-
Help with natural deodorant stick problem
I have been experimenting with different natural deodorants in cream formulas and found that magnesium chloride and sodium bicarbonate both seem to work well. I wanted to incorporate one of these ingredients into a deodorant stick but I am running into some problems. I have been making a deodorant stick base with propylene glycol, water and sodium stearate and it seems to have a nice consistency. However, if I try to add either baking soda or magnesium chloride to this solution, I can’t get the sodium stearate to dissolve. If I dissolve the sodium stearate first and then add the baking soda, the baking soda will dissolve and then a few seconds later something precipitates out of the solution. I know arm and hammer makes a deodorant stick with a very similar formula so it seems like in theory this should be possible. Any idea what could be going on here and how to work around it?
-
6 Replies
-
Well it depends on how much you put baking soda (I’m assuming you dissolve it in water)
-
Try heating your solution.
-
You can’t use more than 0.10% or so of baking soda with sodium stearate sticks.
-
OK, good to know. Do you know why you can only add 0.1%? What is the reaction that is taking place?
And yes I am dissolving about 2% baking soda in a mixture of water and propylene glycol using a double boiler.
-
My thinking is that the Sodium Bicarbonate (NaHCO3) preferentially pulls the sodium ions from the Sodium Stearate, yielding Sodium Carbonate (Na2CO3), water, and Stearic Acid, which is what’s precipitating out (because Stearic Acid isn’t water soluble).
In practice, tiny bits (0.10% or less) of Sodium Bicarbonate don’t seem to affect enough of the Sodium Stearate to destroy the structure of the stick, possibly because an excess of base is used to formulate most of them. I highly doubt that Arm and Hammer uses much more than that.
Pro tip: If you’re making commercial quantities, it’s a lot cheaper to make your own Sodium Stearate from Stearic Acid and Sodium Hydroxide.
-
Thanks, that makes sense. And yes I think you’re right about the Arm and Hammer product not having much baking soda in it. It’s listed just before the fragrance ingredients.
Log in to reply.