Soap Qualities Chart

What the numbers in SoapCalc mean, what ranges to aim for, and when to ignore them.

How Fatty Acids Shape Your Soap

Every oil in your recipe contributes a blend of fatty acids. Those fatty acids determine what your soap feels like, how it lathers, how hard the bar is, and how it treats your skin. SoapCalc shows you the combined result as seven "soap quality" numbers in the "All" column after you build a recipe.

The chart below shows which fatty acids contribute to which qualities:

Fatty Acid	Hardness	Cleansing	Bubbly Lather	Creamy Lather	Conditioning
Lauric	✓	✓	✓
Myristic	✓	✓	✓
Palmitic	✓			✓
Stearic	✓			✓
Ricinoleic			✓	✓	✓
Oleic					✓
Linoleic					✓
Linolenic					✓

Notice the pattern: saturated fats (lauric, myristic, palmitic, stearic) drive hardness and lather. Unsaturated fats (oleic, linoleic, linolenic) drive conditioning. Ricinoleic acid — unique to castor oil — is the oddball that contributes to lather, creaminess, and conditioning all at once.

The Seven Soap Qualities Explained

Hardness — Range: 29 to 54

How hard the finished bar will be. A harder bar lasts longer in the shower and holds its shape better. Driven by saturated fatty acids: lauric, myristic, palmitic, and stearic. The iodine value also affects hardness (see below) — lower iodine generally means a harder bar.

A bar on the low end of this range will be softer, may dent easily, and won't last as long. On the high end, you get a rock-solid bar that takes forever to wear down. Most soap makers aim somewhere in the middle.

Cleansing — Range: 12 to 22

How aggressively the soap grabs onto oils and washes them away. Here's what's actually happening: a soap molecule has one end that attracts water and another end that attracts oil. When you wash, multiple soap molecules surround a droplet of oil (along with whatever dirt it's carrying), latch onto it, and the whole cluster rinses away with water.

Lauric and myristic acids — the main fatty acids in coconut oil and palm kernel oil — produce soap molecules with a particularly strong oil-grabbing end. That's great for cleaning power, but too much of it strips the protective surface oils from your skin along with the dirt. That's why most recipes cap coconut oil at 30–35%. If you go higher, compensate with extra superfat (8–10%) to leave more conditioning oils on the skin.

Conditioning — Range: 44 to 69

How moisturizing the bar feels. Conditioning comes from the unsaturated fatty acids — oleic, linoleic, and linolenic — plus ricinoleic. These are the emollients that stay on your skin after rinsing. They help your skin retain moisture and keep it feeling soft.

Olive oil is the classic conditioning oil. A high-olive recipe (like 100% Castile soap) will score well above the suggested range for conditioning and well below for hardness and cleansing. It still makes beautiful soap. The numbers are guidelines, not boundaries.

Bubbly Lather — Range: 14 to 46

Big, fluffy, foamy lather. The kind of lather most people associate with soap. Driven primarily by lauric acid (coconut oil) and ricinoleic acid (castor oil). Higher bubbly numbers produce more voluminous foam. Lower numbers produce a denser, creamier wash with fewer bubbles.

If your soap doesn't lather much, it's usually because the recipe is low in lauric and ricinoleic acids. Adding 5–8% castor oil is the most common fix — castor boosts lather without adding cleansing the way coconut does.

Creamy Lather — Range: 16 to 48

The stability and thickness of the lather. Creamy lather is the dense, yogurt-like foam that stays put rather than sliding off your skin. Driven by palmitic and stearic acids — found in palm oil, tallow, lard, cocoa butter, and shea butter.

Bubbly and creamy tend to work against each other. Push bubbly up and creamy drops. Push creamy up and bubbly drops. The balance between the two is a matter of personal preference. Some people love a big bubbly lather. Others prefer a rich, dense cream. Most recipes aim for some of both.

A soap made entirely from oils that contain no lauric, myristic, or ricinoleic acids (like a recipe of only olive, palm, and shea) will produce a purely creamy lather with no bubbles at all. It still cleans. It just doesn't foam.

Iodine — Range: 41 to 70

The combined iodine value for your recipe. This measures the degree of unsaturation in your oil blend. Lower iodine = more saturated fat = harder bar. Higher iodine = more unsaturated fat = softer bar, more conditioning.

Recipes with iodine values above 70 tend to produce a soft bar. Above 90 or so, shelf life becomes a concern — highly unsaturated oils are more prone to rancidity (dreaded orange spots). It's not a hard cutoff, just a trend to be aware of.

INS — Range: 136 to 165

A composite number that predicts the overall physical quality of the soap bar. It was introduced by Dr. Robert S. McDaniel in his book Essentially Soap. The name stands for "Iodine 'n' SAP" — it's derived from the iodine value and the saponification value of the oils in your recipe.

An INS of 160 is often cited as the "ideal." A range of about 136–165 is generally considered good. But treat it as one data point, not a pass/fail test. 100% olive oil soap has an INS around 105. 100% coconut oil soap has an INS around 258. Both are legitimate soaps that people have made and loved for centuries. The INS value is useful for getting a quick read on a recipe's overall balance, not for declaring a recipe good or bad.

If your INS value is outside the range, don't panic. Check the individual qualities instead. A recipe with an INS of 120 but balanced hardness, conditioning, and lather might make a better bar for your skin than a recipe that hits 160 but is too cleansing. The individual qualities tell you more than INS alone.

Quick Reference

Quality	Suggested Range	What It Means
Hardness	29 – 54	Higher = harder bar, lasts longer
Cleansing	12 – 22	Higher = strips more oil, can be drying
Conditioning	44 – 69	Higher = more moisturizing
Bubbly	14 – 46	Higher = more fluffy foam
Creamy	16 – 48	Higher = denser, more stable lather
Iodine	41 – 70	Lower = harder bar
INS	136 – 165	Overall balance indicator (160 is "ideal")

The Honest Truth About These Numbers

Every beginner obsesses over hitting the suggested ranges. Every experienced soap maker eventually stops worrying about them.

The ranges are useful as training wheels. They'll keep you from accidentally making a bar that's unusably soft or painfully drying. But once you've made a dozen batches and started developing preferences, you'll find that the best soap you make might land outside the "ideal" range on two or three qualities.

Two classic examples that break the rules:

100% lard soap. Scores outside several suggested ranges. Makes an excellent, hard, creamy bar that's been a household staple for centuries. Traces quickly and can volcano if the fat is too hot, so it takes a little experience.

100% olive oil soap (Castile). Hardness, cleansing, and bubbly all fall below the suggested ranges. INS is around 105 — well below the 136–165 "ideal." Yet it's one of the most popular soaps in history. It cures into a hard, mild, conditioning bar if you wait 6+ months.

The numbers are a starting point. Your hands and your skin are the final judge.

To see the fatty acid profile of every oil in the SoapCalc database, check the oil chart. To build a recipe and see these qualities calculated live, open the calculator.