The platinum/palladium printing process has been in existence nearly as long as photography itself. Commercially produced platinum printing papers first became available in the 1880's and by the turn of the century platinum prints were very popular, valued for their beauty and their intrinsic permanence.
Platinum and palladium are two of the most inert elements in existence which contributes greatly to the extreme archival stability of platinum prints. There is a documented case where platinum prints aboard a sunken ship were brought to the surface 20 years later in excellent condition.
With the onset of World War I, platinum family metals were hard to come by in the US and platinum papers had to be imported from Europe. By 1941, commercially produced platinum papers were no longer available. Print makers who desire the unique and beautiful qualities of platinum create their own printing paper by mixing the light-sensitive chemicals and coating paper by hand. Many print makers thrive by working this way, gaining both technical control and personal satisfaction from this hand-made approach to photographic print making.
The process involves mixing very small quantities of a sensitizer solution (ferric oxalate) with solutions containing the platinum and/or palladium metals. This mixture is then applied to fine rag paper or other media, using either a brush or a glass rod which evenly spreads the solution across the paper. The platinum mixture is only sensitive to ultraviolet light and is therefore a contact printing process (the negative must be the same size as the desired print). The ferric oxalate in the solution reacts with UV light to reduce the platinum metal out of the solution, thus making the image on the paper. The platinum particles are embedded within the fibers of the paper which results in an image that is as permanent as the paper itself. This venerable process has become more and more popular in recent years. Platinum prints are valued by galleries, museums and art collectors for their archival stability as well as their unmatched beauty.