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Old 8th April 2011, 11:02 AM
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Default Benzotriazole Strength.

I have just acquired some Benzotriazole with the intention of using it as an anti-fog with some Kentmere Elite paper that is starting to show signs of fogging and that I want to use up. I have never tried anything like this previously. I know I add the solution to the developer in about 10 to 15 ml to 1 litre proportions adding more until the fog is controlled.

Searching the Forum there seems to be some confusion on the strength to mix the working solution. Les McLean in a response in Ask Les talks of a 1% solution but then quotes 1 gm per 1000ml. I thought that was a 0.1% solution. Ansel Adams in the print talks of a 2% solution and on the Silverprint site I found a note suggesting adding 2 gms to hot water but it did not specify a quantity. I have also seen a 10% solution quoted but that seems to be for cooling down the image.

I have been through the Darkroom Cookbook, Ilford Manual of Photography and other similar publications and while they tell you it works there is no definitive answer as to strength for use as an anti-fog.

So, can anybody give me a definitive answer on what % solution for an anti-fog.

Thanks for any help.

Bill
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Old 8th April 2011, 07:51 PM
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In his book The Photographer's Master Printing Course Tim Rudman suggests 5ml per litre of a 1% benzotriazole solution to control fog. As an additive to cool tones down the formulary at the back of the book gives 10g Sodium Carbonate (anhydrous) and 10g Benzotriazole per litre of water. Add 10ml to each litre of developer and increase as necessary. A 1% solution is 1gram per 100ml of water.
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Old 8th April 2011, 09:27 PM
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Default Benzotriazole Strength

Bill,

For fog control start your tests at 1% of developer working slowly up to 5%.

For colour change start your tests at 10%.

Also worth a test with a silver rich paper is 4 minutes development in an active developer (such as Dokumol) followed by a two - four minute immersion in 5% Benzotriazole.

Have fun.
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Old 9th April 2011, 06:55 AM
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Thanks for the answers. Must admit I never looked at Tim's book for an answer. Will mix a batch at 1% and give it a try.

Bill
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Old 10th April 2011, 12:56 PM
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On "Jack's Photographic and Chemistry Site" there is some useful information here and here.
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Old 16th April 2011, 10:11 AM
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Just to point out that using Benzotriazole to cool down tones doesn't seem to work with modern papers, at least according to my tests from 2009.

Tom
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Old 16th April 2011, 08:04 PM
Mike O'Pray Mike O'Pray is offline
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Quote:
Originally Posted by Tom Kershaw View Post
Just to point out that using Benzotriazole to cool down tones doesn't seem to work with modern papers, at least according to my tests from 2009.

Tom
Yes now I come to think of it I had to use high strength benzotriazole for some age-fogged Agfa Premium MCP. It worked OK but didn't seem to have much effect on cooling the tones down.

Either that or my judgement isn't very good at subtle changes.

Mike
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Old 17th April 2011, 06:38 AM
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Quote:
Originally Posted by Tom Kershaw View Post
Just to point out that using Benzotriazole to cool down tones doesn't seem to work with modern papers, at least according to my tests from 2009.

Tom
modern papers are quite neutral, so if you're looking for a bluish tone that isn't very subtle, that's not the way. It can help cooling down warmtone papers.
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Old 17th April 2011, 02:49 PM
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Maxim Muir's Blue Black (which contained a fair amount of Benzotriazole) used to turn Forte Polywarmtone neutral.
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Old 19th April 2011, 10:23 AM
Tom Kershaw Tom Kershaw is offline
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As far as I can work out the only cooltone developer that is unique over what can be acheived with D-72 or equivalent is Harman Cooltone, no longer available as we know.

Tom
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