PORCELAIN PAPER. —A paper having a prepared surface resembling finely-ground por celain, and upon which very effective silver prints may be made, as the preparation, although without gloss, serves to keep the image on the surface.
The following instructions for its manufacture have been published.* Any sheet of a Saxe, Rives, or other photographic paper is coated with a warm solution of gelatine, holdifig in suspension sulphate of barytes, or finely-powdered kaolin. After raising the paper from this emulsion it is suspended in the air until dry, when it is immersed in a solution of alum, tannin or any other substance by which gelatine is rendered insoluble. The body of the paper is thus imbued with the gelatine, and its surface has a fine texture, the pores being all filled up.
When the paper is to be used it is salted by floating it upon a bath of chloride of ammonium and water, about four grains to the ounce of water. In this state it will keep well for many months. It is sensitized by being floated upon a bath of ammonio-nitrate of silver. An ounce
of the nitrate is dissolved in sixteen ounces of water, and strong ammonia, added drop by drop, with constant stirring, until the dark precipitate at first thrown down is just redissolved. Although the way here described is that by which singurlaly fine specimens have been prepared, yet results indistinguishable from these may be produced by sensitizing on a plain nitrate of silver solution, provided that after the paper is dry it is well fumed over ammonia, by which a great degree of richness is imparted to the tone.
After removal from the printing frame the proofs are washed first in plain water and after ward in water containing a little chloride of sodium, say a grain to the ounce. Then follow ton ing and fixing, the prints acquiring a fine purple in the gold bath. On removal from the hypo sulphite of soda it is recommended to wash the prints in three changes of warm water, followed by a prolonged immersion in cold water.