tailored for the particular paper although any set can be used with any paper with some adjustment in exposure and variation in contrast.
-- Richard Knoppow dickb...@ix.netcom.com
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" noWrap width="1%" bgColor=#802f97>Nicholas O. Lindan
Apr 25, 8:51 am show options
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From: "Nicholas O. Lindan" - Find messages by this author
Date: Mon, 25 Apr 2005 15:51:08 GMT
Local: Mon,Apr 25 2005 8:51 am
Subject: Re: Paper: How old is too old?
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"Richard Knoppow" wrote
> One way to use fogged paper is to add Benzotriazole I have found the best/cheapest way to handle BT is to buy 100g from B&H or Photographers' Formulary and dump it into 1 pint (~500ml) of 91% [or thereabouts] drugstore isopropyl alcohol. Total cost is $18, including the nifty storage bottle.
This makes a 2% solution. I start at ~1.5ml/liter, but use Richard's numbers or experiment to find what works best for your paper and developer.
Edwal's "Liquid Orthazite" costs about 30 times more than the do-it-yourself solution ($12.95/4oz of 0.2%).
> I've found that old Agfa paper generally holds up well. I will second this. But new Agfa paper doesn't, it is one of the worst, IMNSHO.
" noWrap width="1%" bgColor=#cc8600>Richard Knoppow
Apr 25, 12:16 am show options
Newsgroups: rec.photo.darkroom
From: "Richard Knoppow"
Date: 25 Apr 2005 00:16:33 -0700
Local: Mon,Apr 25 2005 12:16 am
Subject: Re: Paper: How old is too old?
Reply Reply to Author Forward Print Individual Message Show original Report Abuse
Some papers age better than others but storage conditions are also important. Heat is the enemy and tends to accelerate fogging. One way to use fogged paper is to add Benzotriazole to the developer. Benzotriazole is available from suppliers of photographic chemicals and is widely ued in Phenidone developers where bromide is not very effective. Bromide will also suppress fog but Benzotriazole is more effective. I don't have my reference available at the moment (I am away from home) but Grant Haist has a chart of amounts of Benzotriazole to use for both paper and film. I will try to find it later. I have recently used some Ilford Multigrade IV Deluxe which is about ten years old. It shows no fog or reduction in contrast. I've found that old Agfa paper generally holds up well. Kodak paper does not seem to do so well. One reason paper ages faster now is that Cadmium compounds can no longer be added due to environmental concerns. Cadmium serves several purposes in emulsions but preserving the emulsion is one of them. Fog in old emulsions is most often due to the continuation of a process known as ripening. Ripening is a normal part of the emulsion making process during which the silver halide grains gain in sensitivity. However, it is supposed to stop once the emulsion is finished. Various substances are added to the emulsion during the finishing step to prevent ripening from continuing after the emulsion is coated. Sometimes it doesn't work. One reason cold storage preserves film and paper is that it very substantially slows down after coating ripening. All variable contrast filters are available in sets of 6x6 inch gelatin or plastic sheets. These are used above the negative. They can be cut down for smaller enlargers. Kodak, Ilford, and Agfa all make filter sets. Each is tailored for the particular paper although any set can be used with any paper with some adjustment in exposure and variation in contrast.
-- Richard Knoppow dickb...@ix.netcom.com
");
//-->
Reply
" noWrap width="1%" bgColor=#802f97>Nicholas O. Lindan
Apr 25, 8:51 am show options
Newsgroups: rec.photo.darkroom
From: "Nicholas O. Lindan"
Date: Mon, 25 Apr 2005 15:51:08 GMT
Local: Mon,Apr 25 2005 8:51 am
Subject: Re: Paper: How old is too old?
Reply Reply to Author Forward Print Individual Message Show original Report Abuse
"Richard Knoppow"
> One way to use fogged paper is to add Benzotriazole I have found the best/cheapest way to handle BT is to buy 100g from B&H or Photographers' Formulary and dump it into 1 pint (~500ml) of 91% [or thereabouts] drugstore isopropyl alcohol. Total cost is $18, including the nifty storage bottle.
This makes a 2% solution. I start at ~1.5ml/liter, but use Richard's numbers or experiment to find what works best for your paper and developer.
Edwal's "Liquid Orthazite" costs about 30 times more than the do-it-yourself solution ($12.95/4oz of 0.2%).
> I've found that old Agfa paper generally holds up well. I will second this. But new Agfa paper doesn't, it is one of the worst, IMNSHO.
