What is silver plate photography?

Silverplate photography (English) was invented by Daguerre, the chief landscape painter of a famous opera house in Paris, France, in 1839, and the exposed silver salt coating was developed with mercury vapor. The exposure time of this photography method is about 30 minutes, which is much shorter than that of joseph Nicephore Niepce. After the improvement, the exposure time is further shortened and portrait photos can be taken.

The photos taken by this method have the characteristics of thin shadow lines, uniform tone, difficult fading, difficult copying and opposite images. This method of photography is named after the silver plate photography, so it is also called the silver plate photography.

The advantages of silver plate photography are that the photos are realistic, three-dimensional and positive. The disadvantage is that from different angles, the photos will change from positive to negative. In addition, because the image is formed on a very thin layer of silver, it is easy to be damaged, and it may be damaged by rubbing with your fingers. Many existing early silver prints have been damaged. The aqueous solution of sodium is sprinkled on the photo to form a golden protective layer.

Later, the French physicist Fizeau put forward the idea of gilding photos, and published the "gilding method" in 1844, that is, adding gold chloride to sodium thiosulfate aqueous solution, and then scattering it on photos to form a gold protective layer.

A group of photographers came up with a more direct way to put the photos in a glass frame. Also, the use of mercury vapor development may lead to mercury poisoning of photographers. Other disadvantages include difficulty in copying photos and high shooting cost.

However, because the technology has been made public, silver plate photography has been widely circulated all over the world and once became the mainstream photography method. It was not until 1850 s that it was replaced by new methods such as wet-plate collodion photography.

Make plates

Silver-plated photos are formed on a highly polished silver surface. Silver is usually a thin layer on a copper substrate, but other metals (such as brass) can also be used for the substrate, and silver plates can also be made on solid silver sheets.

A very pure silver surface is preferred, but pure silver (92.5% purity) or American coins (90% purity) or even lower grade silver is also useful. In the practice of19th century, the usual raw material Sheffield board was produced by a process sometimes called melt electroplating.

A piece of pure silver was melted on top of a thick copper ingot. When the ingot is repeatedly rolled into a thin plate under pressure, the relative thickness of the two layers of metal remains unchanged. Another method is to electroplate a layer of pure silver on bare copper plate. Sometimes these two technologies are combined to coat Sheffield plate with a layer of pure silver by electroplating.

In order to prevent the corners of the plate from tearing the polished material when polishing the plate, a patented device is adopted to bend the edge of the plate backward, which can also be used as a plate frame to avoid touching the surface of the plate during processing.