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Serial dilution of a cream?
I want to find the smallest % I can use in a cream formula, of an oil, and still obtain the good qualities in the cream that the oil confers.
Do I have to make separate batches of the cream, with say, 1%, 2%, etc to 10% of the oil OR can I just make a cream with 10% of THAT oil, and a cream WITHOUT that oil, then just mix the 2 creams in the appropriate amounts to give me final concentrations of 1%, 2% etc oil in the final mix?I would of course make the 2 creams at the same time, then mix the appropriate mass of each cream into a new container to create a different total % of the oil in the final mix.I ask because I am not experienced enough to know if maybe this is something that is NOT recommended with emulsions, because they are more complex that just a simple solution, with which we CAN do serial dilutions.I hope this isn’t a stupid question I’m asking. -
1 Reply
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It’s not a stupid question - it’s a great question!The answer, though, comes down to the role of emulsifiers. If you make 2 creams, one at 10% oil and one at 0% oil, but both with the same amount of emulsifier that keeps the batch stable at 10% oil, that will give you a set of information that only relates to having more emulsifier than you need at lower oil percentages.If you make 2 creams, one at 10% oil and one at 0% oil and 0% emulsifier, that will give you a set of information that only relates to having the same emulsifier:oil ratio at all oil percentages.BUT…if you make 3 creams, one at 10% oil, and one at 0% oil with the same amount of emulsifier, and one at 0% oil and 0% emulsifier, that will give you a much wider set of information, since you can make a number of combinations that vary the emulsifier:oil ratio.It all depends on how involved you want to get at this. Since these are complex systems, though, this whole set of experiments should just be a guide for you to determine what level of oil you want. Once you’ve decided that, you should make a full-sized batch and run stability on it, then adjust the formula if needed.
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