Bichromate Photographs

Abstract

A SINGULAR discovery has recently been made touching the action of light upon substance rendered sensitive by the bichromates of potash and ammonia, which threatens to revolutionise photographic printing altogether, at any rate so far as the production of permanent prints is concerned. The printing by means of silver salts in the ordinary way, which is still in vogue with nearly all portrait photographers, will always find application, by reason of the simplicity of the manipulations and the delicate and pleasing nature of the results, albeit all silver photographs enjoy the unenviable notoriety of being perishable. First of all, they lose their pristine brilliancy and freshness, then a sickly yellowness gives place to the glossy whites of the picture, and finally the deep bronze shadows become of a flat brownish tint, which grows weaker and weaker as time goes on. To secure permanent photographs, which shall possess all the beauty and detail exhibited by silver prints, has been for many years the aim of photographic experimenters, and it was not until Swan and Johnson had contributed their well-known improvements that the production of a delicate photograph in permanent pigments became at all possible. Mechanical photographic processes, where the pictures are printed off in a press, are still beset with many difficulties of a practical nature, the most perfect of them—Woodburytype—requiring further elaboration before perfect prints of large dimensions can be secured.