The Wet Collodion Process

Thomas Rodger

Below are some extracts from Thomas Rodger's paper On Collodion Calotype,
 read to the Royal Scottish Society of Arts in Edinburgh in February 1854.

4

Coat the Plate

Pour the Collodion

"The next proceeding is to clean a plate of glass thoroughly, finishing it with a piece of chamois skin or silk, and then to cover one side of it with the prepared collodion, which I do in the following way: -

I fasten a cylindrical piece of gutta percha to the under side of the glass as a handle; and, holding by this the plate in  my left hand in a level position, I pour on the collodion from a small phial, in a steady and uninterrupted stream, upon the near right-hand corner of the  plate, at the same time altering its level so as to cause the collodion to transverse the whole surface, and then allow  the superfluity to run back into the bottle from the furthest right-hand corner to the plate."

Create an even Coating

"Next, I immediately give the plate a rotatory motion by means of the gutta percha handle, to render the coating equal, and, after the expiry of from ten to fifteen seconds, according to the temperature, I immerse the plate slantingly in a bath of nitrate of silver, at a strength of 35 grains of the crystallized nitrate to 1 ounce of pure water."

"I suspend it in this bath for forty seconds without lifting it, and then raise and re-immerse it three or four times at short intervals, or until the solution flows freely over the surface and the solution is free from the streaky and greasy appearance that it has at first."

"The prepared plate requires now to be dripped for a short time, and then exposed to the image in the camera."

Work in a Darkroom

"The window of the room in which the plate is rendered sensitive  by the bath, and in which the picture is afterwards to be developed, &c., requires to be covered by a double layer of yellow calico."