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I am using alcohol as an emulsifier. Of course, I can use a lot of alcohol to mix the oil and water but I do not like the color and the % of alcohol in the mix. The best mix I made was 10ml water, 0.5ml (10 drops) essential oil, 5ml alcohol because the mix looks super milky and when left alone the oil does no lt deposit. I repeated this formula again but the result is different (maybe the temperature was different, or the stirring, etc). My question is: what is the best way to stir the essential oil with the alcohol? Should I heat it? Should I stir it with an instrument other than just stirring in a beaker? All emulsifying tips are welcome!

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  • $\begingroup$ It is not really clear what you would like to reach. Do you want to make a stable emulsion? I cannot compute what does "I don't like the % of alcohol in the mix" or color (isn't it white??) mean. Also, why do you use alcohol as emulsifier? $\endgroup$
    – Greg
    Commented Aug 17, 2016 at 5:10
  • $\begingroup$ First of all, alcohol is not an emulisfier but a cosolvent. Please specify whether you want to obtain a homogenous solution, emulsion or dispersion. These are three different goals and require three different approaches. $\endgroup$
    – vapid
    Commented Aug 17, 2016 at 9:37
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    $\begingroup$ I want to make a stable emulsion. If I put too much alcohol the mix turns yellow. If I put too little alcohol the oil does not mix with the water. If I put too much alcohol the mix becomes flamable. The perfect mix should turn it into a milky white, but I cannot accomplish it constantly. I use alcohol because it is cheap and easy to get anywhere. $\endgroup$
    – Giancarlo
    Commented Aug 17, 2016 at 18:20
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    $\begingroup$ I am not sure if what I need is defined as a solution or emulsion; I want to spray essential oils diluted in water, but need the best result to make the water and oil mix without having to shake the bottle every time. – Giancarlo 1 hour ago delete $\endgroup$
    – Giancarlo
    Commented Aug 17, 2016 at 19:42
  • $\begingroup$ Any tips or recommendations? $\endgroup$
    – Giancarlo
    Commented Aug 18, 2016 at 16:13

4 Answers 4

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A solution would be the best for spraying, and it would require dissolving the essential oil in an appropriate organic solvent. However, if you are concerned about the flammability, then a dispersion in water would be your best option. Basically, all you need is a stabilizing agent and a proper procedure. I am sure that you will find all the necessary information on this site. It has all the basics about emulsions, it lists various emulsifiers (stabilizing agents) and procedures. For your purpose, I think the best option would be the Bottle Method.

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  • $\begingroup$ Those two html pages are not available. Can you provide the information here? $\endgroup$
    – user12711
    Commented Oct 18, 2023 at 20:11
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To make an emulsion, a stable milky mixture of oil and water, you need an emulsifier. Alcohol is not an emulsifier, so the mixture will separate at some point. The most common emulsifiers used in cosmetics can be found here.

If you are making this at home and do not have access to these kind of products, you can try with organic soap. This is normally oil hydrolyzed with caustic soda (NaOH) and is in essence what is listed as neutralized fatty acid soap.

Normal stirring is also many times not enough and a high shear mixer is generally used. So mix it as hard as you can.

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  • $\begingroup$ The link you shared is not available. Can you share the information here? $\endgroup$
    – user12711
    Commented Oct 18, 2023 at 20:19
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By alcohol, I assume you mean ethanol. A better choice might be isopropanol (rubbing alcohol). If either ethanol or isopropanol can be mixed with your essential oil in a 10:1 ratio to give a clear solution, then the alcohol is a solvent. The water is not a solvent for the essential oil, but the alcohol might be able to dissolve some water without expelling the oil.

I suggest you make a triaxial graph to plot the concentration ratios of ingredients that are clear (solution) or milky (stable (?) emulsion) or quickly separating (unstable emulsion). The advantage of a triaxial graph is that you can find a location on the equilateral triangle for any combination of three ingredients - and do some interpolations to find where you can be. This is a picture of a triaxial graph:

enter image description here

It might be possible to use another solvent, e.g., acetone, in whole or in part. One way to stabilize an emulsion is with surfactants; high shear is best for reducing the size of the micelles. Another way to stabilize an emulsion is to use a thickener that prevents the oil micelles from settling or creaming.

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  • $\begingroup$ I'm trying to make a 1 to 2% solution of cedarwood oil with water/alcohol (rubbing) to spray for fleas inside a living space. My plan is to mix my 1 ounce bottle of pure essential oil with 10 ounces of isopropyl. That should look milky white. Then I'm going mix that with 5 to 10 parts water to make the ultimate solution stable enough to shake once and spray for several minutes (1 to 2% cedarwood oil). Should that work? $\endgroup$
    – user12711
    Commented Oct 18, 2023 at 20:17
  • $\begingroup$ actually more 70% isopropyl will need to be mixed than 10 to 1 ratio because it's only 70% ?? $\endgroup$
    – user12711
    Commented Oct 18, 2023 at 20:28
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    $\begingroup$ @user12711: The 10 to 1 ratio is to determine whether the oil is soluble in pure alcohol (i.e., isopropanol). If so, maybe water can be added. But some oils are not soluble even in pure isopropanol, so the mixture will be cloudy and will probably separate. In this case, adding water will not help. The OP made one successful mixture, but could not replicate. Using a triaxial graph can map what compositions are useful. It may show how some compositions are milky, some settle, some are clear, depending on composition. Procedure (heating, stirring) needs other experiments. $\endgroup$ Commented Oct 19, 2023 at 3:08
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You can use ultrasonication and no solvent (water + oil + sonicating = emulsion). The sonicator degasses the water which allows the oil to disperse homogeneously throughout the water.

I hope you can access a sonicator if not there are freezing techniques which also degas water.

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