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Oil seeping out/syneresis of anhydrous ointment
Hi all, I encounter a problem with formulating an analgesic anhydrous ointment. The oil seeps out from the ointment (syneresis?), which I suspect is due to temperature fluctuation. As I lived in a tropical country, the temperature can be quite hot and humid at time. Below is the formulation I am testing now in % w/w :
Petrolatum 11.45%
Fully refined paraffin wax 25%
Microcrystalline wax 5%
Stearic acid 5%
Methyl salicylate 23.5%
Camphor 5%
Menthol 10%
Nutmeg essential oil 5%
Eucalyptus essential oil 10%
BHT 0.05%
Do you think this happen because of the liquid content (methyl salicylate, EOs) of this formulation is too high, which contribute to the oil to seep out more easily? Does increasing the thickness of the ointment by increasing stearic acid helps to hold the oil content? Or other suggestion that can improve the formulation without decreasing the liquid content.
Thank you for any suggestion.
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1 Reply
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Did you type ‘syneresis’ into the search bar? This topic has been covered numerous times. 🙂
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