Selecting Oils for Soapmaking
Master SAP Values, Fatty Acid Profiles & Soap Qualities
Choosing the right oils is the foundation of great soap. Each oil brings unique properties: some create hard bars, others make fluffy lather, and some provide deep conditioning. The secret is understanding SAP values (how much lye each oil needs) and fatty acid profiles (what properties each oil contributes). This guide will teach you how to select and blend oils for perfectly balanced soap using the SoapMath soap calculator's database of 151 oils and fats.
The soap calculator includes FDA-compliant INCI nomenclature, precise SAP values for both NaOH and KOH, and calculates weighted soap properties based on your oil blend - taking the guesswork out of formulation.
Understanding SAP Values
What is SAP (Saponification Value)?
SAP value tells you exactly how many milligrams of alkali (lye) are needed to saponify 1 gram of that specific oil or fat. Every oil has a unique SAP value.
- NaOH SAP: For bar soap (solid lye)
- KOH SAP: For liquid soap (potassium hydroxide)
- Higher SAP = more lye needed per gram of oil
- Soap calculator does all calculations automatically
Why SAP Values Vary:
Different oils have different molecular weights and fatty acid compositions. This means each requires a unique amount of lye for complete saponification.
Example SAP Values (NaOH):
• Coconut Oil: 0.183 (needs more lye - high lauric acid)
• Olive Oil: 0.134 (needs less lye - high oleic acid)
• Castor Oil: 0.128 (needs least lye - ricinoleic acid)
Fatty Acid Profiles & Soap Properties
Each oil's fatty acid composition determines its soap characteristics. The calculator shows weighted averages based on your oil blend.
Cleansing Fatty Acids
Lauric Acid (C12) & Myristic Acid (C14)
- • Create fluffy, abundant lather
- • Very cleansing (can be drying in high amounts)
- • Found in: Coconut Oil, Palm Kernel Oil, Babassu Oil
- • Sweet spot: 15-30% of total oils for balanced cleansing
Hardness Fatty Acids
Palmitic Acid (C16) & Stearic Acid (C18)
- • Create hard, long-lasting bars
- • Stable creamy lather
- • Found in: Palm Oil, Tallow, Lard, Cocoa Butter, Shea Butter
- • Sweet spot: 30-45% of total oils for firm bars
Conditioning Fatty Acids
Oleic Acid (C18:1) - Monounsaturated
- • Creates gentle, conditioning soap
- • Stable lather with conditioning properties
- • Found in: Olive Oil, Avocado Oil, Almond Oil, Apricot Oil, Rice Bran Oil
- • Sweet spot: 40-60% for conditioning bars
Conditioning But Risky Fatty Acids
Linoleic Acid (C18:2) & Linolenic Acid (C18:3) - Polyunsaturated
- • Very conditioning, creates silky lather
- • Prone to oxidation → DOS (dreaded orange spots)
- • Found in: Sunflower Oil, Safflower Oil, Hemp Seed Oil, Flaxseed Oil
- • Limit to: <15% to prevent rancidity
Special Fatty Acid
Ricinoleic Acid (found in Castor Oil)
- • Creates stable, fluffy lather
- • Draws moisture to skin (humectant)
- • Use at 5-10% to boost lather in any recipe
- • Too much (>15%) = sticky, soft soap
Soap Properties (What the Calculator Shows)
The soap calculator calculates weighted soap properties based on your oil blend. Here's what each property means:
Hardness (29-54 = good range)
How firm your bar is. Too low = mushy soap, too high = brittle. Increase with palm, tallow, cocoa butter.
Cleansing (12-22 = good range)
Ability to remove oils. Too high = stripping/drying. Increase with coconut or palm kernel oil.
Conditioning (44-69 = good range)
How moisturizing it feels. Higher = gentler soap. Increase with olive, avocado, shea butter.
Bubbly Lather (14-46 = good range)
Big fluffy bubbles. Increase with coconut oil or add 5-10% castor oil.
Creamy Lather (16-48 = good range)
Stable, lotion-like lather. Increase with palm oil, lard, or butters.
Iodine (41-70 = good range)
Softness/conditioning. Higher = softer bar. Lower = harder, longer-lasting soap.
Oil Categories & Roles
Base Oils (50-70% of recipe)
Affordable, readily available, form the foundation.
- • Olive Oil: Gentle, conditioning, slow lather. Great for Castile soap (100% olive).
- • Palm Oil: Hardness + creamy lather. (Or sustainable alternatives: lard, tallow, babassu)
- • Coconut Oil: Hardness + cleansing + fluffy lather. Use 20-30% max to avoid drying.
- • Rice Bran Oil: Similar to olive, lighter feel, less expensive.
- • Canola/Soybean Oil: Budget-friendly, mild conditioning. Limit to 30%.
Luxury Oils (10-30% of recipe)
Special properties, label appeal, extra conditioning.
- • Shea Butter: Conditioning, hardness, creamy lather. Use 5-20%.
- • Cocoa Butter: Very hard bars, light chocolate scent. Use 5-15%.
- • Avocado Oil: Rich conditioning, green color. Use 10-30%.
- • Sweet Almond Oil: Gentle, conditioning. Use 10-25%.
- • Castor Oil: Lather booster, humectant. Use 5-10% (not more!).
Specialty/Label Appeal (1-5% of recipe)
Small amounts for marketing or therapeutic claims.
- • Hemp Seed Oil: Label appeal, conditioning. Limit to 5% (high linolenic = DOS risk).
- • Argan Oil: Expensive, great label appeal. Use 1-5%.
- • Rosehip Seed Oil: Skin benefits, beautiful pink tint. Limit to 3% (oxidizes quickly).
- • Neem Oil: Anti-bacterial claims. Use 1-3% (strong smell).
Popular Recipe Frameworks
Balanced Beginner Recipe
- • 35% Olive Oil (conditioning)
- • 30% Palm Oil, Lard, or Tallow (hardness + creamy lather)
- • 25% Coconut Oil (cleansing + bubbly lather)
- • 5% Castor Oil (lather boost)
- • 5% Shea Butter (luxury)
Gentle/Sensitive Skin
- • 50% Olive Oil (mild conditioning)
- • 20% Shea Butter (gentle hardness)
- • 15% Coconut Oil (lower for less cleansing)
- • 10% Sweet Almond Oil (extra gentle)
- • 5% Castor Oil (lather)
Vegan Palm-Free
- • 40% Olive Oil (conditioning base)
- • 25% Coconut Oil (hardness + lather)
- • 15% Cocoa Butter (hardness replacement for palm)
- • 10% Avocado Oil (conditioning)
- • 5% Castor Oil (lather boost)
- • 5% Shea Butter (conditioning)
High Lather/Bubbly
- • 40% Olive Oil (conditioning)
- • 30% Coconut Oil (big bubbles)
- • 20% Palm Oil (stability)
- • 10% Castor Oil (lather amplifier)
Using the Soap Calculator
Step 1: Choose Your Oils
- Browse 151 oils/fats with INCI names
- Enter percentage for each oil
- Total must equal 100%
Step 2: Review Soap Properties
- Calculator shows weighted soap properties (hardness, cleansing, conditioning, lather)
- Check fatty acid profile breakdown
- Adjust oil percentages to improve properties
Step 3: Set Lye Type & Superfat
- Choose NaOH (bar soap) or KOH (liquid soap)
- Set superfat (5% standard, 8-10% for dry skin, 1-3% for longer-lasting bars)
- Calculator auto-adjusts lye amount based on SAP values
Step 4: Get Your Recipe
- View complete recipe with precise measurements
- Print recipe with INCI ingredient list
- Save notes about fragrance, additives, pour temperature
Pro Tips & Common Mistakes
✓ Do This
- • Start with proven recipes, then modify small amounts
- • Always recalculate when substituting oils (SAP values differ!)
- • Limit polyunsaturated oils (<15%) to prevent DOS
- • Add ROE (Rosemary Oleoresin Extract) at 0.05% for shelf stability
- • Use distilled water to prevent mineral contamination
- • Cure soap 4-6 weeks for best results
✗ Don't Do This
- • Never substitute oils without recalculating lye (different SAP values!)
- • Don't exceed 30% coconut oil (very drying)
- • Don't use 100% soft oils without patience (needs 6-12 month cure)
- • Don't ignore DOS risk oils (sunflower, hemp >15% = problems)
- • Don't skip curing - fresh soap is harsh soap
Frequently Asked Questions
Related Resources
Tip: Use the Help Me Pick % Tool
After selecting your oils, use the Help Me Pick % tool in the Soap Calculator to automatically optimize oil percentages based on your hardness, cleansing, and lather preferences.