Home Cosmetic Science Talk Formulating Sodium Carbonate in liquid soap

  • Sodium Carbonate in liquid soap

    Posted by sylnyc on April 30, 2019 at 1:19 am

    Hello everyone, 

    I am getting a reaction/result that I have extreme difficulty finding information about online. I only read that perhaps superfatting may be the cause.

    I was trying to make a simple spot cleaning liquid soap and wanted to add the cleansing power of sodium carbonate to my liquid soap.

    Please bear with me I am not a chemist but I am really curious and love to learn!

    First I made this:

    100% coconut oil liquid soap with potassium hydroxide with a superfat of 5%.

    I diluted it to 1 part soap paste, 3 parts water.

    I made a solution of sodium carbonate with water to maximum solubility.

    When I combined 1 part diluted soap with one part sodium carbonate solution, it started thickening and becoming gel-like. Within 3 minutes, it turned into an opaque paste. When I spread the paste on a surface, there are still tiny bits that are more gelled.

    I tried the same process using a castile soap from creatingcosmetics, also 100% coconut oil without superfat. I got the same reaction with this store bought diluted potassium cocoate 40%.

    My questions are:

    1. What is the thick white paste that results from this combination? Is it some form of soap? What is being transformed into what?

    2. I really want to know if liquid soap and sodium carbonate are ever mixed together intentionally for any application? Any uses or precedents?

    3. I actually find the resulting thick paste interesting and it can be cosmetically elegant. When mixed thoroughly it becomes a fluffy light cream paste that blends well with exfoliants to make a scrub and holds additional oils well. Should I stay away from using sodium carbonate in a body scrub?

    Thank you in advance, any help would be so greatly appreciated!

    Syl

    sylnyc replied 4 years, 10 months ago 3 Members · 3 Replies
  • 3 Replies
  • gunther

    Member
    April 30, 2019 at 2:14 am

    Carbonate has no use in soaps, it is often added for 2 purposes:

    1 To make increase the formulation pH. Soap is already too alkaline, so you don’t need it.
    2 To work as an abrasive to help with cleaning.
    Only undissolved carbonate crystals will work as an abrasive. Sodium carbonate is very soluble, even more than bicarbonate, so you’d need a quite lot of it for abrasiveness, likely destabilizing the formula.
    Stick to nonsoluble fine grinded abrasives, if needed.

  • belassi

    Member
    April 30, 2019 at 3:33 pm

    Potassium is two above sodium in the EC table. Possibly a replacement reaction producing insoluble sodium cocoate.

  • sylnyc

    Member
    May 13, 2019 at 6:51 pm

    Thank you very much Gunther and Belassi for your answers. 

    I do not want it to be abrasive Gunther, I was trying to make it more cleansing/degreasing. I wanted to create a product to clean makeup sponges, it cannot be abrasive otherwise it can ruin the sponges. If it was a dishwashing product then yes the abrasiveness of the crystals would have been welcome!

    In any case, thank you for the information and your time.

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