What can I add to this formula to make it feel nicer


distilled water

81.89%



lactic acid

11.11%







sodium pca +

glycerin

5.00%



green tea extract

1.00%



<xanthan gum>

1.00%



right now it feels "OK" it absorbs but it makes my skin feel tight and shiny. I know I have a high acid in there but I need it. I was thinking of butylene glycol or propendial 1,3 or both. Also, the ph is a tad low for me it's @ 2.5 on a ph strip (my ph meter is on the fritz). What can I add to increase the ph to a 3?

Comments

  • PharmaPharma Member, Pharmacist
    A glycol sounds good and in order to increase pH, add a base (NaOH or KOH will do). Alternatively, don't add pure lactic acid but a blend of lactic acid and a lactate salt (sodium lactate). This however requires that you calculate it (knowing about buffers will help) though it won't be super accurate even with the right formula.
  • @Pharma
    just curious why do you say to add sodium lactate to lactic acid? 
  • PharmaPharma Member, Pharmacist
    A mixture of the right proportions of lactic acid with sodium lactate gives a higher pH than pure lactic acid.
  • Are you using 90% lactic acid? (I'm assuming you're trying to make 10% lactic acid). Adding sodium lactate to lactic acid would yield a higher pH than the acid alone, although you might need to add some NaOH to bring the pH up to 3 (I believe the ideal pH would be 3.5-3.8). I've made some high strength lactic acid peels with sodium lactate, and even with a 1:1 ratio, I could only get the pH up a few decimal points, but keep in mind that's with 50-65% lactic acid. 
  • PharmaPharma Member, Pharmacist
    As an example: to achieve a pH of 3.86 (equals pka of lactic acid), you'd need 1 mol-equivalent pure lactic acid and 1 mol-equivalent of pure sodium lactate. Converting molecular weight into gram gives you 1.112 g sodium lactate for every gram of lactic acid 90%.
    To calculate a different pH, use the Henderson-Hasselbalch equation and don't forget to calculate in mol, not grams, and consider dilutions if working for example with 90% lactic acid. Also, don't just add sodium lactate to your 10% lactic acid but calculate the required ratio which would equal 10% lactic acid plus sodium hydroxide. In above case, you'd have to use 5.265 g lactic acid 90% and 4.735 sodium lactate to obtain a buffered '10% lactic acid' at pH 3.86.
  • @Pharma, when you calculated sodium lactate did you assume it's 100% sodium lactate? I decided to check how my lactic buffer template works (because I am not a chemist and I put it together based on my understanding) and run your numbers and it gives me 3.55. So my formula is either wrong or you assumed pure sodium lactate.


  • PharmaPharma Member, Pharmacist
    100% sodium lactate and 90% lactic acid for a pH which equals pka.
    And shush, I mixed stuff up and posted an error: 5.528 pure sodium lactate and 4.472 lactic acid 100% or 4.960 lactic acid 90%.
    Good observation!
  • edited May 22
    oh wow, ok, thank you. Yes, I am using 90% lactic acid. So then if I am only using 4.960 of lactic acid then would that change my formula to a 5% lactic acid serum? (I rounded up)
  • @Pharma, thank you so much! It means my template works!
  • PharmaPharma Member, Pharmacist
    oh wow, ok, thank you. Yes, I am using 90% lactic acid. So then if I am only using 4.960 of lactic acid then would that change my formula to a 5% lactic acid serum? (I rounded up)
    Only if you didn't add sodium lactate and it have a higher pH than you already have. It only works if you add sodium lactate!
    Given that cosmetics is great at marketing but sucks at telling the truth, the whole truth, and only the truth, a mix of 5% lactic acid with 5% sodium lactate would probably be considered a buffered 5% lactic acid serum whereas a 10% lactic acid with 5% relative amount of sodium hydroxide would most likely be considered a buffered 10% lactic acid serum. Both will be 100% identical and, chemically speaking, be 5% lactic acid. What's sold out there is usually buffered to some extent and nobody cares that this turns the acid into a salt. Hence, call it whatever you like as long as it contains 10% lacti-something. ;)
  • @ngarayeva001
    do you mind sharing your template for me to use? I can give you my email. Thank you for considering! Also, can you work backwards? For example, if I know what I want the ph to be can I add that percentage first and then add in the lactic and lactate?
  • alan123alan123 Member
    edited May 25
    Is this meant to be a serum? 

    you can try replacing Xanthan Gum with Siligel.

    Also, I like mixing Siligel with Sepinov emt 10. However, not sure how Sepinov will deal with lactic acid. You can try mixing 0.3% Siligel 0.4% Sepimax Zen and 0.2% Hyaluronic acid High molecular weight.

    Also, you can replace sepimax Zen 0.3% with Sepinov emt 10 - 0.3%. The texture would be a bit nicer and add later lactic acid see how is behaving if it is loosing consistency go back to Sepimax Zen.

    Not thick enough..? increase %s
  • @alan123
     yes it's a serum. thanks for the advice! I'll try it. 
  • czkldczkld Member
    edited May 30
    @esthetician922 I will attach the file to the post. I have basically the same template as @ngarayeva001 ^^. Also, regarding the consistency, I also suggest Siligel. Also you could try a bit of HMW HA (it would look nicer, crystal clear. The siligel can sometimes make it kinda murky tbh)
  • @czkld may I ask where did you find yours?
  • czkldczkld Member
    @ngarayeva001
    a friend of mine who is a chemist sent it to me 
  • I think it’s my duty to warn everyone about using such templates. The math might be right but pH is extremely complex thing. This calc works on paper, but other ingredients might have significant  influence on the overall system. Acids must be treated with respect. I use this template to make acid peels for my personal use but I would never share it with anyone else. I am sure people with more experience would support me on this.
  • Sorry just to emphasize it even more, I have the least sensitive skin among everyone I know. Most people won’t be able to tolerate what I can when it comes to pH. Be very careful with acids.
  • czkldczkld Member
    @ngarayeva001 yes, I 100% agree. this is a v rough estimate and you really need a proper ph meter or at least strips to determine the actual ph in the product. I use it to calculate the buffer sometimes. 
  • PharmaPharma Member, Pharmacist
    I can only concur with both of you!
    Always measure pH.
  • yes, of course, I wouldn't use unless I measured the ph but to get a sense of how to make it higher is all I would use it for. Thanks!
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