Concerning the boiling of the soap, the saponification must be carefully carried out, as the high proportion of cocoanut oil may cause a violent reaction in the kettle causing it to boil over.
The method of procedure is the same as for a settled soap up to the finishing. When the mass is finally settled after the finish, the soap should be more on the "open" side, and the object should be to get as long a piece of goods as possible.
Due to its high melting point, a much harder crust forms on the surface of a floating soap and in a greater proportion than on a settled soap during the settling. In a large kettle, in fact, it has been found impossible to break through this crust by the ordinary procedure to admit the skimmer pipe. Much of the success of the subsequent operations depends upon the completeness of the settling, and in order to overcome the difficulties occasioned by the formation of the crust everything possible should be done in the way of covering the kettle completely to enable this period of settling to continue as long as possible.
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.