Alternatives to propylene glycol as a salicylic acid solubilizer?

edited July 2014 in Formulating
Propylene glycol solubilizes salicylic acid at an about 7 to 1 ratio, but are there other good alternatives?


  • SD Alcohol
  • Would be helpful to know what type of product it is going into.
  • Damn I forgot I had posted those tables before, no formula yet, just wondering about solubility and if there are any good direct replacements to PG.

    Here's the sorted data, can share spreadsheet if needed.

  • Well, suggestion really depends on the type of product and other chemicals you can use.

    SLES if you heat it first
    Add sodium citrate to your water first will help solubility
    Adjusting pH up will help depending on what your final pH will be
    SD alcohol

    There is a start for ya.
  • edited July 2014
    Thanks, when you say help re sodium citrate and adjusting ph, do you have any (ballpark) numbers on that? :)
  • I have solubulized SA numerous times. Just takes a little practice and getting the right solute. I will say I have used the Salvona SalSpheres product successfully in the past and avoided the whole issue. It is a bit $$$ but it does have less irritation and is incredibly easy to use. So easy a marketer can use it..... Microformulation Cosmetic Consulting provides Custom Formulations for both large Commercial accounts as well as smaller entrepreneurs. We can provide Naturally compliant Formulations under the NSF, NPA, Whole Foods and USDA Organic Certifications.
  • To add to the above, some more solubilisers:-

    - isopentadiol,

    - betaine (this isn't cocamidopropyl betaine)

    and buffer (using citric acid and sodium citrate) to a pH of 3-4.
    Jane Barber & The Advanced Cosmetic Formulators Club 
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  • Without my notes which are in my office I would day try 1% sodium citrate to start.  Mic it into water first and make sure it totally dissolves. 

    Again, not to be rude but until I know what type of product you are making and your other ingredients I won't be responding to this anymore.  It would be a waste of time to throw out all different possibilities when most may not apply.
  • @davidW I agree. It really is a different exercise if it is a Shampoo, Facial Wash, or even a peel. Microformulation Cosmetic Consulting provides Custom Formulations for both large Commercial accounts as well as smaller entrepreneurs. We can provide Naturally compliant Formulations under the NSF, NPA, Whole Foods and USDA Organic Certifications.
  • @Makingskincare : Thanks! Is the choice of buffer important or only the end pH? How many g/100ml of SA is soluble at pH4? And do you have numbers for isopentadioal and betaine?

  • To revisit this issue for a specific formula!

    I'm making a water free thick "anti acne" concealer paste, and wondering if I could perhaps use castor seed oil in conjunction with alcohol to solubilize the SA, instead of say proyplene glycol?

  • Finsolv EMG-20
  • @Zink

    Hard to answer your question without some idea of what is in the water-free paste?  Is it oil based?

    You could try Octyldodecanol or 1,3-Propanediol, but it all depends on what you're trying to incorporate it into.
    Chemist/Microbiologist formulating in the Organic & Naturals arena under ECOCert/Natural Products Assn/Whole Foods/National Organic Program guidelines focused skincare & haircare products. 

    Provides Formulation Development and Lab-Scale Contract Manufacturing Services.  See website for details

  • Ah yes forgot to mention, It's oil based, I used castor seed oil and alcohol and that worked well (both are on the charts).

  • edited May 2015
    What I'm not as sure of is how effective SA is in a mostly oil based formula.
  • isoprene glycol worked well for solubilizing salicylic acid
  • IF you have an idea, try it and then let us know.
  • edited September 2017
    I know this is an old discussion, but very relevant to me.
    How have your experiments with differents solvents for the salicylic acid been going?

    I tried 20% propylene glycol with 1% sodium citrate as buffer at a pH of 4.0 - 4.2 (to 75% water). No such luck. Precipitation starts within about 5 days when I keep it in the fridge.

    Edit: I see you use castor oil and ethanol in an anhydrous system. You had no problems with it so far?
  • How much SA do you want to dissolve? What do you want to obtain? 
    Propylene glycol + ethanol + glycerine should do the job. 
  • @em88
    A BHA exfoliant with 1% salicylic acid. I have gotten a few tips I'll start working on (also keep it out of the fridge). To be continued! :)
  • Waiting for a feedback!
    Good luck!
  • I was looking up some old information on betaine today and came across the following information that may be useful to someone.

    Betafin BP20 (betaine) is a co-solubilizer for salicylic acid and allantoin.

    Salicylic acid
    •Use levels from  2  to 10  %.
    • Solubility in water is 0.2 % at room temperature
    • Betaine was found to increase the solubility of salicylic acid to 5 %

    •solubility in water 0.7 % at RT
    • Betaine was found to increase the solubility of allantoin to 2 %

  • edited October 2017
    Coincidentally I have received this information about betaine very recently, I'll order it from a supplier in the UK.

    On their site they state: "We have no empirical data on using betaine as a solubilising agent for salicylic acid but will carry out tests and publish our findings here."

    Looking forward to experiment with it and find out what % are needed for both allantoin and salicylic acid.
    If I know more, I'll let it know here on CC.
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