Thanks, Wheatfield! Just as much as I wanted to know - The "silvering" term was what was essential for me to put in the description, I think. I'm crossing my fingers this is a valuable postcard. I kinda hate to part with it - so lovely!
annsan William Robb wrote: > 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 . - 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 .
