Here you go: ----- Original Message ----- From: Ann Sanfedele Subject: Re: Help with terminology regarding B&W print wanted
> OUch - I can't even tell if you are kidding or not. tarnish makes > silver black, why would > it be called what makes black silver? but you were kidding, weren't > you? " The shiny metallic deposits are caused by metallic silver on the surface of the paper. How it gets there is a more difficult process to explain. It is usually called mirroring out or silvering out. What happens is that over time imaging silver can begin to oxidize and break down, when this breakdown occurs silver ions break free from the silver imaging particles in the print. These silver ions are both invisible and migratory and can actually move through the gelatin. This movement is halted when these ions run into a reducing agent (such as sulfur) and is reduced back to metallic silver (usually silver sulfide). This occurs most often in the maximum density areas, simply because that is where the most silver is. The reason that it appears on the surface of the print is that that is the most opportune location for these migrating silver ions to come into contact with reducing agents (sulfur in the atmosphere). There is no known cure for this problem. Roger Watson Conservation Department George Eastman House 900 East Avenue Rochester, NY 14607 (716) 271-3361 " - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
