When the soap is finished it is run into a specially constructed U-shape crutcher, a Strunz crutcher is best adapted to this purpose, although a rapidly revolving upright screw crutcher has been found to give satisfaction upon a smaller scale, and a sufficient quantity of air beaten into the soap to make it light enough to float. Care must be taken not to run the crutcher too rapidly or the soap will be entirely too fobby. During this operation the mass of soap increases in bulk, and after it has been established how much air must be put into the soap to satisfy the requirements, this increase in bulk is a criterion to estimate when this process is completed. It is of course understood that the longer the crutching continues the greater quantity of air is incorporated and the increase of volume must be established for a particular composition by sampling, cooling the sample rapidly and seeing if it floats in water. If the beating is continued too long an interval of time, the finished soap is too spongy and useless. The temperature of the mass during crutching is most important. This must never exceed 158 degrees F. At 159 degrees F. the operation is not very successful, yet the thermometer may indicate 140 degrees F. without interfering with this operation. If, however, the temperature drops too low, trouble is liable to be met with, by the soap solidifying too quickly in the frames. When the crutching is completed, the soap is allowed to drop into frames through the valve at the bottom of the crutcher and rapidly crutched by the hand in the frames to prevent large air spaces and then allowed to cool. It is an improvement to jolt the frames as they are drawn away as this tends to make the larger air bubbles float to the surface and thus reduce the quantity of waste. When the soap has cooled, the frame is stripped and the soap slabbed as usual. At this point a layer of considerable depth of spongy soap will be found to have formed. This of course must be cut away and returned to the kettle. The last few slabs are also often rejected, inasmuch as the weight of the soap above them has forced out so much of the air that the soap no longer floats. As a fair average it may be estimated that not more than 50 to 60 per cent. of the soap in the kettle will come out as finished cakes. the remaining 40 to 50 per cent. being constituted by the heavy crust in the kettle, the spongy tops, the bottom slabs and scrapings. This soap is of course reboiled and consequently not lost, but the actual cakes obtained are produced at a cost of practically double labor. It is advisable to add a small quantity of soap blue color to the mass while crutching to neutralize the yellowish tint a floating soap is liable to have. Some manufacturers add a percentage of carbonate of soda, about 3 per cent., to prevent the soap from shrinking. Floating soap may also be loaded with sodium silicate to the extent of about 5 per cent. TOILET SOAP.