Guides
Soapmaking guides
One question each, answered in the first paragraph, with sources and a worked example you can open in the free lye calculator.
- How do you calculate lye for soap?
Multiply each oil's weight by its SAP value, add the results, take off your superfat, and divide by the purity of your lye: that is the lye to weigh.
- Water as % of oils, lye concentration or water : lye ratio: what's the difference?
All three describe the same thing, how much water dissolves the lye; they just measure it against different things.
- What is superfat (lye discount) in soap?
Superfat is the share of the oils you deliberately leave unsaponified, by using less lye than would turn every gram of oil into soap.
- How do you make goat milk soap: replacing water with milk
Work out the recipe as if you were using water, then use the same weight of goat milk in place of some or all of that water.
- How much fragrance or essential oil should you use in soap, and what is IFRA?
Fragrance suppliers commonly suggest about 3–6% of the oil weight (roughly 0.5–1 oz per pound of oils) for cold process soap, as a starting point for scent strength, not a safety limit.
- Is handmade soap a cosmetic? US labeling rules for soap (CPSC vs FDA)
In the US, a bar is regulated as "soap" by the Consumer Product Safety Commission only if it is mainly fat-and-alkali soap, gets its cleaning from that soap, and is sold only as soap.
- What are INCI names, and how do you use them for handmade soap?
INCI names are the standard ingredient names used on cosmetic labels, such as Olea Europaea Fruit Oil for olive oil or Sodium Hydroxide for lye.
- How long does cold process soap need to cure?
Most cold process soap is cured for about 4 to 6 weeks, and soaps very high in olive oil, such as castile, are often cured much longer.
- Why do soap calculators give different numbers?
Usually because the calculators aren't being asked the same question: a different superfat, lye purity or water setting is the most common cause.
- How do you price handmade soap?
Start from what one bar really costs you: the ingredients for a batch divided by the bars you cut, plus packaging, a wage for your time and a share of overhead.
Comparing tools? See Soap Ledger compared with other soap calculators and apps.