# Optimal temperature to mix in essential oils?



## Sapo (Feb 8, 2017)

Interested primarily in liquid soaps, but also for bar soap. I imagine the answer is similar anyway.


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## christost7 (Feb 8, 2017)

Not sure I really understand the question :
You mean the optimal temperature of the soap batter before you add the essential oils?
Or the optimal temperatures of the essential oils before you mix them together?


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## shunt2011 (Feb 8, 2017)

Are you doing HP or CP?   CP I add them to my oils before the lye mixture unless they are know to accelerate.  HP I wait until it's cooled down somewhat before pouring into my molds. However, the only HP I do is my shaving soap.


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## Susie (Feb 8, 2017)

The answers are vastly different.  

With bar soap, if it accelerates, you add them after you add the color.  If not, I add them to the oils before the lye.

In liquid soap, you add them after dilution, while the soap is warm, but not hot to the touch.


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## Sapo (Feb 8, 2017)

christost7 said:


> Not sure I really understand the question :
> You mean the optimal temperature of the soap batter before you add the essential oils?
> Or the optimal temperatures of the essential oils before you mix them together?



Temp of the soap.



> Are you doing HP or CP? CP I add them to my oils before the lye mixture unless they are know to accelerate. HP I wait until it's cooled down somewhat before pouring into my molds. However, the only HP I do is my shaving soap.



Forgot about the acceleration thing.



> The answers are vastly different.
> 
> With bar soap, if it accelerates, you add them after you add the color. If not, I add them to the oils before the lye.
> 
> In liquid soap, you add them after dilution, while the soap is warm, but not hot to the touch.



Aye, forgot about the acceleration thing. Was completely focused on an answer for LS, to be honest. The scents are probably altered (depending on the compounds/makeup of a particular EO) somewhat if added pre-saponification.


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## DeeAnna (Feb 8, 2017)

"...Was completely focused on an answer for LS, to be honest. The scents are probably altered (depending on the compounds/makeup of a particular EO) somewhat if added pre-saponification. ..."

Not to mention that the dilution ratio of paste to water also affects the amount of scent you'd want to add. Dilution can range from 0.5 parts water to 1 part paste up to maybe 4 parts water to 1 of paste. If you don't absolutely know the dilution ratio, you can't dose the paste properly with scent. 

Furthermore you will have loss of scent due to simple evaporation during saponification, if you don't get any chemical morphing of the scent from exposure to the lye. 

IMO it really makes the most sense to scent at the time of dilution.


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## Susie (Feb 8, 2017)

I have tried it both ways, and scents added at paste/gel stage just don't survive well through dilution.  Adding at the end of dilution gives you the most bang for your buck scent wise.   You may have to add some PS80 if you have a high SF, as your EO/FO may float.  I have only ever had one scent float, and that is the one I am using right now.  It is pomegranate FO from WSP.


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## Sapo (Feb 8, 2017)

I have just finished a minor experiment:

Added lavender EO to two 200ml soap samples at a rate of 1% (2ml):
-One at 45˙ Celcius soap temp.
-One at room temp. soap

Result: exactly the same.


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## Steve85569 (Feb 8, 2017)

Sapo said:


> I have just finished a minor experiment:
> 
> Added lavender EO to two 200ml soap samples at a rate of 1% (2ml):
> -One at 45˙ Celcius soap temp.
> ...



That works for that EO.
If the EO has a flash point of 45 degrees Celcius the results would be very different. The answer is that each and every EO will react differently because, well, they are different.

I would check on the flash point of a particular scent just so I could "help" it stick.
After all the scents we use are almost always the most expensive ingredient.


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## DeeAnna (Feb 8, 2017)

Flash point is the temperature at which a combustible or flammable substance will burn if exposed to a flame (not a spark -- it has to be a flame). The material will burn as long as it is at or above its flash point temperature AND a flame is present, but the fire may stop if the flame is removed.

The flash point needs to be considered when looking at shipping and storing combustible and flammable substances, because a low flash-point material in a fire can make the fire much worse. That is why there are often hazardous material charges or restrictions on shipping low flash point materials.

Many people use the flash point as the temperature at or below which they can "safely" add fragrance to soap. I don't pay any attention to that -- the flash point temp in this context is pretty much meaningless. When mixed into the soap, the fragrance won't burn for one thing. For another, one shouldn't be mixing fragrance into soap batter close to open flame. And finally, any fragrance -- even if it is below its flash point or doesn't even have a flash point -- is still going to evaporate. The warmer the soap, the faster the evaporation.

My goal, whatever the fragrance, is to add it at the coolest temperature I can manage. And keep in mind evaporation isn't all bad -- if a fragrance didn't evaporate into the air, you couldn't smell it!


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## Sapo (Feb 8, 2017)

Steve85569 said:


> That works for that EO.
> If the EO has a flash point of 45 degrees Celcius the results would be very different. The answer is that each and every EO will react differently because, well, they are different.
> 
> I would check on the flash point of a particular scent just so I could "help" it stick.
> After all the scents we use are almost always the most expensive ingredient.



Similar note: Dunn briefly talked about boiling points in this article: http://roberttisserand.com/2011/06/essential-oils-in-soap-interview-with-kevin-dunn/

But I find the notion of avoiding a 204C/399F soap (for lavender, for example) a bit on the funny side. We never really exceed 95C/203F .


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## Steve85569 (Feb 9, 2017)

Sapo said:


> Similar note: Dunn briefly talked about boiling points in this article: http://roberttisserand.com/2011/06/essential-oils-in-soap-interview-with-kevin-dunn/
> 
> But I find the notion of avoiding a 204C/399F soap (for lavender, for example) a bit on the funny side. We never really exceed 95C/203F .


Granted. 

If you check I think you will find some EO's and I have some FO's that have a much, much lower evaporation point.:think:


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## Susie (Feb 9, 2017)

Sapo said:


> I have just finished a minor experiment:
> 
> Added lavender EO to two 200ml soap samples at a rate of 1% (2ml):
> -One at 45˙ Celcius soap temp.
> ...



So, you assume that that result will carry through long term with no testing?  I suggest you continue to test those against one another over the next year before deciding that that result is "exactly the same".  

I have not used that EO in liquid soap, as I do not care for lavender.


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## DeeAnna (Feb 9, 2017)

The boiling point doesn't really apply to this question any better than flash point because, as Sapo noted, we're not dealing with temps anywhere near the boiling point. That said, the boiling point of an EO might actually relate better to its volatility than the flash point. The connection I'm suggesting is EOs with low BP => more volatile.

What would be even better is to know the vapor pressures of EOs in the temp range at which we normally work. Hard numbers on vapor pressure are not readily available, unfortunately, but there is a body of empirical info that relates to vapor pressure -- the classification of EOs into top, middle, and bottom notes. Top notes (examples -- citrus, some florals) are the most volatile and shortest lived and bottom notes (typically seed, resin, wood EOs) are least volatile and longest lived.


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## Sapo (Feb 9, 2017)

Strictly for liquid soap...

How does any of this *actually* relate to "what is the ideal soap temperature/method for adding EO", though?

Do we have any evidence that EO mixed into soap at a certain temp. produces a good outcome, but if it gets mixed into it at room temp soap, the outcome is bad (separation or whatever the claimed side effect is)?

So far the only connection I see is: the hotter the soap -> the closer you'll be to the BP -> the more of it will evaporate during the hot period.


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## Susie (Feb 9, 2017)

You are welcome to take years of testing for yourself to answer your own question since you find our answers lacking.


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## Sapo (Feb 9, 2017)

They are indeed lacking, but not because I don't want to listen or believe you, but because you simply *don't provide an explanation* on what the problem is.

Person A: red socks ain't good.
Person B: Why?
Person A: trust me, years of experience.
Person B: ...

I'm more than willing to learn (its why im here, I find it fruitless to reinvent the wheel when someone more experienced can steer me away from senseless trial and error), but hey, "just cuz" isn't an answer. Do tell what the outcome of improper EO mixing was (and what improper EO mixing is).


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## mx5inpenn (Feb 9, 2017)

Sapo said:


> They are indeed lacking, but not because I don't want to listen or believe you, but because you simply *don't provide an explanation* on what the problem is.
> 
> Person A: red socks ain't good.
> Person B: Why?
> ...



Sapo, I understand you want to learn.  That's great! But maybe a little less abrasiveness would be better? Catch more flies with honey and all that...

I don't make liquid soap, but there are several people on this forum that have made large quantities and tried many methods. There isn't always a known reason why something works the way it does, but through lots of tests and trial and error, you still find that's how it works best. A simple "do you know why this is the result?" would be better received. If the answer is nothing more than I've tried it these 4 ways over 10 batches and got wxyz results, its still using the appropriate testing methods. Its still a valid response and helpful answer to your question.


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## DeeAnna (Feb 9, 2017)

"... So far the only connection I see is: the hotter the soap -> the closer you'll be to the BP -> the more of it will evaporate during the hot period. ..."

That pretty much sums it up. This is pretty much the perspective most people use when talking about adding fragrance to soap. I suspect you're on your own to develop a more rigorous model.

You're wanting to scale up from what I gather from your other threads, so what hobby soapers observe with our small batch sizes and small scale equipment won't necessarily apply to a larger scale operation anyway.


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