---
title: "What is a Soap made of?"
description: "Fats reacted with lye to make fatty acid salts — and most modern \"beauty bars\" are not soap at all. Every component, the material it uses, and the constraint that ma"
url: https://atoneplace.net/made-of/soap/
site: "At One Place"
---

# What is a Soap made of?

**What is a Soap made of?: Fats reacted with lye to make fatty acid salts — and most modern "beauty bars" are not soap at all.**

Saponification is one of the oldest chemical processes people run deliberately, and the reaction is irreversible — there is no free lye left in a properly made bar. The label is the giveaway for what you are holding: a product legally called soap lists sodium tallowate or similar, while a "beauty bar", "cleansing bar" or "facial bar" lists a synthetic surfactant and is not soap, because plain soap at pH 10 disrupts the skin barrier. Antibacterial soap is a separate question again: the US FDA banned triclosan and eighteen other antiseptics from consumer wash products in 2016 on the grounds that no benefit over plain soap had been shown.

## Component by component

*Every material is a choice, and the third column is the constraint that drove it.*

| Part | Material | Why that material |
| --- | --- | --- |
| the soap itself | sodium salts of fatty acids: sodium tallowate, sodium palmate, sodium cocoate | Each molecule has a water-loving end and an oil-loving end, so it lifts grease into water — the entire mechanism. |
| alkali | sodium hydroxide for bars, potassium hydroxide for liquid soaps | Potassium soaps are softer and stay liquid, which is the only real difference between bar and traditional liquid soap. |
| glycerin | a by-product of saponification, often removed and sold separately | Glycerin draws moisture to the skin; commercial bars often strip it out, which is why handmade soap feels less drying. |
| syndet bars | synthetic detergents such as sodium cocoyl isethionate | Real soap needs a pH around 9-10 to exist; a syndet bar can be made at skin pH, which is far gentler. |
| additives | fragrance, titanium dioxide for opacity, chelators such as EDTA | The chelator stops calcium in hard water reacting with the soap into scum, which is what leaves a ring in the bath. |

## Other around the house objects

- [Banknote](https://atoneplace.net/made-of/banknote/) — Cotton and linen rag paper, or polymer film — never wood pulp, which is why notes survive the wash.
- [Lego brick](https://atoneplace.net/made-of/lego-brick/) — ABS plastic moulded to a tolerance of about ten micrometres — the tightness of the fit is the whole product.
- [Toothpaste](https://atoneplace.net/made-of/toothpaste/) — Mostly abrasive and humectant, with a detergent for foam — the active ingredient is about 0.15% fluoride.
- [Coin](https://atoneplace.net/made-of/coin/) — Base-metal alloys chosen for wear and cost — most modern "silver" coins are copper-nickel and most "copper" ones are plated steel or zinc.
- [Sunscreen](https://atoneplace.net/made-of/sunscreen/) — UV filters — mineral, chemical or both — suspended in an emulsion whose job is to hold them in an even film.
- [Credit card](https://atoneplace.net/made-of/credit-card/) — Laminated PVC sheets 0.76 mm thick, carrying a silicon chip in epoxy and a copper antenna coil.
- [Candle](https://atoneplace.net/made-of/candle/) — Wax that is really a fuel, and a braided cotton wick that acts as a pump rather than as the thing burning.
- [Lipstick](https://atoneplace.net/made-of/lipstick/) — Castor oil carrying pigment, set into a stick with waxes — the oil is the workhorse, not the colour.
- [Shampoo](https://atoneplace.net/made-of/shampoo/) — Three-quarters water, a primary detergent, a milder secondary one, salt to thicken, and silicone to make hair feel smooth.
- [Balloon](https://atoneplace.net/made-of/balloon/) — Party balloons are dipped natural rubber latex; foil balloons are metallised plastic film and are not rubber at all.
- [Deodorant](https://atoneplace.net/made-of/deodorant/) — Deodorant kills the bacteria that cause the smell; antiperspirant uses aluminium salts to plug the sweat duct. Different products.
- [Toothbrush](https://atoneplace.net/made-of/toothbrush/) — Nylon filaments stapled into a polypropylene handle with a wire — three plastics that cannot be separated for recycling.

## Common questions

### What is a Soap made of?

Fats reacted with lye to make fatty acid salts — and most modern "beauty bars" are not soap at all.

### What is the the soap itself of a Soap made of?

Sodium salts of fatty acids: sodium tallowate, sodium palmate, sodium cocoate. Each molecule has a water-loving end and an oil-loving end, so it lifts grease into water — the entire mechanism.

### What is the alkali of a Soap made of?

Sodium hydroxide for bars, potassium hydroxide for liquid soaps. Potassium soaps are softer and stay liquid, which is the only real difference between bar and traditional liquid soap.

## Related pages

- [Banknote](https://atoneplace.net/made-of/banknote/)
- [Lego brick](https://atoneplace.net/made-of/lego-brick/)
- [Toothpaste](https://atoneplace.net/made-of/toothpaste/)
- [Coin](https://atoneplace.net/made-of/coin/)
- [Sunscreen](https://atoneplace.net/made-of/sunscreen/)
- [Credit card](https://atoneplace.net/made-of/credit-card/)
- [Candle](https://atoneplace.net/made-of/candle/)
- [Lipstick](https://atoneplace.net/made-of/lipstick/)
- [Pencil](https://atoneplace.net/made-of/pencil/)
- [Tennis ball](https://atoneplace.net/made-of/tennis-ball/)
- [Golf ball](https://atoneplace.net/made-of/golf-ball/)
- [Paper](https://atoneplace.net/made-of/paper/)
- [Glass](https://atoneplace.net/made-of/glass/)
- [Soccer ball](https://atoneplace.net/made-of/soccer-ball/)

## Sources

- Official vendor product documentation — At One Place (/about/)