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Emulsion losing viscosity
Good afternoon,
New to the forum, first post.
I have an emulsion that I produced on 8/24 that is losing viscosity. I created an identical (within margin of error) emulsion on 8/31.
The emulsion from 8/24 has lost viscosity. Both emulsions sat side-by-side in a temperature controlled environment. The second emulsion is in an identical state as when I transferred it on day two.
They are creams:
66.6% H2O, 4% Glycerine w/xanthan gum
15% Oils (mct and shea butter with small percentages of jojoba and sweet almond)
5% olivem1000 with stearic acid, glyceryl stearate and cetyl alcohol that bring the emulsifiers to 10%
2% isoopropyl myristate with optiphen and vitamin E added after cool down
The only difference between the two is that the oil phase got very hot, perhaps 110*C on the emulsion losing viscosity… this is R&D so I rolled with it.
Could this heat denature the oil phase in some way. The one in question is certainly a lotion now and not a cream.
Thanks in advance
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5 Replies
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hi there
Several things could have happened.
Can you tell if it is a W /O emulsion or an O/W emulsion and if both are the same kind of emulsion?
Sometimes Olivem 1000 tends to build both kinds of emulsions depending on the water and oil content. HLB is around 8 which makes it versatile even if the supplier claims it is mainly for O/W emulsions I myself made a W/O Sunscreen and a O/W Body lotion with it. However, the speed at which you put either the oil phase into the water phase or the Water phase into the oil can have significant effects on the system that will show maybe a few days later.
Did you cool both in a similar way (stirring homogenization process during the cooling phase?)
If you Homogenize one, for example above 50 °C and one lower than 50 °C your Cetearylalcohol can build different structures which can lead to different viscosity results.
Another reason can be the Dropplet size of your formulation did you look under a microscope if the dropplet size is the same for both formulations after that period of time? maybe one is building bigger droplets because of lower sheer during production or some other minor difference in the production process. If so, you can try if the viscosity gets back up again if you homogenize the lower viscosity one.
it is not an easy problem if you make everything in the same way. maybe someone else has more ideas ????
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This is interesting. Thank you for the insight about homogenization temps. Both samples were produced with similar, albeit not identical processes. Reason being is that when I overheated the oil phase for the sample that is now less viscous, I let it sit a while until it was around 105C and blended into the water phase at 60 to balance the temp out. My normal method is to combine when both are within 10C, add steadily while homogenizing and pulse periodically as it cools to 40C in a water bath. I am thinking this is likely the key difference. I have found this formula to be fairly forgiving as far as how quickly I add the oil phase, how long I homogenize, etc. Both homogenization processes began immediately when blended at 70-80*C, but I can see adding the 105C oil phase to the 60C water phase being a shock to the structure building agents. Perhaps even the xanthan gum, which was dispersed throughout the water phase, could have been damaged. It is certainly interesting, as the formula has been stable any other time I have tested it and this iteration is as near identical as practically possible. The only thing different in the process was the temperatures.
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It should be oil in water… but the ratios of the two samples are the same. I am really wishing I had kept a sample of the thinning batch in glass.
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Glyceryl stearate and Cetyl alcohol are not emulsifiers, but structuring agents. Same for Stearic acid (unless you neutralize it? This, and the fact that we don’t know the polarity of your oils, might be leading to an instability of your emulsión. One of the samples was more stable perhaps due to higher mixing time/speed or different cooling rate. I’d put both samples in the oven to see if they are stable, and run my calculations again to see if I have enough emulsifiers (and the right one) for the oils you have.
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Right, thanks for the clarification there, I just mean the “portion” of the oil phase without being too specific.. the portion of the oil phase comprised of emulsifiers and other surfactants/structure modifiers. As to the polarity of oils, I am not too concerned, as this is the only batch I have had shift from normal. One other thing I will add, the sample in question was stored in stainless steel, and the small portions I pulled to dose with fragrance for testing seem to be reacting with the “galvanized” tins they are in… Do you know if that might be an issue? Perhaps the steel is contributing an ionic charge to the emulsion? PH is at 5.5 +/- .5
The sample stored in glass is holding up great, but at this point its only correlation.
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