NaOH Needed
76.95 grams
Water
156.2 grams
Total Oils
550.0 grams
NaOH Needed
76.95
grams
Water
156.23 grams
Total Oils
550.00 grams
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Inputs
Result
Total lye = (300 × 0.134) + (150 × 0.178) + (100 × 0.141) = 40.2 + 26.7 + 14.1 = 81.0g. After 5% superfat: 81.0 × 0.95 = 76.95g NaOH. Water = (76.95 / 0.33) - 76.95 = 233.18 - 76.95 = 156.23g.
Inputs
Result
Total lye = (400 × 0.134) + (200 × 0.128) = 53.6 + 25.6 = 79.2g. After 8% superfat: 79.2 × 0.92 = 72.86g. Rounded to 72.86g NaOH. Water = (72.86 / 0.30) - 72.86 = 242.87 - 72.86 = 170.01g. (Values may differ slightly due to rounding at each step.)
Saponification is the chemical reaction between fats/oils and lye (sodium or potassium hydroxide) that produces soap. Each oil has a specific SAP value that determines how much lye is needed.
Superfat (or lye discount) is the percentage of oils that remain unsaponified in the final soap. Typically 5-8%, it makes soap more moisturizing and ensures no excess lye remains.
| Superfat % | Soap Feel | Hardness | Best For |
|---|---|---|---|
| 3% | Firm, cleansing | Hard | Laundry/utility soap |
| 5% | Balanced | Medium-hard | Everyday body bars |
| 7–8% | Moisturizing | Medium | Sensitive skin, face bars |
| 10%+ | Very conditioning | Soft | Specialty/shampoo bars |
Sodium hydroxide (NaOH) creates solid bar soap, while potassium hydroxide (KOH) creates liquid soap. KOH requires about 40% more than NaOH for the same amount of oils.
| Property | NaOH (Sodium Hydroxide) | KOH (Potassium Hydroxide) |
|---|---|---|
| Soap type | Hard bar soap | Liquid/cream soap |
| Amount needed | Base amount | ≈40% more |
| Cost per lb | $3–$5 | $5–$8 |
| Cure time | 4–6 weeks | 1–2 weeks (paste) |
| Purity | 97–99% | 90% (adjust in calc) |
Most soap makers use 28-33% lye concentration. Lower concentrations (more water) give more time to work but longer cure times. Higher concentrations speed up trace and curing.
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Last Updated: Mar 26, 2026
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