From: Gordon J. Holtslander (holtsg@duke.usask.ca)
Date: 07/28/03-10:26:29 PM Z
Try finding some references on cleaning plate for collodion wet plates. I
think these had to be very clean to work.
Collodion had the same problem you are dealing with - getting an emulsion
to stick to a glass plate.
some coated with a layer of albumin, and collodion on top of that.
>From http://photography.about.com/library/weekly/aa112502b.htm
--- The glass needs to be clean and absolutely dust free. Glass was cleaned by immersion for an hour or more in a strong nitric acid solution or by an alkaline solution such as potassium carbonate or other glass cleaning solution. It was then be fully rinsed and dried in a rack. The edges of the glass were rubbed with a file or a carborundum stick, which removed any sharp edges that could cut the hands of the photographer. It was also found that this improved the adhesion of the collodion to the glass, which otherwise tended to peel from the edges. An alternative method to prevent this was to wipe the edges of the glass with some rubber solution - this was done just before coating. Polishing the glass The glass plate was then polished, usually using either 'rottenstone' or 'powdered tripoli' with alcohol. The plates were held in a special clamp to make this easier and avoid any finger marks. Rottenstone is like pumice, but finer. Tripoli is a mineral found in Seneca, Mo., and used in most metal polishes. When the alcohol had all evaporated, the remaining dust was removed with a soft cloth and the polishing completed with a clean chamois leather. It was vital that the surface be dust-free before coating. The edges could be coated with rubber solution at this point by dragging a piece of cotton wool with a few drops of the solution on it around all four edges. Sometimes the plate was coated with a thin albumen layer before the collodion coating. Albumen (made from egg white) adheres better to glass and similar materials, as anyone with experience of washing up dishes will know. ---- Gord On Mon, 28 Jul 2003, Darryl Baird wrote: snip > If the gum/dichromate/cyano combo is a bust. I'll go back to gelatin. We > began there, but I wasn't involved yet and I think the glass wasn't > clean enough: the cyano layer moved all around, forming a lumpy mess. I > moved to using sodium hydroxide (5% solution) to clean the glass, > followed by distilled water and a clean paper towel wiping. Very clean! > --------------------------------------------------------- Gordon J. Holtslander Dept. of Biology holtsg@duke.usask.ca 112 Science Place http://duke.usask.ca/~holtsg University of Saskatchewan Tel (306) 966-4433 Saskatoon, Saskatchewan Fax (306) 966-4461 Canada S7N 5E2 ---------------------------------------------------------
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