A vert happy application has been made of collodion in photography. We do not expect to give here a treatise on this art, but we think it of interest to the reader to be informed of that part which specially treats of the application of collodion to the art.

Pure Cotton

Take wadding cotton, and treat it, 1st, with a solution of weak potash; 2d, with water; 3d, with hydrochloric acid; 4th, with boiling distilled water, and dry it.

Gun Cotton

. Take 10 ounces of dried nitrate of potash in fine powder, introduce it into a mortar, and pour on it 20 ounces of sulphuric acid. Mix well, and gradually immerse in the mixture 1 1/2 ounce of pure cotton. Leave the cotton a quarter of an hour; remove it to a funnel, and wash it well with lukewarm water. When the cotton is free from acid, wash it well three or four times with distilled water. Dry it at a proper temperature, keeping it covered with paper to keep off the dust. If during the process red vapors are evolved, the operation has to be begun over again.

Preparation Of The Collodion

It is better to prepare a large bottle at once, as it keeps well, and improves by settling. In a ground stoppered bottle introduce-

Rectified ether . . 100 parts (weight).

Commercial alcohol . 20 " "

Gun cotton • • • 2 to 4* "

Aq. ammonia . • 5 drops

* Use two parts in summer, and four in winter.

Shake occasionally, and when the cotton is dissolved, add -

Iodide of ammonium . . . 1 part Cyanide of potassium 1/10 "

Fluoride of potassium . . 1/10 "

When the salts are dissolved, filter through a cotton cloth into a bottle previously washed with ether. Instead of iodide of ammonium, you can use -

Iodide of potassium . . 1 part Iodine......2/10 "

The collodion has a yellow color, which after a few days becomes light straw.

As the solution of the salts is difficult in ether and alcohol, dissolve the salts in a few drops of water, and then add it to the collodion. For immediate use it should be kept in bottles of three or four ounces.

Cleaning Of The Glass

The glass, on which the collodion is applied, should be well cleaned with the following composition: -

Alcohol . . .10 ounces

Ammonia . . . 2 1/2 drms.

Rotten stone . . 1 1/2 drm.

Application Of The Collodion On The Glass

Take the glass by one corner, in the left hand, and with the right hand pour the collodion on to the centre of the glass and let it flow over the glass by giving it a half rotary motion. When the whole surface of the glass is covered, pour off the excess of collodion by the opposite corner, to prevent streaks, as you must only pour upon the glass enough to cover it. Place it horizontally, and give it a gently inclining motion from side to side. When the collodion begins to dry, immerse the glass plate into the sensitive bath.

Sensitive Bath Is prepared in the following manner: -

Distilled water . • . 100 parts Nitrate of silver . . . 8 "

Dissolve the whole of the silver in distilled water, filter, and let it stand a few hours. For this purpose use a vertical bath of gutta percha.

Before using the bath, filter the solution; when the bath is nearly full, immerse the plate quickly, raise it after a minute to inspect it, when it will have a milky color, nearly white, as well as an oily appearance caused by ether.

When these phenomena have disappeared, and the glass has no marble appearance, remove it; allow it to drain before putting it into the frame.

The length of time for it to remain in the bath of silver varies from one to three minutes. Expose the glass plate in the camera to take the picture. When done develop the image.