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water, solution, grains, paper, lac and added

COOPER'S PROCESS.—A printing process, the invention of Mr. Henry Cooper The basis of the process lies in the substitution of a resin or substance of a resinous nature, in the place of albumen or other sizing matter. Prints obtained by this process have a more artistic appearance than pictures printed upon albumenised paper, and they are devoid of inartistic gloss. The two formulas given were communicated to Captain Abney by the inventor.* Frankincense to grams Mastic. 8 grains Calcium chloride 5 to to grains Alcohol. ounce As soon as the resins are completely dissolved in the alcohol, the paper to be prepared is mmersed in the solution, and then taken out, dried and rolled. It is best to hang the paper in frying, and to increase the temperature of the room to about 8o deg. Fahr The sensitizing silver bath recommended is made up as follows: Silver nitrate Go grains Water . ounce To the water as much gelatine should be added as possible without gelatinizing at io deg. Fahr.

The second formula alluded to gives very fine prints, remarkable for their softness and lelicacy of gradation of the half tones.

A suitable paper is first prepared by coating with an emulsion of white lac in gelatine. Phis is prepared by dissolving three ounces of fresh white lac in a pint of strong alcohol :t is important that the lac be fresh, as on exposure to the air it becomes insoluble after a time. Nhen dissolved it is filtered and decanted, and as much water added as it will possibly bear vithout precipitating the lac. To find out the largest quantity of water permissible, take a given of the solution in a test tube and add water minim by minim until the lac is precipitated. careful calculation will then show how much water to add to the bulk of the solution, which vill, of course, be under the amount required for precipitation.

One ounce of good hard gelatine is next soaked in a pint of cold water, and vhen soaked the temperature is raised to between i8o to zoo deg. Fahr., when the lac

olution is added, constantly agitating the solution the while. It sometimes happens that at this tage the gelatine becomes precipitated. A little hot water should at once he added. The pint If lac solution should, however, be emulsified in the gelatine solution.

To prepare the paper, the emulsion is just warmed and placed on a flat dish, and the paper ither immersed in or floated on the solution for about three minutes. It is then hung up to dry. Vhen dry, the coated surface is floated for about two minutes on Ammonium chloride to grains Magnesium or ammonium lactate io grains t is again put away to dry, when it is ready for sensitizing, which should be done on a Moderately strong bath. This will answer well: Silver nitrate so grains Distilled water. ounce To obtain a great amount of vigor in the prints, they may be floated on Citric acid 5 grains White sugar 5 grains This bath will be found to improve by use, due in all probability to its absorbing silver nitrate from the paper after sensitizing.

Cooper's toning formula is the following: Gold trichloride 2 grains Precipitate chalk (pure) a pinch Hot water to ounces Two drachms of sodium acetate are placed in the stock bottle, and this solution filtered on to it. Water is then added to make up to 20 ounces, and in a few hours the solution is ready for use. It improves by keeping, however.

In toning, place a few ounces of water in the dish, and add an equal quantity of the stock solution. The prints are then laid in, and if the toning process is slow, some more of the solution is added. Over-toning is to be avoided in this process. Fixing is done with sodium hyposulphite in the usual manner.