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Centrifuge test failed for cream emulsion
Hii everyone,
I have prepared a cream formulation and did centrifuge test at 3000 rpm for 30 min. For this, a very thin layer of oil is seen on top for one of the samples while for my other sample clearly 2 phase is visible (difference is in the type of emulsifier/surfactant used). How, in your opinion, I can fix it? Where am I going wrong? Also, please suggest a thumb-rule for oil:emulsifier ratio as I cannot find a detailed and thorough information on it. Would highly appreciate your insights (the great formulators here 🙂 )
Below is the composition of the sample with thin oily layer (active matter):
OIL PHASE:
CCT (triglyceride): 12%
Surfactant with HLB 11: 5%
Cetearyl alcohol : 2%
stearyl alcohol: 4%
Shea butter: 4%
WATER PHASE:
Water: qsp
Glycerin: 5%
xanthan gum: 0,4%
COOL DOWN PHASE: Preservative + Perfume + Vit E = 2,3%
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This discussion was modified 1 week, 4 days ago by
nshu_14.
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This discussion was modified 1 week, 4 days ago by
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23 Replies
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Have you thought of formulating a face oil instead of a cream? In my 20+ years experience as the co-founder and Master Formulator with a brand I founded in 2006, oils are more effective and less problematic.
The key difference with oils is that the actives are present at a much
higher concentration as they’re not diluted. This means they have a more
tangible effect on the skin. And, there is no need to add synthetic preservativres which for some can cause skin irritation.The face oil products I formulated, manufactured and distributed globally 2006-2024 were fantastic sellers and very profitable.
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I would look to reduce your primary emulsifer percentage to around 4.5% and add some Glyceryl Stearate NSE, around 0.6% and then play around from there depending on what you find.
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Having reviewed again I would reduce your fatty alcohols in the formulation.
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Thank you @Richard I dont have Glyceryl stearate NSE, can Glyceryl stearate do the job? Also, if I include Glyceryl stearate 0,6%, will it act like a stabiliser? and shall I remove any of the fatty alcohols?
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At this stage I would not add Glyceryl Stearate. Replace some of your fatty alcohol with vegetable oil, you can even increase the shea by 2-3%.
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Increasing oil and shea butter will not lead to a very sticky/oily feeling post-application??
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Considering you’ll reduce the fatty alcohols and add more shea, it shouldn’t make a big difference.
What’s the INCI name of your emulsifier?
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To clarify, “it won’t make a big difference” was meant for the skin-feel, not the stability.
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Thank you for your answer. I am using APG as the only emulsifier. I would like to test if our APG sole is enough for the emulsion.
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Had to google APG😇- the ones BASF makes have “excellent foaming and cleansing properties”, aka a proper surfactant.
So why APG in a cream as the main emulsifier?
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Ooops, sorry I wrote the abbreviation.
Because I am curious about glucosides in emulsification and I only have those available as a “greener” option.
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This reply was modified 1 week, 3 days ago by nshu_14.
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This reply was modified 1 week, 3 days ago by
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All right, but APG is still vague: there are quite a few of them.
Also, wouldn’t that be a foaming emulsion?
@ketchito , would you be so kind to make some light here, please?
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Yeah…there’s a reason why sodium lauryl sulfate is not used as emulsifier: foam and smaller micelles. Those are two reasons actually, hehe. Foam is never good when you make an emulsion, unless you can remove it before cool down. And small micelles (because of charge repulsion) mean less ability to work as an emulsifier. If you want to use a glucoside as an emulsifier, it should be cetearyl glucoside which is part of Montanon 68. And talking about green, I’ve never found natural occurring APG’s 🤓
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Thank you🙂
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I’d also would like to know what your emulsifier is (they vary in structure despite the HLB number). Also, I wouldn’t reduce your fatty alcohols (they are your structuring agents) but would use cetearyl alcohol at 4% instead (if you’re using the 50:50 version) and 2% of cetyl alcohol. Also, I’d reduce the shea butter to 2% (butters are hard to emulsify) and your CCT to 6%.
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Thank you @ketchito. Your comments are always helpful. I will give a try to your suggestions. Do you think increasing the emulsifier to more than 5% active content would help further?
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It depends on which emulsifier you’re using 🤓
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Supposed to be stable same question which emulsfier is used?
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When oil separated, it always means your emulsifier is not enough or is not working.
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CCT (triglyceride): 12% Never used but assuming its the lipid
Surfactant with HLB 11: 5% Is this your emulsifier? If so you may have to tweak, you need the right amount for the lipid qty
Cetearyl alcohol : 2% Looks good
stearyl alcohol: 4% Ok but you don’t always need two types of fatty alcohols, this might make it too thick
Shea butter: 4% This is good amount, you can even use more but butters are fickle so you have to experiment. Depending on formula, using less wouldn’t give it a lux appeal since shea is very highly regarded
WATER PHASE:
Water: qsp
Glycerin: 5% No problem
xanthan gum: 0,4% This is sometimes too much but good for stabilizing fickle formulas
COOL DOWN PHASE: Preservative + Perfume + Vit E = 2,3% 2% is high percentage preservative and 3% is high percentage perfume and vitamin e. Make sure these ingredients are compatible with the formula and put in during the right phase. My lotions would always destabilize when I used optiphen during the cool down process, guar helped but gums can also pill.
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Hii @MaidenOrangeBlossom Thank you for your response.
I am actually looking for an answer to this question: what is the lipid to emulsifier ratio one should consider for the beginning (just a general rule of thumb)?? Somewhere I read emulsifier should be a quarter to oils/waxes and somewhere it says something different. Would you please elaborate on this?
Emulsifier: Yes thats my sole emulsifier. Would you please also suggest which direction to take from here as I am getting lost. 🙁 Also I have different fatty alcohols so I am tempted to use more than one (stearyl alcohol, glyceryl stearate, cetyl alcohol, cetearyl alcohol, stearic acid). What do you suggest how to make a choice?
Cool down phase: its not 2,3% , by mistake its 2.3% in total for the whole cool down phase. so 1.5% for preservative, 0.3% perfume and 0.5% vit. E I am using.
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Thats a rough starting point but there are variables. Some ingredients like hyaluronic acid are less stable in terms of emulsifying, so you might need more emulsifier. Or you might need a different type of emulsifier, co emulsifier, stabilizer like gums etc. What texture were you trying to achieve? Different combinations of the above mentioned can result in extreme variance of basic form and feel. For example across the board I prefer using BTMS as my emulsifier. I’ve never had an issue with texture, it works well in everything. You generally need so little that along with either a co emulsifier or stabilizer like a thickner, I can make anything. The only caveat is that I have never had it tested in a lab for stability. Only testing was literally using it for years.
Also the sheer and when you add ingredients can highly affect a formulation. Like I mentioned, most of my preservatives destabilized emulsions so I’ve had to ask the forum many times when to add but it still didn’t help much so I had to include more emulsifier which can thicken a formula. Then I added a gum which helped so you can see that a good starting point in determining why a formula is unstable is to test the emulsifier first by adding a little more or trying a different one. Thats just the starting point though. Hope it works.
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Hi,
Yes, there is a “rule of thumb” which works as a start for most emulsifiers, and that’s exactly what you have read: 1:4 (emulsifier to oils). Meaning one can start there, and then tweak according to what one wants to achieve.
Regarding the use of APG, you have your answer from @ketchito in the thread above.
Anyway, considering the science, I wouldn’t continue on this route: when making an emulsion/cream, the obvious choice is an emulsifier, not a surfactant.
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