Lyes and fats must be weighed on a scale and not judged by a volume measuring cup. Plastic wrap is better for lining the molds than shortening or grease, and distilled water is preferred over tap or hard water. It's necessary to be patient with the curing, which can take up to six weeks. Sometimes the smells can be so strong, it's better to work outside. Milk instead of water can make a creamier soap.
Essential oils work best as additives.
Howard cautions again that when a soapmaker wants to be creative he or she must be certain the oil or fat being added is meant to go on the skin. For instance, some potpourri oils are not. She insists that soaps be tested for their PH balance after the batch is cured and discarded if the balance is over 9, which is too harsh. If it's between 7.5 and 8.5, it's just right, she said. Howard said glycerine is more valuable to the explosives industry than to soap manufacturers, so soaps are left too dry as the glycerine is mostly poured off and sold.