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What are the main reasons for emulsion instability?
Hi, all.
I have created a couple of oil-in-water products recently that looked perfectly fine on Day 1 and Day 2, and then starting about a week later (stored at around 75 degrees Fahrenheit) began to show minor signs of separation/unevenness.- What is typically the first place you look when addressing this kind of issue? Is it insufficient (%-wise) emulsifier?
- Also, does ethanol (added during cool down) lessen stability?
Thank you.
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18 Replies
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The main reason why an emulsion is not stable is that you messed it up… :blush:Seriously, read a book about emulsions and what factors impart or hamper stability. I suppose it would be mere speculation to guess which of all the possible factors happen more often in cosmetic inventing than others.1: The first place I look when addressing this kind of issue is my kitchen. That’s where I make most of my trial products. There I look at the product and observe, maybe wait longer or spin it in my centrifuge. The appearance of the semi-separated emulsion can tell you a lot. If I had some money left (or next time I want to buy something new), I’d invest in an optical microscope which would help a fair bit. If you have access to a LumiSizer or a Zetasizer, now, that would be something! Given that you ask the question you asked tells me, that you have no idea what these machines do… which means, read a book about emulsion basics.2: Depends. Ethanol can have a positive, negative, or no effect on stability.
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@Pharma, I don’t have access to a proper lab and I invested in a decent quality optical microscope some time after I moved to w/o. I totally agree that it helps a lot as I want to know righ away whether emulsion will separate in two months or not.
Having said that, it’s hard to mess up o/w. So if o/w separates - back to reading.
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suswang8 said:Hi, all.
I have created a couple of oil-in-water products recently that looked perfectly fine on Day 1 and Day 2, and then starting about a week later (stored at around 75 degrees Fahrenheit) began to show minor signs of separation/unevenness.- What is typically the first place you look when addressing this kind of issue? Is it insufficient (%-wise) emulsifier?
- Also, does ethanol (added during cool down) lessen stability?
Thank you.
We can not begin to ‘guess’ what your issues are. If you are looking for answers we need to know the details. Formula with percentages, process etc.
The issues could be down many different avenues, from not using a primary emulsifier, to not using enough emulsifier, to having antagonist in the formula, so not following emulsifiers specific directions….(temp etc).
If you are looking for answers, post your formula, pH, and technique/process. We have actually seen people try and make emulsions with a whisk.
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ngarayeva001 said:@Pharma, I don’t have access to a proper lab and I invested in a decent quality optical microscope some time after I moved to w/o. I totally agree that it helps a lot as I want to know righ away whether emulsion will separate in two months or not.
Having said that, it’s hard to mess up o/w. So if o/w separates - back to reading.
Hi do you mind sharing the model of the optical microscope and the price range? Love to see how this works. Thanks
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Homogenizer here, so at least I have that part covered
, although maybe it’s not doing the greatest job. And the product does seem to be fully “homogenized” for about 24h after blending, if that matters. 8.00% Sweet Almond Oil 3.00% Tetrahexyldecyl Ascorbate 0.80% Lecithin 0.80% Behenyl Alcohol 3.00% Ethanol 1.00% Bakuchiol 76.10% Water 3.00% niacinamide 1.00% Green Tea Extract 2.00% Glycerin 1.00% Spectrastat 0.30% xanthan gum (I forgot to add my sodium phytate, but I don’t think that would have effected short-term stability like this.)
I dissolved the GTE and niacinamide into water, then added my xanthan/glycerin slurry. Put that on the burner. I separately heated the almond oil, lecithin, behenyl alc, vitamin c, and bakuchiol potion. I then added the water phase into the oil phase purty slowly, mixing by hand. Then homogenized for a couple of minutes. Then added ethanol and Spectrastat.
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Lecithin alone is not quite stable in long term, and you sure 0.8 is enough?
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Pattsi said:Lecithin alone is not quite stable in long term, and you sure 0.8 is enough?
Bingo!
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+ behenyl alcohol 0.8%, which I believe is considered a co-emulsifier.
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@TheSocksTooBig I have this one Swift SW350B Siedentopf Binocular Compound Microscope for Adults,40X-2500X,Wide-field 10X and 25X Eyepieces, LED Illumination, Abbe Condenser, Double-Layer Mechanical Stage https://www.amazon.co.uk/dp/B07LGYR99H/ref=cm_sw_r_cp_api_i_8W9YDC1KZMZWRKH1QD8H?_encoding=UTF8&psc=1
But, you can see emulsion droplets and pigment distribution with 25x eyepiece plus 40x magnification (even 10x eyepiece work). My point is the 100x lense that’s used with oil isn’t needed. The models without oil lense are cheaper.
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Re formula, I am with @Pattsi and @Graillotion, the emulsification system isn’t adequate. Get a proper emulsifier. I always suggest Arlacel 165 (ala lotionpro 165, aka Glyceryl Steatate+ PEG-100 stearate) but there are other options such as Ceteareth 20 plus Glyceryl Stearate. Even one of those diy ‘ewaxes’ (poly 60/cetearyl alcohol mix) would work bettee than lecethin and behenyl alcohol. I prefer ethoxylated but you can create a stable emulsion even with ‘green/natural’ emulsifiers, just make sure you pair them and use stabilisers (which you already do)
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ngarayeva001 said:@TheSocksTooBig I have this one Swift SW350B Siedentopf Binocular Compound Microscope for Adults,40X-2500X,Wide-field 10X and 25X Eyepieces, LED Illumination, Abbe Condenser, Double-Layer Mechanical Stage https://www.amazon.co.uk/dp/B07LGYR99H/ref=cm_sw_r_cp_api_i_8W9YDC1KZMZWRKH1QD8H?_encoding=UTF8&psc=1
But, you can see emulsion droplets and pigment distribution with 25x eyepiece plus 40x magnification (even 10x eyepiece work). My point is the 100x lense that’s used with oil isn’t needed. The models without oil lense are cheaper.
Thanks a lot! Just ordered it. Something to plan around with
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@ngarayeva001
@Pattsi
@GraillotionFor what it’s worth, the manufacturer claims that its lecithin (as sole emulsifier) can handle up to 10x its weight in oil (e.g., 0.8% should be enough for 8% oil). https://www.cargill.com/personal-care/applications/skin-care-face
Regardless, I do have sorbitan stearate on hand. How does glyceryl stearate compare? I need something that is really non-comedogenic.
Thank you.
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suswang8 said:@ngarayeva001
@Pattsi
@GraillotionFor what it’s worth, the manufacturer claims that its lecithin (as sole emulsifier) can handle up to 10x its weight in oil (e.g., 0.8% should be enough for 8% oil). https://www.cargill.com/personal-care/applications/skin-care-face
Regardless, I do have sorbitan stearate on hand. How does glyceryl stearate compare? I need something that is really non-comedogenic.
Thank you.
First of all…if you believe all the propaganda that the mfg’s put out….there is probably no hope. Secondly…when you calculate…you base the calculation on everything in the oil phase…not just the oil.
Lecithin might make a good salad dressing, but will it provide an elegant product? Even if it could hold it together, imagine the feel.
There are plenty of plant based emulsifiers that have a 0 rating for comedogenic, and actually work.Just a hint….essentially everyone in the industry uses co-emulsifiers with emulsifiers that are monumentally better than lecithin…. go figure. When a mfg states their emulsifier is ‘stand alone’….move on! (Start reading books again.)
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I agree with @Graillotion on that you can’t just rely on suppliers’ claims. Lecithin isn’t an adequate emulsifier and is challenging to preserve. Glyceryl Stearate alone isn’t an emulsifier unless it’s the SE version.
Speaking of comedogenicity, it’s not as straightforward as a rating of single ingredient. It should be considered all together (what else is in the formula etc). -
I agree. Don’t automatically accept what raw material suppliers say about their ingredients. Their marketing doesn’t always reflect what happens in real life.
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ngarayeva001 said:Re formula, I am with @Pattsi and @Graillotion, the emulsification system isn’t adequate. Get a proper emulsifier. I always suggest Arlacel 165 (ala lotionpro 165, aka Glyceryl Steatate+ PEG-100 stearate)
I use the 165 series on two of my products. Quite simply the easiest to use, and most stable….sometimes we say ‘bullet proof’ as an emulsifier. And in both cases I use a strong co-emulsifiers to support it. In all but one case I back up my primary emulsifier with GSC (Glyceryl stearate citrate). Please don’t confuse that with Glyceryl stearate! Of course I also support the overall emulsion with fatty alcohols (different ones for different applications).
Tip: You emulsifier of choice…will have a dramatic effect on the feel of your product. If you choose an emulsifier that is not elegant to start with, it becomes much more difficult to formulate ‘elegance’ back into it.
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Are you sure you should heat Tetrahexyldecyl Ascorbate and Bakuchiol to 80°C, if my memory’s not wrong, it is not over 75°C and very briefly, you should check the spec sheets.
sorbitan stearate alone? - HLB around 4.7 would be water-in-oil
if you want clean(?) emulsifier, Hydrogenated Lecithin works better than Lecithin.
you might get 2 years stability with proper formulation.
maybe try Hydrogenated Lecithin + Magnesium Aluminum Silicate + GumsThere’s a brand (the brand with the mushroom), you can look it up for guide line, but i personally don’t like the texture.
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Thank you, all.
@Pattsi
Lotioncrafter says (citing the manufacturer, allegedly) that tetrahexyldecyl ascorbate can go up to 80 degrees C, but perhaps I should just add it in cool down? But if I add both that at 3%, along with 3% ethanol (a possible addition), at cool down, that might be a bit much for my formulation to handle. For the bakuchiol, all I see is to “avoid prolonged heating above 75 degrees C.” I basically just heat until 80 degrees and then blend blend blend, but maybe I am hurting the actives?Thank you.
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