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Potassium carbonate and liquid soap making??

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  • Potassium carbonate and liquid soap making??

    Seen a few recipes for liquid soap making that has Potassium Carbonate in it as well as Potassium Hydroxide.
    (I'm doing my research before i attempt my first batch)

    Why the Carbonate? Do you really need it in your liquid soap mix? What reaction does it give to the process?
    Also how would you calculate it in a recipe as doesn't have the option to calculate it along with the KOH

    Sorry for all the questions, just a little puzzled!!

  • #2
    Hi Suzy,

    from what I know, potassium carbonate can be added, but it is NOT necessary (I make my liquid soaps without it).

    It does not really saponify, that is why it is not in the calculation. Carbonates are very weak bases and they readily saponify only free fatty acids - there is few of them in your oils - but very slowly with fatty acids attached to glycerol (that is how they are in the oils). The reaction of carbonates with esters of fatty acids with glyceril is that slow that it takes hours of very strong heating (1-3 days) to get some saponification done. Therefore if you add it together with KOH the KOH will win the race for oils easily.

    I have read, though, that adding carbonates helps the soap to foam and to increase cleansing properties - they act as water softening agents, as they react with calcium salts of hard water, which would otherwise react with soap molecules. This way soap can foam and clean well in hard water.

    In the industry it is also used for the saponification of free fatty acids that could affect process of soapmaking. E.g. if you have oils high in free fatty acids and you add your KOH (NaOH), then these fatty acids will very quickly react and this can cause false trace or somehow seized, unevenly emulsified soap trace.

    That is all I know...
    Long live your bar of soap!
    My blog:


    • #3
      Thank you for that bit of advice. I just wasn't sure if it really was essential.

      From what i have read, it seems to be used for if you are making bigger batches, i think its supposed to make it easier to stir the bottom of the pot while you are cooking the soap mixture.


      • #4
        It does indeed make it easier to work but can be hard to get hold of and isn't necessary to the final produce.


        • #5
          I've found some on ebay but don't think i will buy any as i will prob only make a small batch for starters
          I just thought it would make the batch too harsh!!