Re: Archival washing at home
----- Original Message ----- From: "John E. Simmons" <email@example.com>
Sent: Monday, September 24, 2007 8:37 AM
Subject: Re: Archival washing at home
I don't know for sure, and I don't really have a way to test. However, Ilford for their traditional materials, recommends multiple changes of water in a tray. It would seem that alt process would be the same - although perhaps a few more changes than for silver gelatin. The pump helps keep the prints separated, and in a large tray with several liters of water, it seems to wash just fine. A test with a hypo test kit shows no residual hypo - again with silver gelatin.Ilford's recommendation is really to conserve water although successive baths _with constant agitation_ may result in better washing than in some running water washers. For single prints a Kodak tray syphon works fine. The tray should be larger than the print to allow circulation of the water. Care must be used to prevent prints from clinging to the bottom.
I am not at all sure if the process of washing for alternative materials is the same as for silver-gelatin. For conventional S-G coated on untreated paper (not RC) the washing out is partially a diffusion process, mostly for the emulsion, and partially frictional for hypo bound to the paper fibers. It is the latter that results in the very long wash times for "fiber" based paper. For silver-gelatin the wash rate is also dependant on the pH of the emulsion relative to its isoelectric point and the pH range over which white alum hardener acts as a mordant. This may not apply to the paper fibers.
It was discovered nearly fifty years ago that Sodium Sulfite acts as an ion exchange medium for hypo. It is very effective for gelatin emulsion but much less so for the hypo stuck to the paper fibers. It _may_ be of use in alternative printing process but I don't know what effect the sulfite might have on some of them. Certainly it would not be suitable for materials like Cyanotype which are bleached by alkaline solutions.
Los Angeles, CA, USA