Why Is Ethanol Used to Make Soap?

Saponification is the process of making soap from sodium hydroxide--also known as lye--and fat. Soapmakers add ethanol to hard soap batches to better mix the soapmaking materials during the saponification process. It is a vital additive for attaining the most clarity in transparent glycerin soap. Ethanol can be a dangerous soapmaking material, so some home soapmakers choose substitutes.

Ethanol is a solvent used in soapmaking. Also called ethyl alcohol or grain alcohol, ethanol is colorless and highly flammable. Ethanol is made from the fermentation of carbohydrates like potatoes and sugar.

Though some types of ethanol are drinkable, some ethanol is denatured to make it non-drinkable. Many soapmakers avoid denatured alcohol because it contains odorous or toxic additives that can affect the soap.

Using ethanol in the soapmaking process generally creates soap with a see-through, glass-like look, especially with glycerin soap. The higher the proof of the alcohol, the more transparent the soap. Proof is the unit of measurement used to identify the potency of alcohol; one alcohol percentage equals two proof. Ethanol used to make transparent soap should be around 180 proof, or 90 percent alcohol.

Ethanol is used in the process of making bars of hard soap. Ethanol helps the chemical reaction between the sodium hydroxide solution and the melted fatty oils. It is most often used when making glycerin soap. Soapmakers manufacturing non-transparent soap may substitute the more budget-friendly isopropyl alcohol to replace up to a third of the ethanol used in the soapmaking process.

Ethanol is dangerous because it is explosive, emits vapors and sometimes burns with a nearly invisible flame. Soapmakers working with ethanol should keep ethanol away from an open flame like a gas stove at all times. Always keep a fire extinguisher and a spray bottle filled with water handy when working with ethanol. If the ethanol should catch fire, aim the extinguishing spray at the base of the flames.