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‘Why is olive oil soap so hard to make?’ Well the answer may be in its unsaponifiables…..

May 29, 2017

Last week I had a chat to a rather lovely person who was struggling with their Olive Oil soap. Now I’m not a great soaper myself – no patience, can’t be bothered with making them look fancy etc – but I am a chemist and as it turns out, that is pretty blooming handy!

So after explaining to me what she was trying to do and how her recipe was currently constructed I put to her a theory, a theory about unsaponifiables and it has led to this.

Let me take you on a journey.

Vegetable oils are not created equally with regards to chemistry. In fact you couldn’t get a more diverse set of ingredients (that we all tend to take for granted).  I’ve spoken before about how some vegetable oils have the power to enhance skin penetration and how others can contribute positively to a products inherent sun protection (although not by having an SPF as such) but now it seems there is something else to think about.

When you are soaping you need to rip the oil apart and chemically change it.  The triglycerides that make up the bulk of the oil have to part ways with their glycerin (Tri = three, glycerol = glycerin.  Three fatty chains on a glycerin backbone).  Those fatty chains then use the hand that they were holding onto glycerin with to become a soap – a soap is literally a fatty acid plus an ionic head group – Sodium and Potassium (from the lye) are the most common but Triethanolamine soaps are also well-known.   This reaction is known as SAPONIFICATION and it is one of the most important (if not THE most important) reaction in cosmetic chemistry as it gives rise to many of our functional ingredients.

But the saponification reaction doesn’t work on EVERYTHING contained within that vegetable oil.

Vegetable oils will almost always contain a proportion of ‘stuff’ that won’t saponify.  Jojoba oil is particularly resistant to saponification and will only form soaps in very harsh conditions – much harsher than your typical hand-made soaper can manage.  That is one reason why Jojoba doesn’t make a good soaping oil on its own – it simply doesn’t turn into soap.  But it can make a very good super-fat / moisturising bar if that’s more your thing.

This ‘stuff’ that doesn’t want to play with the lye and become soap is called the ‘unsaponifiables’ and each oil has its own unsaponifiable footprint.

My theory with the Olive soap was that the unsaponifiable portion of the oil is quite high and that if that isn’t factored into the ‘super fat’ calculation there is a danger of not using enough lye to get a good bar.

To my surprise, when I looked at a range of vegetable oils, the unsaponifiable percentage of Olive Oil wasn’t the highest.  It turns out that oils such as Rice Bran, Walnut and Wheatgerm have much higher unsaponifiable fractions.   So the idea that the unsaponifiable fraction percentage would be all I needed to predict soaping behaviour wasn’t all of the story.  It was then that I decided to look into the composition of this fraction for each oil. I was particularly interested in the role that the Olive Oils Squalene might play in making Olive Soap difficult to make.  As it turns out I think I was on the right tracks. However, looking into the chemical composition of the unsaponifiable fraction wasn’t that easy mainly because of the different methods and units of measure used in each study but also because of the natural diversity of ‘grown’ products.  To put it simply, there were large variations between the numbers that I found so I basically had to do a lot of reading to get a rough (very rough in some cases) idea of what’s what. I gave up writing all the references as I got bored (and this is only a blog after all)…..


The chemistry of the unsaponifiable fraction is interesting. It is here that we get the antioxidants,  some anti-inflammatories and some anti-microbial activity of oils as well as some of the UV protective qualities.  Indeed some oils are harvested for this unsaponifiable fraction which is separated off and sold separately to the main oil as more money can be made that way.   I’m sure we are all aware that we can purchase Olive Squalene as a separate ingredient and that natural vitamin E is extracted from vegetable oils and sold separately either as mixed tocopherols or as alpha tocopherol (the biologically active component).   The financial value of this unsaponifiable fraction has meant that it has been widely studied for some oils and that has been very useful for me in this work but like I said, please do take the numbers as indicative as it has been hard to nail down meaningful figures or ranges given the natural variation between samples.

So there is an unsaponifiable fraction and this fraction contains a mixture of different chemicals or ‘stuff’.


unsaponifiable table

There is no doubt when looking over the data that I’ve managed to compile that the unsaponifiable fraction of Olive Oil is quite different to the other oils in its squalene concentration – it has heaps more.   I’ve been wondering if there is something particular about squalene in the soaping environment that makes olive oil soap quite difficult to make and long to cure (it is said that pure olive oil soap can take 12 months to fully cure)?

Chemically Squalene is a hydrocarbon which means it is composed of hydrogen and carbon only (quite simple really).  It has a straight-chain structure with some double bonds and is chemically non-polar and hydrophobic (water hating).   Both of these features mean that when it comes into contact with soap, the soap will try to emulsify it.

If we think about using a bar of soap to wash grease from our hands we know that the soap interacts with the oil, lifting it from the surface of our skin and into the rinse water thus leaving our hands clean.  In a bar of soap the squalene (grease equivalent) doesn’t so much wash away as become emulsified thus changing the very structure of the bar.

I imagine that a bar of soap with none of these straight chain hydrocarbons will be a relatively densely packed lump of saponified oil (soap) just waiting to clean a surface. However, add a proportion of these hydrocarbons INTO the structure and it is likely you will end up with an internal phase in the soap – a sort of emulsion. The soap part becomes the emulsifier and the hydrocarbon the internal phase (emulsified substance).

I know from my work with emulsified lip and body balms that adding an emulsifier and internal phase to a balm changes the structure of the whole product, sometimes making it softer and sometimes gritty (if the phases aren’t particularly well mixed).  This all makes sense when you think about it as a two-phase soap could very well end up less densely packed than a single phase, homogenous ‘soap’ and this might be the start of the trouble.  Also, let’s not forget that if some of the ‘soap’ part of the bar is actually being put to work as an emulsifier it will be less available to be soapy so I’d expect a reduction (or change) in lather behaviour and cleansing ability too.   Things that do play out when you talk to soapers.

So what about the other unsaponifiables?

If you look at the table I put together you see that the other unsaponifiables have structures that are more similar to each other, give or take a few carbons.  They contain aromatic ring structures and oxygens so are no longer hydrocarbons.   From my reading I know that the tocopherols (vitamin E isomers) don’t become saponified during soaping and I also know that their presence in soap doesn’t seem to affect the soap behaviour too much (as far as one can see).  I think it is very likely that the tocopherols just sit dispersed throughout the soap doing their own thing and helping to prevent premature oxidation (rancidity) where possible.  The same could also be said for the phenols and sterols.  This is possibly why some oils (such as Rice Bran) can have a much larger unsaponifiable portion than Olive Oil but still be easier to soap with – quite literally the unsaponifiable portion just sits in the mix rather than it interfering with it.  That said, I would still be inclined to count this unsaponifiable percentage into my soaping calculations so as not to end up with a super-fat that is much larger than I was anticipating.

Hang on, what is super fat?

Super fat is the amount of unsaponified fat left over after soaping. Soapers usually leave some oil un-saponified to make the soap more moisturising/ nourishing.  While super fatting your soap recipe can be a good thing, going too far can lead to disaster.  A soap with too much super fat may be very soft and very un-bubbly as described here by the Soap Queen. 

What we know about super fat does seem to add up and make sense when viewed against this natural unsaponifiable issue we are talking about here.  Make sure you take it into account for your soap blend would be my advice.

So back to Squalene, can this theory that squalene concentration makes for a tricky soap be tested?

Well yes and this is where I would like YOUR help (because I’m not a great soaper anyway).  I reckon that you could take an oil, any oil and experiment with soaping with it with different squalene concentrations by buying some squalene and simply adding it.

I would start off with a simple, predictable soap blend such as coconut and palm – this by the way is a simple and predictable starter soap blend BECAUSE palm and coconut are very simple and predictable oils with very low levels of unsaponifiables.  It would be good to start by incorporating 1 or 2% Squalene into the mix, then 4 and finally 6% to see how that goes.  If the soap becomes softer, less bubbly or takes longer to cure then we can safely say the squalene is implicated.   Worth giving it a go I think!

But before we get all excited it is worth remembering that oils are naturally variable.

One thing I did notice in compiling this data is how very hard it is to get comparable data (I mentioned this above).  The oil content and composition in vegetable seeds can vary hugely depending on their variety, growing conditions, age, time and conditions of picking and processing method.   Keep this in mind when comparing your soaping results with others or from batch to batch and especially when moving from one oil supplier or type to another.  It is likely that cheaper vegetable oils contain lower amounts of unsaponifiables as they may have been stripped out to sell separately.  If in doubt do ask for a specification that includes the fatty acid composition and the unsaponifiable fraction.  It might help to keep you on the right track.

And lastly,  remember to only change one thing at a time.

If you do plan to turn into an investigative scientist do yourself a favour and only change one component of your experiment at a time.  Set yourself up so you can use the very same batch of oil across the whole experiment and try keeping mixing equipment and temperatures even.  That way, and with your help we might just completely nail this thing and make soapy disasters a thing of the past.

One last thing.

Before I go and in case someone says ‘yes but you didn’t do ‘xxxx’ oil, how does that react?’  Let me tell you that the reading to get this information did my head in.  It took four days and nearly 100 papers to get what I’ve got for this (free) blog post and even then I don’t feel entirely happy with all of the data although it serves its purpose.  I am a chemist who has worked in this area for 19 years now and has maintained an interest and passion for this type of research and application work.  That doesn’t mean that I presume I’ve got it all right but it does mean that my theory has some measurable logic behind it and my data has some degree of error checking built-in.  Enjoy and please do feel free to help build on this. It is exciting.

Happy experimenting.

Oh and here’s another interesting Soap Queen post that helps you visualise pure single-oil soaps. 

Amanda x



One Comment leave one →
  1. Rachel Malek permalink
    June 4, 2020 2:38 am

    Have officially fallen in love with your blog. I came back to Italy after a brief stay with my hippy roots in Canada, and was converted back to the good old hippy-hygiene ways: Dr. Bromners Castile Soap. However, the bottle I brought back here is already almost finished, and it is honestly just too expensive to justify for the amount we use at home. (Yes, also as shampoo, followed by diluted red wine vinegar which my husband makes with local wine and the mother given to him by, well, his mother. I usually use it one to two times a week, and use the vinegar rinses every other day in the shower and arrowroot powder when needed as a dry shampoo between washes).

    Tangent about my hippy hair care aside, I have nervously decided to try making our own Castile soap. I am hoping to use our own olive oil, as we usually produce more from the trees in the garden than we can use before the next harvest and end up giving it away. This is the pure, green, unfiltered unaltered and unpreserved stuff you can really only find in small batches here in Tuscany.

    Basic idea, this oil is essentially free for us and we have it in excess, so why don’t I make my hippy soap out of that and save us some money?

    Your article has made me curious to understand more about how the composition of the olive oil will affect the soap-making process and final results. There is a notable difference in scent, colour, consistency and taste between this oil and what you buy in the store (even when I shelled out for fancy stuff in Canada).

    I’m wondering if this is because of an increased amount of unsaponifiables (or squalene? If I understood your post correctly they are referring to the same thing, which is taken out of commercially refined olive oil but would be left in this oil I assume.)

    Also assuming that if it is already hard to make soap with 100% olive oil, it would be even more difficult with this. Nonetheless, I also assume that our backyard oil is more similar to what was used in the early/traditional ways of making castile soap. My hope is that this will have some positive added effect in the final product, although I have no clue of the science of what those added effects would be.

    Anyway, from this non-scientist ‘cook’ thank you for the interesting article! I will definitely feel more confident and moderately more aware of what the heck is happening as I embark on my first attempts at ‘soaping’. You rock.

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