Understanding Fatty Acid Profiles
What every quality score in SoapMath actually measures — bar soap, liquid soap, and cosmetics
Where the Scores Come From
Every oil is a blend of fatty acids. When you combine oils with lye, those fatty acids saponify and their properties carry through to the finished soap. SoapMath calculates weighted averages across your whole oil blend to produce quality scores.
NaOH and KOH Use Different Scoring Models
NaOH produces a hard bar soap. KOH produces a soft paste or liquid soap. The quality concerns are different — a bar soap needs to unmold and last in a soap dish; a liquid soap needs to dilute cleanly and stay clear. SoapMath uses a separate scoring model for each, calculated from the same underlying fatty acid data.
The Core Fatty Acids
| Fatty Acid | Type | Found In | What It Contributes to Soap |
|---|---|---|---|
| Lauric (C12) | Saturated | Coconut oil, palm kernel oil | High cleansing, hard bar, fluffy lather — can be drying above 30% |
| Myristic (C14) | Saturated | Coconut oil, palm kernel oil | Similar to lauric — cleansing and lather |
| Palmitic (C16) | Saturated | Palm oil, lard, tallow, cocoa butter | Hardness and stable creamy lather in bar soap — drives Clarity Risk in liquid soap |
| Stearic (C18:0) | Saturated | Shea butter, cocoa butter, tallow | Hardness and creamy lather in bar soap — also drives Clarity Risk in liquid soap |
| Oleic (C18:1) | Monounsaturated | Olive oil, avocado, almond, apricot | Conditioning and mildness — moderately offsets Clarity Risk in liquid soap |
| Linoleic (C18:2) | Polyunsaturated | Sunflower, safflower, hemp | Conditioning and mildness — prone to rancidity at high levels |
| Linolenic (C18:3) | Polyunsaturated | Flaxseed, hemp, chia | Minor conditioning — highly prone to rancidity, keep below 5% |
| Ricinoleic (C18:1-OH) | Hydroxy acid | Castor oil only | Lather booster, mildness, conditioning — meaningfully offsets Clarity Risk in liquid soap |
NaOH Bar Soap Scores
Bar soap uses seven scores, each measuring a specific quality that affects skin feel, shelf life, and how the bar behaves in use.
| Score | Driven By | Target Range | What It Means |
|---|---|---|---|
| Cleansing | Lauric + Myristic | 12–22 | Degreasing power — above 25 becomes stripping for most skin types |
| Conditioning | Oleic + Ricinoleic + Linoleic | 44–69 | Skin feel after rinsing — higher means softer, less tight feeling |
| Bubbly Lather | Lauric + Myristic | 14–46 | Big, airy, quick-forming bubbles |
| Creamy Lather | Palmitic + Stearic + Ricinoleic | 16–48 | Dense, lotion-like lather that clings and rinses slowly |
| Hardness | Palmitic + Stearic + Ricinoleic | 29–54 | How quickly the bar unmolds and how long it lasts in a wet dish |
| Iodine Value | Unsaturated fatty acids | Below 70 | Higher = more unsaturation = faster rancidity risk |
| INS | SAP value − Iodine value | 136–165 | Single-number quality summary; 160 is often cited as ideal |
High Cleansing and Skin Feel
Coconut oil can push cleansing scores above 60 in a pure-coconut formula. Even at a 20% superfat, the bar will strip skin oils aggressively. Blend in conditioning oils or limit coconut to 25–30% to bring the score into a comfortable range.
Pro Tip
Castor oil (ricinoleic acid) at 5–8% boosts both creamy lather and conditioning without increasing cleansing. It's one of the most efficient bar-soap additives per gram.
KOH Liquid Soap Scores
Liquid soap has different quality requirements — it needs to dilute into water cleanly, stay clear, and feel mild on skin with frequent use. SoapMath computes five KOH-specific scores using a model built around these concerns.
| Score | Formula | Target | What It Means |
|---|---|---|---|
| Cleansing | Lauric + Myristic | 10–25 | Degreasing power — same fatty acids as bar soap, slightly lower typical target for liquid |
| Lather | Lauric + Myristic + Ricinoleic | 15–35 | Combined lather quality — includes ricinoleic's creamy boosting contribution |
| Mildness | Oleic + Ricinoleic + Linoleic | 50–75 | How gentle the soap feels during frequent daily use |
| Clarity Risk | (Palmitic + Stearic) − 0.25×Ricinoleic − 0.10×Oleic | Below 15 | Risk of haziness, cloudiness, or precipitation when diluted — the key liquid soap quality metric |
| Dilution Ease | Lauric + Myristic + Oleic + Ricinoleic | Higher ↑ | How smoothly the paste thins to a pourable consistency when water is added |
Clarity Risk — the Score That's Unique to Liquid Soap
Palmitic and stearic acids produce potassium soaps (potassium palmitate, potassium stearate) that are less soluble in water than their sodium counterparts. At high concentrations they create a hazy, whitish, or even flaky appearance once the paste is diluted. Ricinoleic acid (from castor oil) partially prevents this through its solubilizing properties — which is why liquid soap formulators add castor oil at 10–25%. The Clarity Risk formula in SoapMath weights ricinoleic's offset at 4× that of oleic acid, reflecting how much more effective it is at keeping the diluted soap clear.
Pro Tip
To lower Clarity Risk: reduce palm oil, lard, and tallow (high palmitic/stearic), and increase castor oil. A recipe of 50% olive + 30% coconut + 20% castor typically produces Clarity Risk scores well below 15 with good Mildness and Lather.
Dilution Ease Is Not the Same as Lather
Dilution Ease predicts how easily the soap paste thins with water — oils high in lauric, myristic, oleic, and ricinoleic all contribute to soluble soaps that dilute without clumping. A low Dilution Ease score means you'll need to work harder (diluting slowly with hot water) to get a smooth liquid. It does not predict how much the finished soap lathers.
How the Two Models Compare
| Quality Concern | Bar Soap (NaOH) | Liquid Soap (KOH) |
|---|---|---|
| Cleansing power | Cleansing score (12–22) | Cleansing score (10–25) |
| Skin mildness | Conditioning score (44–69) | Mildness score (50–75) |
| Lather quality | Bubbly + Creamy (two separate scores) | Lather score (single combined score) |
| Structure / solidity | Hardness score (29–54) | Not applicable — liquid soap is diluted to a pourable consistency |
| Shelf life risk | Iodine value (below 70) | Iodine value (same, but threshold is less critical for liquid) |
| Haziness / cloudiness | Not applicable | Clarity Risk score (below 15) — unique to liquid soap |
| Ease of dilution | Not applicable | Dilution Ease score (higher is better) |
| Overall balance | INS value (136–165) | Not used for liquid soap |
How Fatty Acids Behave in Cosmetics (Unsaponified)
Outside of soap, oils stay intact — their fatty acids act as emollients, barrier agents, and texture modifiers. The soap quality scores don't apply here.
| Fatty Acid | Cosmetic Role |
|---|---|
| Oleic (C18:1) | Penetrating emollient — absorbs quickly, good for dry skin, may clog pores for some skin types |
| Linoleic (C18:2) | Skin-identical lipid, barrier repair, anti-inflammatory — preferred for acne-prone skin |
| Lauric (C12) | Antimicrobial in anhydrous formulas — can feel heavy in emulsions at high levels |
| Palmitic / Stearic | Texture and consistency agents in creams and balms — add body and slip |
| Ricinoleic | Humectant-like, glossy finish — essential in lip products for glide |
Pro Tip
High-linoleic oils (rosehip, hemp, sea buckthorn) are often preferred for acne-prone skin over high-oleic options like olive or avocado. Linoleic acid is closer to what skin naturally produces in its surface lipid layer.
Troubleshooting
| If… | Then… | Solution |
|---|---|---|
| Hardness score is too low | Add more saturated fats — cocoa butter, palm, lard/tallow. Target hardness 50–70. Use sodium lactate 3% in water phase to speed initial set. | |
| Cleansing score too high or conditioning too low | Reduce coconut/palm kernel oil. Add olive, avocado, or sweet almond oil. Target cleansing below 18 for facial bars. | |
| Iodine value too high or antioxidant missing | Reduce high-linolenic oils (flax, hemp). Add ROE at 0.1% of oil weight. Store in cool, dry conditions. | |
| Clarity Risk score is too high — excess palmitic/stearic | Reduce palm oil, lard, or tallow. Increase castor oil to 15–25%. Dilute with warmer water. Check SoapMath Clarity Risk score — target below 15. | |
| Dilution Ease score is low | Increase lauric/myristic oils (coconut) and castor oil. Dilute paste slowly with hot water (about 140°F / 60°C) while stirring. | |
| Bubbly score too low — not enough lauric/myristic | Increase coconut oil to at least 20–25%. Add castor oil at 5–8% for creamy lather. |
See every score for your recipe in SoapMath
Switch between NaOH (bar soap) and KOH (liquid soap) modes — SoapMath calculates the appropriate score set for each in real time as you build your recipe.