[rollei_list] Re: RPA, Efke 25, fixer with hardener?
----- Original Message ----- From: "Mark Rabiner" <mark@xxxxxxxxxxxxxxxx> 
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Monday, March 30, 2009 9:38 PM
Subject: [rollei_list] Re: RPA, Efke 25, fixer with hardener? 


Try without the hardener first.
Its sulfuric acid. Battery acid.
Not great to breath the fumes. Its a little bottle you can just not use. Solution B. just use solution A is Ammonium Thiosulfite. Does not smell 
hardly at all but use rubber gloves anyway.
If you are getting all kinds of scratching then then maybe give it a go. The hardener is even thought of as not archival by some folks as it makes it harder to wash the stuff out of the neg; or in this case the glass plate. 

I'd kill to be able to shoot glass plates.
I believe the look you'd get would be notably sharper than sheet film; 
Even flat sheet film.
Would be interesting to do a side by side comparison and see if it was 
really true.
Its just feel like Atget or somebody.
William Henry Jackson
http://andrewsmithgallery.org/exhibitions/western/jackson.html

Naturally I'd like to be shooting larger ones
At least 5x7's if not 8x10's






Mark William Rabiner
Part B contains the hardener, which is potassium aluminum sulfate, AKA alum or white alum. It also contains a small amount of sulfuric acid. The purpose of the acid is to decrease the pH of the fixing bath to the value that is optimum for the hardener. I am not sure why Kodak uses sulfuric acid rather than acetic acid. It is a non-orgainic acid where acetic is organic but I rather think there might be come reaction that produces some additional sulfite in the fixer. Hardening fixing baths contain a large amount of sulfite, generally about 15 grams/liter. Its purpose is to prevent the decomposition of the thiosulfate by the acid. If no hardener is used the fixing bath does not have to be acid since the pH does not affect the ability of the alum to harden. However, even when no hardener is used fixing baths are often still made acid to prevent carried over developer from becoming active. The sulfite than serves two purposes: one, it prevents decomposition of the thiosulfate, and two, it prevents reaction products from the developer from causing stains. Even when a fixing bath is neutral or alkaline some sulfite is included to prevent oxidation products of carried over developer from causing staining plus it helps to prevent oxidation of the thiosulfate. When the fixing bath is not acid or only slightly acid the amount of sulfite is reduced to about 5 grams/liter The above is true regardless of the form of thiosulfate used, i.e., its the same for a conventional or a rapid fixer. 

--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx 
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