All of our lotion bases are formulated to accept up to about 5% of additional oils, extracts, or fragrances by weight, including small amounts of silicones like cyclomethicone. This is because our lotions have an emulsifier surplus, meaning there is more BTMS-50 in the lotion than needed, ready to mix in extra oils.
The easiest way to add oils is to bring a measured amount of your lotion base up to about 110-130°F (43-54°C) until it begins to liquefy,1 add the calculated amount of your desired liquid ,2 and stick blend until smooth. Finally pour into bottles and let sit, uncapped, for 24 hours.
If you are having trouble mixing in additives, there are two options; firstly, bring the lotion up to its max temperature of 130°F, then add your oils, finally continue stick blending until lotion begins to re-solidify/thicken, and then pour. Second, you can add a small amount of Polysorbate 20 or 803 to your additive to help it emulsify in.
Three things of note:
A stick blender is the best thing to create a homogenous product, using a spoon or a whisk does not disperse oils as finely or evenly, causing small droplets in the lotion that begin to combine and “sweat” out over time.
Water based products like aloe vera gel or hydrosols do not need the additional emulsifier, they will, however, thin your lotion and still need to be dispersed just as finely.
We use enough of a high quality preservative that no one should be able to add enough ingredients to need more; however, each heating cycle hurts the preservative, as does the time you keep it hot. Should someone destroy their preservative (such as through boiling the lotion), heat as directed earlier, and blend in .5% additional Optiphen, then send for microbial testing. In doing this, however, all extracts will be destroyed and shelf life until rancidity will be greatly reduced, generally it is not recommended because of that.
1Do not exceed 130°F or you risk destroying your preservative! Different lotions liquefy at different temperatures.
2 Some additives (like fragrances) have max usage rates, others destabilize the lotion at high amounts, take care not to use too much and risk breaking your lotion. Up to 5% does not apply to everything and is more a rule of thumb.
3Polysorbate 20 for essential oils, Polysorbate 80 for heavier fixed oils, see our web pages for their specific usage rates.