American Dry Plates

AMERICAN DRY PLATES.

American dry plates are ready-sensitised ferrotype plates, and require no immersion in the silver bath. It is this class of plate which is used in the automatic machines. One of these, the " Quta," was illustrated the hypo. solution, and allow it to stand for a couple of clays. The clear liquid is then decanted, and forms the developer. It will keep for months if well stoppered, and can be used repeatedly. It is better, however, to keep the old solution in a separate bottle. The fixing solution con sists of 4 oz. of hypo. in 20 oz. of water. The time of exposure varies from half a second to about five seconds, or longer in dull weather. The developer is applied in the same way as with ordinary ferrotypes, and the plate carefully watched until the high lights and half lights are out and begin to blend. This will take from ten to twenty-five seconds, in moderately warm weather. The plate is then rinsed for a

on p. 47 ; another, which is a great favour ite with itinerant photographers, and is often met with at exhibitions, the " Taku quick," is shown by Fig. 188. The follow ing is a suitable developer :— Warm water... ... 1 quart Sodium carbonate ... lb.

Sodium sulphite ... lb.

llydroquinone oz.

Potassium bromide 100 grs.

Hypo-fixing solution ... 1 fluid oz.

First dissolve the carbonate and sulphite ; then add the hydroquinone and bromide. When these thoroughly dissolved, acid few seconds, and plunged at once in the hypo. Fixing is complete in from ten to thirty seconds, according to the tempera ture. The plate is again rinsed for a few seconds, and dried over a gentle heat, after which it may, if desired, be var nished.