Soap Quality Calculator — Blend Indices

A soap quality calculator on this page models four oils—coconut, olive, castor, and shea—as percentages of total oil weight. It outputs a weighted INS (a traditional index often linked to bar firmness in textbook charts) and three tendency scores for cleansing, conditioning, and bubbly lather, scaled for quick comparison. The math uses published-style property numbers for each oil and blends them by percentage—similar in spirit to hand-calculating a weighted average before you pour. It is an educational screen for comparing recipes, not a certificate of cosmetic efficacy.

Handmade soap depends on trace speed, hardness, lather, and feel—numbers do not capture romance, but they turn “too cleansing” into a comparable score. Pair indices with recipe optimization and process notes so oil changes show up on paper before you scale.

Weighted INS (simplified): For each oil, multiply its typical INS by (that oil’s percent ÷ 100). Add the contributions. Example: 40% coconut (INS ~258) contributes 103.2; 30% olive (~105) contributes 31.5; sum all four for a blend INS near the ranges you see in charts.

Tendency scores: Same pattern—each oil brings cleansing, conditioning, and bubbly contributions; multiply by percent of recipe and add. This page normalizes some columns to a 0–100 style scale so different recipes sit on one chart.

Manual check: Change only one oil’s percent, re-sum to 100%, and see whether INS moves in the direction you expect (more coconut usually raises cleansing and INS in many models).

At the default 35/30/25/10 split, note INS and tendency scores, then nudge coconut down two points and shea up two—watch how cleansing and conditioning scores trade places before you touch oils. That single-variable discipline beats random tweaks.

Lock percents here, translate to gram oils via total batch size, then run the soap calculator. After cure, compare shower notes to the index prediction; when they disagree, log pour temperature and fragrance before you blame the oils.

Spa line vs kitchen line: Compare two blends with the same superfat; the “spa” recipe might trade coconut for more shea to lower cleansing tendency on paper—then you verify skin feel after six weeks. Teaching: Show students how castor bumps bubbly score without always matching a huge jump in cleansing. Wholesale: When a buyer asks for a “harder” bar, INS and hardness tools give a first-pass answer before you reformulate palm or cocoa content.

• Treating scores as legal or medical claims — they are formulation comparisons only.
• Ignoring process — water discount and fragrance can dominate trace even when indices look mild.
• Using only four oils in real life — the model is fixed; add other oils in your own spreadsheet with SAP and property data.
• Skipping cure — a “good” index does not guarantee a lovely bar at day three.

Cross-check with soap hardness (INS-style blend view) and soap lather for multi-angle review. Log scores in the same row as batch ID, pour temperature, and fragrance lot. When numbers disagree with your hands, trust your hands—but investigate process before you rewrite oils. For production scaling, combine indices with batch size math so percentages stay locked.

Water phase, gel, honey, milk, and fine fatty acid differences are not fully modeled here—pair numbers with process notes and cure tests.

See what soap quality charts and INS-style numbers mean and how recipe formulation ties oils to those scores.