WET COLLODION PROCESS We have now brought our historical sketch up to the time of the invention of wet-collodion process, which, as the one that has held the first place for a longer time than any other, and has kept it till within the last few years, deserves a somewhat more detailed account than those which went before it.
As we have said, the collodion process was invented by Mr. Archer. The novelties which this gentleman introduced may be stated as follows : He proposed glass as a support for the photograph instead of silvered copper or paper ; he proposed as a vehicle for the sensitive salts collodion, which is a substance obtained by dissolving gun-cotton or pyroxylin in a mixture of alcohol and ether ; and he proposed as a developer a solution of pyrogallic acid, or, as it is more properly called, pyrogallol, in water.
The results of the changes were that a very much briefer exposure than had been required before was sufficient, that either a positive or a negative picture could be got as was desired, and that there was more delicacy in the negative obtained than in that by the paper process, more boldness in a positive than in the Daguerreotype.
As in the last-mentioned process, the sensitive salts were iodide of silver and a small quantity of bromide.
Briefly described, the manipulations employed in the wet process are as follows : A glass plate is cleaned with great care. A short time before the exposure has to be made this plate is coated with what is known as iodised collodion,—that is to say, collodion in which is dissolved a certain quantity of soluble iodides and bromides. After the plate is held for a few seconds the collodion "sets" on its surface. Now the coated plate is dipped with great care into a vertical vessel containing a strong solution of silver nitrate, and known as the "bath." What is called "double decomposition" takes place, and iodide and bromide of silver are formed in the film. These are sensitive to light, and when the action has gone on for a few minutes the plate is ready for exposure. It is taken from the bath and placed in the camera whilst still wet in the manner which will be described for dry plates farther on. After exposure, and whilst still wet, it is treated with various different chemical substances, the operations being known as development, intensifica tion, fixing, washing, drying, and varnishing.
Now this process, although a beautiful one and a great advance on any which had gone before, left much to be desired, and this especially for the amateur and for the landscape photographer.
The operations which have been mentioned were very delicate and required no little manipulative skill; the solutions were expensive and were liable to go out of order ; especially the silver bath, the most expensive of all, was liable to the most extraordinary, unexpected, and inexplicable vagaries. Great has been the lamenta tion of many an amateur on suddenly finding that he could get on his plates no result but what is technically termed " fog," and that he would require to purchase many ounces of silver nitrate to make up a new bath.
Then there was the dirtiness of the process. All must remember well the bedabbled appearance of the person and possessions of the " wet-plate amateur." He was a terror to his friends. His silver solution appeared to produce every result but the right one. Its devastat ing effects were found in the most unexpected places. Clothes, carpets, and curtains alike suffered, and the stains produced were generally indelible ; but all these inconveniences were less than what resulted from the fact that the whole n of the plate had to be performed within the space of an hour or so,—that is to say, before the plate became dry. It was therefore necessary for the photographer, wherever he went, to burden himself with the whole of the apparatus and chemicals required to make and develop his plate ; and, as the manipulations could only he carried on in a yellow light, he had to carry with him in addition a tent in which to work. Besides this, the exposure, although shorter than what photographers had been previously used to, was generally inconveniently long. What are known as instantaneous effects could only be produced under the most exceptionally favourable circumstances, whilst the amateur was unable to satisfy his desire to portray the features of his friends unless he had the means of doing so in the open air. To take a portrait in an ordinary room required so prolonged an exposure that it was out of the question.