Home Cosmetic Science Talk Formulating Slow darkening in a phospholipid emulsion

  • Slow darkening in a phospholipid emulsion

    Posted by Avick on July 8, 2014 at 10:40 am

    Greetings, fellow formulators!

    Ok, so here is my story for today-

    I’ve created an emulsified product using phospholipid-based emulsifiers, and also including lysine, vitamin C, and several botanical oils and botanical extracts including St. John’s Wort and arnica. The pH of the water soluble phase is around 5.5 (adjusted up with NaOH). I’ve been “field testing” this product, basically subjecting it to the abuse of life in the summer in the south, leaving it in my hot car, in the sun, etc. The emulsion is a lamellar one and although I have not seen signs of separation, I have noticed that the product darkens noticeably over a period of about 4 weeks.

    The product is preserved with BHT as an antioxidant and benzylalcohol DHA as well as two essential oils (tea tree and peppermint) as anti-microbials. I have done simple dip-stick testing for on the most abused samples and they come out clean for total aerobic and yeasts and molds. What do you think could be causing the darkening?

    Thanks for your spirit of collaboration!

    Avick replied 9 years, 11 months ago 4 Members · 7 Replies
  • 7 Replies
  • pma

    July 8, 2014 at 11:41 am

    The vitamin C… It’s very hard to avoid vitamin C oxidation. 

  • Bobzchemist

    July 8, 2014 at 12:35 pm

    “The vitamin C… It’s very hard next to impossible to avoid vitamin C oxidation. “

    Fixed that for you… :)
  • Avick

    July 8, 2014 at 1:50 pm

    Haha, thanks you guys!

  • OldPerry

    July 8, 2014 at 4:34 pm

    You’d better check your preservative system too.  That doesn’t sound robust enough.

  • Anonymous

    August 9, 2014 at 5:02 pm

    Would you mind telling me where you obtained the phospholipid emulsifier?

    Thanks in advance

  • Bobzchemist

    August 10, 2014 at 6:37 pm

    Resources of Nature 

    Lucas Meyer 
    also,plain lecithin.
  • Avick

    August 18, 2014 at 11:50 am

    Yes, thanks Bob. I just saw this post. Lucas-Meyer has a great selection of phospholipid emulsifiers with great skin feel.

    @Perry, would you have any recommendations for a secondary broad-spectrum preservative? We haven’t subjected it to challenge testing yet so I can neither confirm nor deny your allegations. ;)

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