Classic Bells > Soapy stuff > Sodium lactate

Sodium lactate in soap

What does it do in soap?

Sodium lactate (SL) is used as a humectant and moisturizer in cosmetic products. In soap, sodium lactate makes hot process soap more pourable and smooth, adds hardness to bar soap, and makes it easier to dilute liquid soap.


What kind to use?

Sodium lactate is sold in pure powder form and as a liquid solution containing 60% sodium lactate. The liquid is more convenient to weigh and use for soap and cosmetics, since only small amounts of SL are needed.

The powder is hygroscopic (absorbs water from the air) so it requires careful storage and handling. The powder can also be irritating if inhaled.

Sodium lactate is also formed when you add a source of lactic acid to your recipe. Lactic acid is found in fermented dairy products such as yogurt, buttermilk, and kefir.


How to make your own sodium lactate masterbatch?

Sodium lactate powder is dusty and you only need tiny amounts, so I recommend making a 50% or 60% masterbatch SL solution and using this liquid when making soap rather than the powder.

For a 60% masterbatch that is comparable to the commercial SL liquid, mix 6 parts sodium lactate powder with 4 parts distilled water by weight.

To make a 50% masterbatch, mix 1 part SL powder with 1 part distilled water by weight.

Stir until the powder is dissolved. Store the solution in a tightly closed container at room temperature.


How much should I use?

Bar (NaOH) soap: Typical dosage is 20 g to 30 g of 60% sodium lactate solution per 1000 g of fats (2% to 3% of total fat weight). Dosage range is 10 to 30 g of SL solution per 1000 g of fats (1% to 3% based on total fat weight). Over 3% can make bar soap softer and more rubbery, so more is NOT always better.

Some soapers adjust the amount of SL depending on the fats. They use more SL for a bar soap recipe high in liquid fats and less for a bar soap recipe high in solid fats.

Liquid (KOH) soap: Typical dosage is 30 g of 60% sodium lactate solution per 1000 g of diluted soap weight (3% of diluted soap weight). Diluted soap weight is the sum of the soap paste weight + dilution water weight.


How much lye does it neutralize?

None! Do not adjust your lye weight when using sodium lactate.


How should I add it to my soap?

Bar (NaOH) soap: If using SL solution, blend it into your fats, add the lye solution, and soap as usual. If using SL powder, dissolve the sodium lactate in about 2 times its weight of water. Stick blend that mixture into your oils.

Liquid (KOH) soap: Stir the SL powder or solution into the dilution water.