What is an Emulsion?

Every trade, every craft, every art has its own little vocabulary; its set of terms that it uses as shorthand, or for precision – but these aren’t always clear to the outside observer. It can often feel that people are being intentionally obscure in their terminology. I promise that’s not the case around here! I’m going to try to define most of my terms; maybe not before I use them, but I’ll at least try to catch up afterward.

My first definition-post is a term which won’t be obscure to at least some of my readers – after all, the concept of an emulsion is familiar to both chemists and cooks. In its simplest terms it is simply two “unmixable” things – like oil and water – blended together. More technically, a stable emulsion requires an emulsifying agent – a particle which is soluble in fats at one end, and in water at the other end. This forms a skin around little tiny “bubbles” of oil in the water, or of water in the oil (depending on the relative proportions), which are then suspended readily in the other phase.

This sort of emulsion is what I’m making when I make our Hand & Body Cream; we use an emulsifying wax to stabilize it so the oils and the water don’t come apart and turn the creamy lotion into a pile of watery clumps. (eww!) It is also the form of emulsion found in mayonnaise, in which egg yolk serves as the emulsifying agent. It is possible to “break” an emulsion of this kind by subjecting it to very extreme temperatures or some forms of mechanical stress, analogous to over-beating whipped cream.

Emulsions without emulsifying agents are unstable, and if left on their own will separate into two distinct layers. A good example of this in the kitchen is a vinaigrette dressing, which must be shaken to re-mix the emulsion before each use. The emulsion phase when making soap, shortly after adding the lye solution to the oils, is like this. It would be an unstable emulsion under ordinary circumstances, but as the lye and oil are busy turning into soap in the mixture (and we keep stirring until this process is well underway), it never gets a chance to separate.

Soap Emulsion

Soap late in the emulsion phase, almost to a light trace.

And that’s that. Next up in this series: Trace.

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About Amy Young

Founder of Foam on the Range soaps. View all posts by Amy Young

3 responses to “What is an Emulsion?

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