Home Cosmetic Science Talk Formulating aerated batch with Na-Stearate

  • aerated batch with Na-Stearate

    Posted by joseg on March 8, 2014 at 11:51 pm
    I have this cream with stearic acid @ 2% that when cooled down to 40°C, it looks too aerated (specific gravity= 0.95).  
    My initial pH is around 4, so I have to adjust with around 0.10-0.15% NaOH (25% solution). Without wanting to, I’m forming soap which I think is the cause of this aeration.
    Any advice when making in situ emulsifiers to prevent this aeration? Add NaOH when combining phases or at the end, does it make any difference?
    Thanks in advance.
    joseg replied 10 years, 2 months ago 2 Members · 4 Replies
  • 4 Replies
  • Bobzchemist

    March 9, 2014 at 12:37 pm

    If you don’t want to create soap, why are you adjusting pH at all? Where is your final pH ending up? Lastly, what do you think you would be accomplishing in your cream with un-neutralized stearic acid?

    And a processing note: Aeration only happens when you pump air into a product, regardless of how much soap is or isn’t in the formula - unless you’ve got something strange going on, gas bubbles do not spontaneously generate. You need to change your agitation/processing methods so that you incorporate less air, particularly during cooldown.
  • joseg

    March 9, 2014 at 1:34 pm

    My final pH is 4, that’s why I need to adjust. I have stearic acid there just for the thickness. 

  • Bobzchemist

    March 9, 2014 at 10:28 pm

    At pH 4, all stearic acid soap reverts back to stearic acid and caustic. Chemically, it is not possible for any fatty acid soap to exist at that pH.

  • joseg

    March 9, 2014 at 10:39 pm

    sorry…I meant to say my final pH without any adjustment is 4, then I want to adjust it to 5.5-6.5

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