Originally Posted by
mtwoodwrkr
The excerpt below, from Shaving 101 at shaving101.com, is the best explanation I know. Hope this helps.
"Triple milling is a manufacturing process that soap makers use to make their products dense and uniform so that they lather better and last longer. A manufacturer uses a special machine to shred and roll the soap until it becomes a smooth paste-like substance. This milling process is repeated three times before the soap is finally molded and allowed to finish the curing process. By doing this, the manufacturer is able to ensure that every puck of soap from the batch is uniform in texture, and that the lather created with its first use is consistent until its last use."