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SOME EARLY APPLICATIONS OF PHOTOGRAPHY 221
Grune employed this method to produce gold ornaments on glass and porcelain. Drawings and patterns of various kinds were photographed ; the image obtained was changed into one of gold, then burnt in, and thus the most beautiful and complicated decorations could be produced without the assistance of the porcelain painter.
If a silver picture be plunged into a solution of platinum instead of a solution of gold, a platinum image is obtained. This assumes a black colour on being burnt into the porcelain. In this manner black portraits, landscapes, etc., have been produced on porcelain.
Pictures of this kind can be prepared in other colours than black. For example, if the photograph is dipped in a combined solution of gold and platinum, the gold and platinum are precipitated on the picture. The image thus obtained, if burnt in, presents a very agreeable violet tint.
Solutions of uranium, of iron, and of manganese effect precipitates on a collodion picture, modifying its colour, and, when burnt in, produce different brownish or blackish tints. There are other means of producing such pyrophotographs. Details will be found in the chapter on the photo-chemistry of the chromium compounds.
The so-called Magic Photography. — Closely connected with Gr line's process for producing pictures on porcelain is what was called magic photography. Some years ago small sheets of white paper were offered for sale which, on being covered with blotting-paper and sprinkled with water, displayed an image as if by magic. The white sheets of paper, to all appearance a blank, were photographs which had been bleached by immersion in a solution of chloride of mercury. If a photograph not containing gold be immersed in a solution of chloride of mercury, a part of the chlorine passes over to the silver of the picture, and changes the brown silver particles into white chloride of silver, which is invisible on the white paper. At the same