Ethanol as a broad spectrum preservative

Hello everyone :) ))))) I am trying to repeat the Weleda cream for sensitive skin and I want to use Ethanol as the only preservative in it. My question  is how much of Ethanol I need to add to emulsion to have a broad spectrum preservation system and what ° ethanol should be??? And i am sorry in advance if this question sounds stupid for someone!! I am not a chemist))))) :'(

Inci Weleda:
Water
Prunus Amygdalus Dulcis (sw.almond)oil
Alcohol
Glyceryl Stearate SE
Hydrolyzed Beeswax 
Prunus Domestica Seed oil
Glycerin 
Xanthan gum
Lactic acid

Comments

  • PerryPerry Administrator, Professional Chemist
    edited February 3
    You need at least 20% ethanol to be a preservative. But a significant problem is that ethanol is classified as a VOC which generally puts it in violation of environmental regulations if you use it at that level in something like a lotion.
  • Perry said:
    You need at least 20% ethanol to be a preservative. But a significant problem is that ethanol is classified as a VOC which generally puts it in violation of environmental regulations if you use it at that level in something like a lotion.
    Thank you Perry!!!! So you think that Weleda use less than 20%?? Can it work that way in this formula???because I don't think that they are using more than 20%of almond oil!?
  • PharmaPharma Member, Pharmacist
    20% with regard to the water phase. Also, in combination with glycerol and a low pH, less might work.
    Say you'd have 50% water, 6-8% ethanol, and a few % glycerol at pH 4.5 should be enough to stop anything from growing (not killing any microbes but just stopping them from growing).
  • Pharma said:
    20% with regard to the water phase. Also, in combination with glycerol and a low pH, less might work.
    Say you'd have 50% water, 6-8% ethanol, and a few % glycerol at pH 4.5 should be enough to stop anything from growing (not killing any microbes but just stopping them from growing).
    Thank you Pharma for your answer)))))))
  • If you are trying to keep to environmental regulations and go natural you can use ethanol that is produced from grains and is just called Bio-ethanol.
    Why do you only want to use ethanol as your only preservative. If you have to use up to 20% as Perry suggested, then this would change the viscosity, have you tried it out yet.
    Please let us know how you go? Cheers Catherine
    Dr. Catherine Pratt
    (B.Sc with HONS I , Ph.D Analytical/Organic Chem and Microbiology), Cosmetic Chemistry IPCS)
  • If you are trying to keep to environmental regulations and go natural you can use ethanol that is produced from grains and is just called Bio-ethanol.
    Why do you only want to use ethanol as your only preservative. If you have to use up to 20% as Perry suggested, then this would change the viscosity, have you tried it out yet.
    Please let us know how you go? Cheers Catherine
    Thank you for your answer,  Dr Catherine Pratt!
    I just want to copy the Weleda formula, that's why I use only ethanol. I will try to use it at different % to see how it goes!!
  • PhilGeisPhilGeis Member, Professional formulator
    If you are trying to keep to environmental regulations and go natural you can use ethanol that is produced from grains and is just called Bio-ethanol.
    Why do you only want to use ethanol as your only preservative. If you have to use up to 20% as Perry suggested, then this would change the viscosity, have you tried it out yet.
    Please let us know how you go? Cheers Catherine
    The regulations I think Perry addressed focus on VOC's as chemicals and do not exempt "Bio-ethanol".  Example: California's ARB regs - don't think they've placed regulatory limits on VOC's from lotions at this point.   Most other states and the feds follow some aspect of California's.  https://ww2.arb.ca.gov/sites/default/files/2020-12/cp_reg_article-2.pdf
  • PerryPerry Administrator, Professional Chemist
    @PhilGeis - yes, I don't know the regulations exactly but I recall that styling gels were included and when I was formulating, there was movement on including shampoos, moisturizers, and other personal care products. Not sure where the regulations stand at the moment.

  • PhilGeisPhilGeis Member, Professional formulator
    edited February 4
    Thanks Perry - maybe not yet - but if CARB thinks it a source (and 20% will look significant) , they'll place a limit. 
  • PhilGeisPhilGeis Member, Professional formulator

    Perry, an obscure historic regulatory problem with ethanol.  Think 1989 or '90, shortage of SD40 alcohol disrupted the industry – we couldn’t make hair sprays and gels and alcohol deodorants. 

    Issue - noncompliant SD40 alcohol.  Brucine (SD40 denaturant aka dimethoxy strychnine) included impurity strychnine > ATF standard.  World’s brucine supply from a few plantations (from seeds of nux vomica tree) in India came via a single supplier, and alcohol suppliers apparently no paid  attention until crisis.  No idea why supply that one year was off – not reported before or since.


  • PerryPerry Administrator, Professional Chemist
Sign In or Register to comment.