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Results of My First Essential Oil Distillation

August 29, 2017

Back in July I bought myself an Essential Oil still and immediately tried it out on a batch of Eucalyptus leaf that I’d brought back from my property. I collected up a few precious drops of essential oil – around 30 mls actually which I was quite pleased with (from around 3-4Kg of fresh leaf) and now the results are in.

Essential Oil Batch 1 Hydrosol. Eucalyptus Camaldulensis. 

Essential Oil Batch 1:  Eucalyptus Camaldulensis Aroma Chemistry and GC. 


Great but what does all that mean?

If we look at the hydrosol first we see some figures expressed as ppm (Parts Per Million).  1000 ppm is equivalent to 0.1% so 2445.47 ppm = 0.244547 % which we can round to 0.245% What that means is that my hydrosol contains just under 1/4 of a percent of oily stuff and that manifests as a beautifully aromatic smelling water.  What is interesting is that this hydrosol is pretty much crystal clear, contains no ‘solubiliser’ (We talked about these earlier this week) and no preservative.  On an ingredients listing I could label this as ‘Eucalyptus Hydrosol’ and that would be that.  I often get asked if hydrosols are OK to use as a replacement for water in an emulsion and I also get asked if hydrosols require preservatives so let’s answer those questions.

Hydrosols are the water of distillation and as such they have been heated under pressure before being condensed again.  The heating in a normal steam distil vat gets to just short of 100C so way hot enough to pasteurize the water.  The water that is used in distilling can be any type of water really so it could be from rain, from the general tap or distilled.  I am not sure if it makes a difference to what comes out the other end – that might be a subject for another day – but what I do know is that the water gets to be the soaking fluid for a heap of dirty plant matter.  Plant material is usually taken straight from the field (or possibly the ground is wild harvested) and popped into the vat.  Gloves aren’t often used and there’s no telling whether along with the leaves you’ve got a fly, worm or fungal spore or two.  So even if you use the cleanest of water to start with, by the time it has seen the plant matter it ends up looking a bit like old scummy stewed tea!

The water that comes off the still comes off as steam and is condensed through a copper tube that rapidly cools it turning the steam back to liquid.  The liquid then sits, usually in an open top container and waits for it to fill, this can take an hour or more depending on the vat size and the size of the receiving vessel but needless to say the receiving vessel is usually open to the elements.  So again, while the condensed steam may be crystal clear and clean, it might not remain like that.   I’m currently waiting on my hydrosol to age naturally for a month or two longer so I can get a series of micro results on it.  I can already notice a bit of clouding on the surface of the water from the first batch – that may or may not be a micro issue but if it is, it is clear that I’d have to clean up my act in order to sell this hydrosol as an ingredient.   So my answer to those wanting to use a hydrosol in a formula is to make sure you get the micro results first and if you want to use a hydrosol as a product, I’d be almost guaranteeing that if you want a decent shelf-life you will be needing to add a preservative.

But what about the PPM stuff?

OK so this tiny fraction of awesomeness is what makes this a ‘product’ or ‘bi-product’ and not just water.  The hydrosol smells divine, very aromatic and light and it is because of this small fraction of oily stuff that’s found its happy place stuck into the water phase.  The vast majority of my hydrosol smelly stuff is 1,8 Cineole (also known as Eucalyptol) which, according to Tisserand and Young’s ‘Essential Oil Safety’ presents a low risk of both skin irritation and sensitization.  This aroma chemical is present naturally in a wide range of essential oils and it has a fresh, classical Eucalyptus smell. Apparently it is used as a counter-irritant which I’m less familiar with but it’s major use is as an expectorants for colds and sinus issues. – the classic Vics vapour rub type thingo.

So is this an awesome skincare ingredient?

Based on the evidence above you would be right in saying that this is nothing very exciting, a bit of Eucalyptol  and a tiny fraction of other stuff in some potentially dirty water – what’s the big deal?  But I think it is all rather lovely – an aromatic bi-product from a plant distillation that can have its risks measured (micro) and if proved to be manageable can make for a nice easy way to get a pleasant bit of aroma into a product without the need for a solubiliser.  Simplicity at its best!

The Essential Oil.

The analysis for the essential oil came out almost text-book like for this type of Eucalyptus (there are many).  The only thing it was light on was the aromadendrene which should be between 0.6-1.4% (mine was 0.01%).  I am not 100% sure why I’ve got a low value here but I am guessing it might have something to do with the very high boiling point of this compared to other aroma chemicals:

Aromadendrene: 261-263 C bp 

1,8 Cineole: 176-177 C  bp

Limonene: 176 C bp

p Cymene:  177 C bp

Terpinen-4-oil  211-214 C bp

Phellandrene 171-172 C bp

The pressure that builds up in the vat does ensure these essential oil components come over into the vat at lower temperatures but I wonder if my vat is leaking a bit and is therefore at a lower internal pressure that it could be. That is certainly something I can work on.  Of course it might not be leaking that is the issue (if indeed there is one).  It might be that there is not enough stuff in the vat – too much space to fill  – or the other way, too much stuff and not enough space for steam?  I really do have to do some work on the physics of this thing I think.

The Gas Chromatography graph is what we typically associate with an essential oil although few people would really know a good one from bad.  I did study analytical chemistry up to my honours year at Uni, in fact my Uni honours project was an analytical one but that was a long, long time ago but needless to say, just having a GC machine doesn’t guarantee you a good graph. It takes a lot of prep and understanding to set these things up in a way that give meaningful readings. I’m just glad the guys at Southern Cross Uni know what they are doing!

So there you have it!  I pretty decent first stab at an essential oil and hydrosol.  I’ll be sending off some hydrosol for micro in the next month and hopefully sometime after that I can share those results with you.

Can’t wait for my next batch!


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