LIGHT OR FLUFFY POWDERS.
Light or fluffy powders containing 35-45% moisture can be made in two ways. The first method requiring a minimum equipment is to mix the powder and sal soda in a mixer, allow it to stand in frames for a week to crystallize or spread it on the floor for a few hours to dry and then grinding it.
The continuous method finishes the powder in a few minutes and with a minimum amount of labor. By this process the various ingredients, soap, soda ash solution, etc., are measured, run by gravity into the mixer, mixed and the molten mass run over the crystallizer or chilling rolls thru which either cold water or brine is pumped. From the roll the powder is scraped off clean by a knife, passes to a screen which sends the tailings to a grinder, falls into a storage bin from whence it is weighed and packed by an automatic weighing machine into cartons made up in most cases by another machine. Due to the large percentage of moisture contained in these soap powders the carton is generally wrapped in wax paper to aid in the prevention of the escape of moisture.
Scouring Powders.
Scouring powders are very similar to soap powders and differ only in the filler used. We have already considered these fillers under scouring soap, from which they do not differ materially. They are usually insoluble in water to aid in scouring. The mixer used for substances of this kind in incorporating the soap and alkali must be of strong construction.