Problem with pH & viscosity in Natural Olive oil Bodywash Formula

I am trying to formulate my own natural olive oil bodywash. I am at the point where I'm having problem with pH adjustment because when I add 0.5% citric acid, it becomes watery instantly. Current pH is 8-9 and I want to reduce it to preferably pH 5.5. I got the concentrated olive oil liquid base soap from the store, so I don't really have an idea of the percentage. But here's the ingredients:

Olive oil liquid soap base:

Aqua, Sapofinied Olive Oil, Glycerine, Potassium Citrate, Citric acid

Dilution with distilled water: 1:5

To increase foaming & viscosity I add:

1. Cocamidopropyl Betaine 6%
2. Coco glucoside 3%
3. Lauryl Sulfoacetate 1%

and Fragrance 2%.

Here's where the problem lies, the pH is too high and makes my skin dry too. I can't seem to fix the pH with citric acid (0.5%) because it ruined my bodywash viscosity which I already liked. How can I fix this?

Thank you all :smile:

Comments

  • PerryPerry Administrator, Professional Chemist
    To fix it, you are going to have to first get rid of the liquid soap base then make the product using Water, Betaine, Glucoside and Sulfoacetate. You'll also probably need a thickener and a preservative.

    By definition, soap has a high pH. When you lower the pH, you reverse the chemical reaction that produces soap and it will separate into its non-soap constituent parts. You can't make soap at a low pH.

    If you want a mild, low pH body wash...don't use soap.
  • Thank you for replying @Perry ; :)

    I have somewhat managed to lower the pH to 5.5 and increase its viscosity using the same ingredients, by slightly changing the sequence of addition (CAPB to the last). 


    %
    1. Aqua48.9
    2. Sodium Lauryl Sulfoacetate      1.0
    3. Coco Glucoside  2.0
    4. Sodium Lauroyl Sarcosinate  6.8
    5. Olive Oil Liquid Soap Base  9.8
    6. Fragrance Oil  2.0
    7. Citric Acid  0.2
    8. Cocamidopropyl Betaine29.3

    Although I have noticed, when I stir gently, the color is cloudy. But when I stir harder, it becomes very foamy and after a few hours when the foam is gone, it becomes crystal clear. Why is this? 

    Another thing, I can't seem to make the smell retains stronger & lasting on skin after rinsing. But the smell during shower is so strong like typical commercial body wash. What can I add to improve this?

    Thank you.
  • You have somewhat managed to lower the pH to 5.5? What does that mean? That seems like a low target pH for a product containing 9.8% soap. 

    Fragrance oil is hydrophobic so it will tend to migrate to the micelles formed between the surfactants and water in the shower rather than deposit on the skin.

    As far as a way to correct this, I am currently studying encapsulation of fragrances but in no way do I have the expertise to give advice. Would love to hear some opinions as well. 
     
  • PerryPerry Administrator, Professional Chemist
    Well, at a pH of 5.5 the liquid soap you put in your formula is no longer liquid soap but rather fatty acid emulsified by all the other surfactants in your system.
  • chemicalmattchemicalmatt Member, Professional Chemist
    Perry is right - the pH of this should be in the range of pH8.0 with that saponified olive oil in there. You also need to increase sulfoacetate, the best hydrotrope in there, and DEL coco glucosides, which contributes very little as long as you have the sarcosinate in there. Either way, I wouldn't let this one out of the lab without a preservative, which I don't see.
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