The three roll mill is used in soap manufacturing to refine the soap. A roll mill is composed with three rolls that rotates with different speed. The rolls are cooled by means of a water chiller to avoid a production rate reduction. The most important parameter of a soap roll mill is the gap of the two last rolls; usually a gap of 0.15 or 0.20 mm is advisable for standard soap. The increasing or decreasing of the gap is linked to the production rate of the soap roll mill.
The mainly strength of a roll mill is the ability to destroy the dry specks inside the vegetables soap noodles. This work is difficult to be obtained with a refining plodder. Depending from the formula, many times a roll mill is used. instead of a refining plodder, in the manufacturing of synthetic soap.
In the past a roll mill with 4 and 5 rolls was used, but in the last decades these machines disappeared. The final soap coming out from a roll mill is called soap flakes.