...continued from technical info on platinum ...
You probably know what a black and white silver gelatin print is ...
Silver prints have been around for a long time. They're beautiful. They're darkroom prints. They're handmade.
But they're common. And silver isn't stable; it oxides and degrades when exposed to air.
Silver prints have surface emulsions that house an image. In effect, the image of a silver print floats on the surface of the paper on which it's printed. As the silver oxidizes, experts say the silver molecules "migrate" to describe the degradation process.
Platinum prints have no surface emulsion. Instead, platinum molecules permanently attach to the paper fibers during the printing process.
Since platinum becomes permanently embedded into the paper, the image - and the image quality - last as long as the paper exists. This could be as long as 3,000 years.
The platinum in a platinum print is not susceptible to migration, oxidation, mirroring, corrosion or any other type of degradation that all silver prints will experience.
Platinum is inert.
It is forever.
How a silver gelatin print is made
Traditional black and white silver prints go through several wet chemical processes.
These processes begin when the printer puts a developed negative into an enlarger and exposes that negative onto a piece of light-sensitive, photographic paper.
The photographic paper consists of layers; 1) a top-layer of light-sensitive gelatin containing silver halide crystals, and 2) a substrate that provides the paper base.
The exposed paper then goes through a developer, toner and a clearing bath.
The top layer that develops the image contains an enormous variety of crystal shapes; it is this almost limitless shape variety that provide the glorious and highly valued continuous tones.
The limitations of silver
While astonishingly beautiful, silver is an unstable metal that oxidizes in air. All silver prints will eventually turn via sulfiding, redox (appears as orange markings on the print), or fading (silver mirroring).
The presence of airborne pollutants and heat and humidity encourage sustained migration of the silver ions. This creates the "silver mirroring" effect, especially in the dark areas of prints.
Toning increases silver's stability by coating it with a less easily oxidized metal (such as gold) or by converting portions of the silver image particles into more stable compounds such as silver selenide or silver sulfide.
Unfortunately, toning treatments have a downside. They affect the look of a silver print and most connoisseurs agree that it is rarely an enhancement.
More technical details about how a platinum print is made...