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> Perceptol Formula |
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#21
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I was not annoyed, but I was puzzled as to why Technidol was mentioned.
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#22
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Quote:
__________________
An old dog learning new tricks |
#23
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THis formula is D23 with added Sodium Chloride & has been known for many years.
Quote:
Ilford published a paper about this in 1965, ID-11 can be turned into a Extra Fine Grain developer by adding 40 g/litre Ammonium Chloride and doubling the dev time and increasing exposure by 50% Microdol-X has metabisulphite and boric acid as preservative to help stability in the powder form, although metabisulphite is used in D25 to turn a fine grain dev into an extra fine grain dev by reducing the alkalinity. Ilford also use a very small amount of Metabisulphite in some of their powdered devs (for example Bromophen) along with the developing agents. Mac |
#24
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#25
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Not being a chemist, what does the Sodium Chloride actually do other than reduce the effective film speed? The Perceptol 'look' is very different to thet with D23 - so how does is work?
Rob |
#26
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Quote:
It might be easier to ask either Bill Troop or Ron Mowrey (Photo Engineer) for an in depth explanation if you don`t mind being blinded with science. In the thread (on the other side) Bill mentions that Richard Henn who formulated D-23, D-25 and DK-25R replenisher, wanted to avoid using bisulphite in the Microdol formula because of the very long development times required. Henn also found that the amount of Elon in D-23 was excessive for the newer thin emulsion films that were then becoming available, hence 5 grams per litre of stock. I`m not sure of how the chloride works to make the grain finer. Provided the weight of sulphite and chloride in the replenisher is the same as in the developer, then an approximate formula for that would be: REPLENISHER. Metol = 6.3 grams Sodium sulphite, anhydrous = 100 grams Sodium chloride = 30 grams Sodium carbonate, monohydrate = 8 grams WTM 1 litre of stock. In the commercial Kodak developers, there is a very complex method for packaging developers which are compounded into a single-powders, that involves the use of boric anhydride to protect them reacting with the other components until they`re mixed with water, but that`s another story which is better explained by Ron and others in the know. Microdol-X is said to be Microdol with the addition of an anti-stain agent which helps to prevent dichroic fog. |
#27
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Thanks Pete
Thanks Pete, that recipe will save me hunting all over Singapore for Perceptol next week
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#28
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My understanding is that sodium triphospahte sequesters calcium and magnesium ions- in other words it acts as a water softener. It also acts as a pH buffer. This answer is perhaps not a lot of practical use, but it does close out Barry's question above. Niall |
#29
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Indeed, thanks Niall.
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Cheers, Barry |
#30
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I have just come across this thread whilst having a look around and sat next to my ex chemist wife. What is Metol? Where would one buy these chemicals?
How much cheaper does it work out mixing your own?
__________________
Sorry for all the questions but I am totally new to all this and it isn't as easy as it looks Been heavily into digital for several years and just starting with the art of film and developing the film and prints myself. I am here to learn and to share with others. |
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