Collodion

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Chemical

Collodion is a solution of nitrocellulose in ether or acetone, sometimes with the addition of alcohols. Its generic name is pyroxylin solution. It is toxic and highly flammable. As the solvent evaporates, it dries to a celluloid-like film. It was discovered about 1846 by the French chemist and writer Louis Ménard.

• Celloidin is a pure type of pyroxylin used to embed specimens which will be examined under a microscope. [1]

Photography (also known as the Wet Plate Collodion process)

In 1851, the Englishman Frederick Scott Archer discovered that collodion could be used as an alternative to albumen on glass plates. This also reduced the exposure time when making the image. This became known as the wet plate Collodion or wet collodion method. Collodion was also grainless and colorless, and allowed for one of the first high quality duplication processes, also known as negatives. This process also produced positives, the Ambrotype and the Ferrotype (aka Tintypes).

The process was very involved and included the following steps:

• Clean the glass plate (extremely well)
• Flow the glass plate with "salted" (iodide/bromide) Collodion
• Immerse the plate in a silver nitrate bath (for 3-5 minutes)
• Expose the plate (can range from less than a second to several minutes)
• Develop the plate (using an iron based developer)
• Fix the plate (with potassium cyanide or sodium thiosulfate)
• Varnish the plate (with a varnish made from gum sandarac, alcohol and lavender oil)

All of this was done in a matter of minutes, which meant that the photographer had to carry the chemicals with him wherever he went.

Richard Norris, a doctor of medicine and professor of physiology at Queen's College, Birmingham, is generally credited with the first development of dry collodion plate in the 1860's. In 1894 he took out a new patent for dry plate used in photography.

Medical

• Compound W Wart Remover consists of acetic acid and salicylic acid in an acetone collodion base.
• Pyroxlin solution is also used presently in MedTech's NewSkin liquid bandage product.

Other Uses

• Collodion is widely used to glue electrodes to the head for electroencephalography.

• Pyroxylin with added pigments is used as a nitrocellulose lacquer.

• It was also added to nitroglycerine to stabilise it as blasting gelatine.
• Collodion is also used in theatrical makeup for various effects, such as simulating old-age wrinkles or scars.
• Similarly, it was sometimes used in boxing and other applications to cover up cuts. However, it has been generally replaced by the less toxic Liquid Bandage, which includes pyroxylin as an ingredient.
• Collodion also finds use in the cleaning of optics such as telescope mirrors. The collodion is applied to the surface of the optic, usually in two or more layers. Sometimes a piece of thin cloth is applied between the layers, to hold the collodion together for easy removal. After the collodion dries and forms a solid sheet covering the optic, it is carefully peeled away taking contamination with it.