Preservatives keep our products safe from microbial invaders like bacteria, mold, yeast, and fungus. When we make anything that contains water or may be exposed to water, we must include a broad spectrum preservative – one that prevents all manner of ick - lest we face the heartbreak of a fungus or bacteria lled product that’s not only gross, but dangerous.
When choosing a preservative, keep in mind the pH range of the product. Using Vitamin C, salicyclic acid, and alpha hydroxy acids will create more acidic products with pH levels around 3, while some surfactants, like decyl glucoside or sodium coco sulfate, or emulsifying systems like stearic acid-TEA, are alkaline with pH levels over 8 and often higher than 10.
Consider the type of product you’re making - some preservatives require oils to work well, some prefer more watery environments – and the ingredients, especially harder-to-preserve ingredients like botanicals, clays, or extracts. Also consider your packaging. Products in jars are much, much harder to preserve than those stored in bottles with disc caps or airless pumps.
Vitamin E, citric acid, grapefruit seed extract, or rosemary oleo extract are anti-oxidants, which help retard rancidity of oils and butters. They do nothing to prevent contamination.