Skip to content

Understanding Soap Properties

soap-calc predicts the physical usage qualities of your soap based on the fatty acid profile of the oils used. These numbers are estimates, not guarantees, but are standard guideposts in the industry.

The Properties

Hardness

  • Description: Physical hardness of the bar.
  • Contributors: Saturated fats (Stearic, Palmitic, Lauric, Myristic).
  • Target Range: 29 - 54.
  • Low: Soft bar, melts fast. High: Very hard, brittle.

Cleansing

  • Description: Ability to strip oil from skin.
  • Contributors: Lauric, Myristic acids.
  • Target Range: 12 - 22.
  • Low: Very mild. High: Can be stripping/drying. Coconut oil is the main booster here.

Conditioning

  • Description: Emollient feel, ability to soothe skin.
  • Contributors: Unsaturated fats (Oleic, Linoleic, Linolenic, Ricinoleic).
  • Target Range: 44 - 69.
  • Low: Less moisturizing. High: Very soft, nourishing feel.

Bubbly

  • Description: Volume and fluffiness of lather.
  • Contributors: Lauric, Myristic, Ricinoleic.
  • Target Range: 14 - 46.

Creamy

  • Description: Stable, lotion-like lather.
  • Contributors: Stearic, Palmitic, Ricinoleic.
  • Target Range: 16 - 48.

Iodine

  • Description: Measure of unsaturation.
  • Target Range: 41 - 70.
  • Low: Hard bar. High: Softer bar, risk of rancidity (DOS).

INS

  • Description: Iodine, Saponification (derived number). Theory: Iodine - SAP = INS.
  • Target Range: 136 - 165.
  • Goal: ~160 is considered "ideal" per Dr. Robert McDaniel, but many great recipes fall outside this.