Collodio-Chloride Papers

A collodion printing-out paper was introduced as early as 1865, by Mr. G. Wharton Smith, but gradually fell into desuetude, partly owing to difficulties of manufacture, partly because the thoughtless habit of breaking the grain of papers, in order to make them lie flat after first drying, produced ugly cracks on the surface. It has lately been revived, and, if treated with care, the exquisite surface and delicacy of detail characteristic of this paper should render it once more popular. It is not easy to prepare, since from unknown causes the nitrates, especially nitrate of silver, separate from the emulsion and crystallise on the surface. Sir W. Abney has proposed the following emulsion through which he afterwards passes ammonia to form ammonium nitrate, adding afterwards a small quantity of silver nitrate in the proportion of about eight grains to the ounce of emulsion.

1. Silver Nitrate........ 1 dr.

Water (distilled)........ 1 „

2. Strontium Choride....... 64 gr.

Alcohol......... 2 oz.

3. Citric Acid......... 64 gr.

Alcohol......... 2 oz.

To every two ounces of plain collodion add thirty drops of No. 1, previously mixed with 1 dr. of alcohol; then add 1 dram of No. 2 shaking well; lastly half a dram of No. 3. In a quarter of an hour it is fit for use.1

1 Note. - Instruction in Photography. p. 529. 1905 Edition; Legros Autotypie. Paris 1887.

The collodio-chloride papers may be toned in the same baths as gelatine papers, and may also be developed. But the caution about observing makers' formulae is even more important, the necessary proportion of gold varying with each emulsion.

Albumen Paper

For some purposes, and especially for good plucky negatives, albumenised paper is to be preferred to gelatine paper. The detail in the shadows is far superior and the toning process seems to go on more smoothly with less danger of double tones. The chief disadvantages are that it does not keep well after sensitising, and that, if an excess of albuminate of silver is formed, the print is liable to fade. But the latter defect will not arise, if there is sufficient of soluble chloride salts mixed with the albumen, the chloride of silver forming much more rapidly than the albuminate.

Albumenising The Paper

It is usual to take fresh eggs for the albumen, though some assert that stale shop eggs give a brighter and more even coating. A large English egg will yield an ounce, foreign eggs from 5/8 to 7/8 of an ounce, of albumen. Take:

Ammonium or Sodium Chloride . . . . 80 gr.

Spirits of Wine.......2 dr.

Distilled Water.......2 oz.

And when these are dissolved add 7 oz. albumen, and beat up with quills or an egg whisk for about 20 minutes. Filter through a sponge or wad of cotton-wool and the mixture may then be poured into a flat dish.

Take the paper (Saxe or Rive is the best) and holding it by two opposite corners, so bend the sheet that the middle first touches the albumen. Spread carefully on the surface, taking care that none flows over the edges on to the back of the paper. After about a minute lift up the paper very gradually by one corner. If there are bubbles, break them with a camel-hair brush, and float it again until a uniform coating is secured. Then hang it up by two clips in some dry place, where it will not be exposed to dust. Double albumenised paper is made by drying on a bath of spirit and then re-coating with the same mixture as before. The proportions given will coat about a quire of paper.

The Sensiting Bath

Ready-coated albumen paper is still kept in stock by the leading firms, both in the unsensitised and sensitive states; but the latter should only be bought when guaranteed fresh, and must be quickly used. The paper may be sensitised at home by making up the following bath:

Nitrate of Silver.......I oz.

Sodium Nitrate (pure)......1/2 ,,

Loaf Sugar........30 gr.

Water.........12 oz.

Float the paper, albumenised side downwards, on this bath in just the same way as was directed above for the albumenising process. Lift the corners one by one, and break any air bells that may be formed with a glass rod. Float for about four minutes, then hang up once more by clips to dry, but this time away from any actinic light. Rapid drying in a warm cupboard will preserve the brilliancy of the surface. The above bath is calculated for the use of amateurs, who will only have a few sheets to sensitise. For larger quantities, the bath recommended by Mr. H. N. King is one of the best. Prepare two separate solutions.

A. Nitrate of Silver...... 2 oz.

Sodium Nitrate (pure) . . . . . . 1 „

Loaf Sugar........ 50 grs.

Water......... 25 oz.

B. Nitrate of Silver....... 2 oz.

Sodium Nitrate...... 1 "

Loaf Sugar........ 60 gr.

Water......... 10 oz.

Use Solution A with about 1/4 oz. Solution B, for sensitising the first four sheets of paper. After every four sheets add about 1/4 oz. of Solution B, rock the whole well, and proceed to sensitise the next 5 sheets, and so on. By this means the bath will be always kept at about the same strength. Dust and scum on the surface of the bath may be removed by drawing a piece of pure chemical blotting paper or filter paper across the surface. A little kaolin kept in the bottle will always keep it clear. If the paper is required to be kept for some time it is usual to draw it slowly through distilled water to which a little citric acid has been added.

Measles

A disagreeable outbreak after printing of red spots, which do not tone to the same colour as the rest of the print, is known as "measles." It is generally attributed to the lack of any substance with which the chlorine can combine when liberated from silver chloride during printing. Hence it attacks the albuminate. There should be a little free nitrate of silver left in the paper by the sensitising process. Paper that has been acidified for keeping purposes should be exposed to the fumes of 880 ammonia before printing. Or such paper may be kept between sheets of blotting-paper, which have been dipped in a 5 per cent. solution of potassium nitrite and then dried. Albumen paper should always be kept under pressure until time of using, and in hot climates must not be allowed to get too dry.