Free-hand crayons are made on Steinbach and other crayon papers, without any photograph as a basis. Silver enlargements are made on paper coated with a solution of chloride of silver, which the action of the light reduces to salts of silver. This is the oldest form of photography, and has been used since its introduction by Scheele in 1778. Silver enlargements are made by the aid of the sun (and are then called solar enlargements) or they can be made with the electric light.
Platinum enlargements are a recent advance in photographic printing with iron salts, the process which has been worked out and patented by W. Willis, Jr., being a development of such printing. Its principle is that a solution of ferrous oxalate in neutral potassium oxalate is effective as a developer. A paper is coated with a solution of ferric oxalate and platinum salts and then exposed behind a negative. It is then floated in a hot solution of neutral potassium oxalate, when the image is formed.
This process was first introduced by Mr. Willis in 1874, and he has since made improvements. He claims that the platinotype paper does not contain any animal sizing. The early experiments convinced him that the paper upon which the image was to be printed would prove an important factor, as all photographic paper contained animal sizing, which was found to be antagonistic to platinum salts. The action of platinum salts upon a paper containing animal sizing gave it a tint which no amount of acid washing could remove. For the past nine years Mr. Willis has had manufactured for his special use a Steinbach paper, free from the animal sizing, and he also uses a cold developer, thereby causing the paper to retain its original elasticity.
The chief points of difference between bromide enlargements and silver or platinum enlargements are that, in the former, we have the sensitive compound of silver suspended in a vehicle of gelatin, and, in the latter, a thin coating of an aqueous solution of the sensitive salts. In the former process, the image is not shown until the paper has been developed in the bath, while in the latter, the image is shown upon the paper when it is exposed to the light; so that, in the latter, the image or picture has only to be fixed or made permanent, while in the former, it is developed, then fixed. The gelatin bromide paper is coated with a solution of gelatin, bromide of potassium and nitrate of silver, developed with a solution of oxalate of potash, protosulphate of iron, sulphuric acid and bromide of potassium and water, and fixed with hyposulphate of soda. It is manufactured in America by E. and H. T. Anthony & Co. and by the Eastman Dry Plate Company.
CRAYON MATERIALS.
The following materials will be found necessary for crayon work:
A good photographic enlargement,
Easel,
Mahl stick,
Three inch magnifying glass,
Square black Conte crayon, Nos. 1, 2 and 3,
Charcoal holder for the same,
Hardmuth's black chalk points, Nos. 1, 2, 3, 4 and 5,
Holder for the same,
Box Faber's crayon points, Nos. 1, 2 and 3,
Holder for the above crayons,
Conte crayon, in wood, Nos. 0 and 1,
6 B. Faber's holder for Siberian lead pencil points,
4 H. Faber's holder with Siberian lead pencil point,
Velour crayon,
Peerless crayon sauce,
Black Conte crayon sauce, in foil,
White crayon, in wood,
Bunch of tortillon stumps,
Large grey paper stumps,
Small grey paper stumps,
The Peerless stump,
Large rubber eraser, 4 inches by 3-4 inches square, bevelled end,
Two small nigrivorine erasers,
Holder for " "
Piece of chamois skin,
Cotton batting of the best quality,
A sheet of fine emery paper,
A sharp pen knife,
One pound of pulverized pumice stone,
Mortar and pestle,
A large black apron,
Paste-board box about ten inches square and two inches deep,
Back-boards for mounting crayon paper and photographic enlargements,
Pliers,
Paste brush, three inches wide, to be used for starch paste or for water.
Experience has taught me that we cannot be too particular in giving directions as to the materials for our work, and therefore I have carefully included in the above list everything necessary to thoroughly equip the student. While the magnifying glass mentioned above is not an actual necessity, still a good one will be found very useful, as it will often show details in the photograph which would not be discovered by the naked eye. My male readers may at first object to so feminine an article as an apron, but it will be found thoroughly useful, and I am sure they will never consent to abandon it after they have once become accustomed to wearing it.