soap-crutching

from The Century Dictionary.

• noun The process of crutching or stirring soap in kettles.
• noun It consists of a vertical cylinder in which are numerous spiral wings and an upright shaft with radial arms, to which a rotary motion is communicated by gearing. When the tank is filled with soap, the spiral wings act like screws, carrying up the heavier part of the materials toward the top, and thoroughly intermixing the whole.