Where in cold process soap, the saponification process takes 24-36 hours to complete, with hot process, the saponification is done when the soap is done cooking. It may seem an odd addition of extra work...but there are a couple of benefits of hot process soap:
- Since you add fragrance and additives after the soap has cooked, they do not come in contact with the lye. This can be more gentle on fragile fragrance oils, and can reduce the lye’s effect on botanicals like flower petals and lavender buds which turn brownish black when they contact the lye.
- The soap is ready to use sooner – the process cuts a day off of the saponification process and (depending on how much water you use in your recipe) can cut down on the cure time needed
- The soap has a rougher, more rustic look to it – which can be desirable with some soap recipes.
You can use pretty much any soap recipe to make hot process soap. The only caveat is that you want to use the full amount of water. Since you're going to be cooking the soap, some of the water evaporates...so you don't want to skimp.
For this recipe, which made about 4.5 pounds of soap, I used:
- coconut oil – 14.6 oz. – 30%
- olive oil – 13.7 oz. – 28%
- lard – 11.7 oz. – 24%
- almond oil – 3.9 oz. – 8%
- castor oil – 2.4 oz. – 5%
- cocoa butter – 2.4 oz. – 5%
- 6.8 oz. lye – 6% lye discount
- 17 oz. water – (no water discount)
- 2 oz. of fragrance or essential oil
- 2 tbs. of rhassoul clay
- 1/2 tsp. of green oxide
- 1 tsp. of silver mica