Cold Process Soaps, Essential Oils and Trace Time
If you’ve never made cold process soap you might not be aware of the wonders that can happen when you get to the point of adding the fragrance so here’s a quick bit of background info before I start to talk about trace speeds!
Cold Process – The manufacturing method for making soap from vegetable oils and lye (usually sodium or potassium hydroxide) without heating. That said the reaction between the lye and water is exothermic (generates heat) which means that your cold soap process is actually more likely to take place at around 40-50C than room temperature or colder!
Trace – this is the point when the soap starts to take (chemically saponification is happening, the oils are changing from oil to soap). Visually the mixture starts to look like it is turning into a thickened custard – this custard is the soap!
Essential oils – OK so I’m sure you know this already but essential oils are the aromatic oils from botanical material. They are often used to fragrance the bar of soap and to give the soap some added skin care benefits.
Fragrant Oils – These are classified as synthetic fragrances or perfumes and are man-made and controlled rather than designed by nature!
OK so the point of my post was to explain a little more about trace and essential oils VS fragrance as this week I’ve had a question about that.
The saponification of oils can take a little while, we tend to add our fragrance just as trace is starting to happen as that is our visual clue that the lye is ‘seeing’ the oils and working on them – no point adding fragrance straight into the oils BEFORE this point as the fragrance or essential oils might get saponified too!
Trace is an important step in soap making and ideally you want this to happen smoothly as you mix rather than in the blink of an eye (and nobody wants it to take forever as that means you will be hanging around mixing for ages).
Fragrant oils are easy to work with because they are man-made to a specification and usually vary little from batch to batch so after an initial bit of experimenting you can work out how the oil affects trace (does it make it speed up, slow down or no change) and be prepared. Essential oils are a bit more complex!
Because essential oils are natural they vary from season to season, location to location and batch to batch. This can make working with essential oil based aromas very tricky for the soap maker as trace times can literally go from one extreme to the other making the saponification time hard to plan for. For this reason we would always recommend running a trial batch to assess trace time whenever you get a new batch (or change supply) of essential oils. Some people worry that a dramatic change in trace time means that their essential oil is bad or wrong but it is often more likely that the oil chemistry is just naturally different and there is nothing necessarily wrong with that.
If you are fascinated by the soap process and want to know more I recommend going through the Soap Queen archives on You Tube as there are some excellent tutorials on there and you can see what I am talking about!
Soap manufacture is probably the most ‘chemical’ of processes us cosmetic chemists do which is ironic given that many people see it as more of an art than a science but I’m OK with that.
Have fun and remember to test out your essential oils before committing to a huge soapy batch.