This apparatus is principally valuable in dealing with large quantities, since it saves a great deal of labor, and affords perfect certainty of the emulsion being well washed. It may not be unnecessary to maintain that the difficulties of perfect washing--particularly if one do not wash with running water--increase at least in quadruple proportion to the quantity of emulsion manipulated.--Franz Stoke, Ph.D., in Br. Jour, of Photography.
HOW TO MAKE EMULSION IN HOT WEATHER.
By A. L. HENDERSON.
Numerous complaints have reached me within the last few weeks of the difficulty experienced in preparing emulsion and coating plates; one is very likely to blame everything but the right, but doubtless the weather is the culprit.
I have always held that to boil gelatine is to spoil it, and, even when emulsification is made with a few grains to the ounce and cooled down before adding the bulk, the damage is done to the smaller quantity, so that when mixed it contaminates the whole mass; moreover, it is impossible to set and wash the gelatine without the aid of ice.
I have lately made several batches (with the thermometer at 92° in the shade, and the washing water at 78°) as follows:
Hard gelatine...............,...... ½ ounce.
Water.............................. 2 ounces.
Alcohol............................ 2 "
Bromide ammonia....................150 grains.
Liquor ammonia, 880................ 60 drops.
When all is thoroughly dissolved and of about 120° temperature, add, stirring all the time,