Gelatino-bromide of Silver, Emulsion Process

In this process, the use both of the nitrate bath and of collodion are abolished.

The material employed is very troublesome to prepare, and on this account, as well as because of the risk of failure attending the use of the home-made article, it is far preferable it should be purchased. It may be obtained under the name of "Kennett's Sensitized Pellicle."

This pellicle consists of shreds of dry gelatine containing the sensitive salts.

Fresh directions accompany each packet of the " Sensitized Pellicle."

How To Clean Glass Plates

Mr. Mayall. Shake up together, alcohol 30 parts, strong liquid ammonia 10, water 40, and fine tripoli 30 parts. The plates are to be rubbed hard and evenly with balls of cotton wool dipped in this mixture. Rub again, when dry, with a clean ball of cotton; lastly, dust the back and edges with a clean hog's-hair brush.

How To Clean off Collodion Pictures

This may be done, whether they have been varnished or not, by means of a tuft of cotton wool dipped in wood spirit.

Cochineal Lake

Add 2 lbs. of pearlash to the red liquor from which the carmine has been prepared in the last process, and return it to the boiler with the dregs of the cochineal; boil for half an hour, draw the fire, and when the sediment has subsided, draw off the clear liquid into an earthem vessel. Pour on the sediment a solution of 1 lb. of pearlash in 2 gallons of water, and boil for half an hour. Filter, and return both liquors into the copper. When as hot as the hand can bear, add to the liquor, by little and little, 3 lbs. of powdered Roman alum, and let it simmer for 5 minutes. Allow it to settle, draw off the clear liquor, collect the sediment on a filter, wash it with clean rain-water, and leave it covered with a cloth for a few days, till half dry; form it into small lumps, and dry them in a stove.

Rose Pink

Boil 6 lbs. of Brazil-wood and 2 lbs. of peachwood in water, with 1/4 lb. of alum; and pour the strained decoction on 20 lbs. of sifted whiting.

Bistre

It is obtained from the soot of beech-wood.

Sap Green

The expressed juice of buckthorn-berries (and sometimes of other species of rhamnus, and also of privet berries) is allowed to settle, and the clear liquid evaporated to dryness. A little gum arabic is sometimes added to the juice.

The beautiful colours of the mauve series are prepared from coal tar by patented processes. Mineral Pigments. Azure Blue, or Smalts. The common is made by fusing zaffre (roasted cobalt ore calcined with siliceous sand) with potash. A finer quality is obtained by precipitating a solution of sulphate of cobalt by a solution of silicate of potash. Another cobalt blue is obtained by adding a solution of phosphate of soda to a solution of nitrate of cobalt, and mixing the precipitate, washed, but not dried, with eight times its weight of fresh hydrated alumina. When dry, heat it to a cherry red.

Egyptian Azure

Carbonate of soda 16 oz., calcined Hints 24 oz., copper fillings 4 oz. Pulverise, mix, and fuse in a crucible for two hours. When cold, reduce to powder.