Fixing Layered NaOH BDG Liquid Soap

I recently received a liquid soap made by a fellow BDG soaper.

He is unhappy with his liquid because it has 2 layers. One really nice clear layer on the bottom and a really greasy opaque layer on the top.

I am going to try to work out what went wrong with his soap. I suspect it has something to do with unsaponified elements.

Notice the layer on the top of the soap. This soap was made from NaOH glycerin saponified with KOH so it has already been "Thickened". If the soap had not been thickened this layer would appear at the bottom of the soap. In less severe cases the soap would just be cloudy.

Unsaponified ingredients cloud the soap but when it reaches a saturation point the unsaponified ingredients float to the top in thickened soaps and fall to the bottom with non-thickened soaps. This process is also known as sequestering.

Sequestered material is not always unsaponified ingredients but in this case that is what I suspect.

Stay tuned... I will be attempting to "fix" this soap.

=== Updated 01/11/2010 ===

What I've found is that this soap was not fully saponified. The first indicator was the pH of the soap. The pH was really low being just above 8. A low pH doesn't always mean that you have saponifiable elements left, it's just a good indicator. Your pH could be as high as 10.5 and you could still have saponifiable elements left in your soap.

You can read a bit about pH or caustic testing your soap at Knice-N-Clean.com.

I took a sample of the soap and ran a SAP test on it and found that it needed another 2 grams of KOH caustic for the soap sample in the first photo. That is actually quite a bit. If a SAP had been calculated on the BDG prior to making the soap this could have been avoided.

You can find out more about working out a SAP for your BDG in our book "Making Biodiesel Glycerin Soaps".



Notice how the soap gets very cloudy and opaque during saponification. This is normal and will remain cloudy until saponification is complete. I hot processed (HP) the soap to speed up saponification and I was able to finish the soap with less than 30 minutes of cooking. You can also cold process (CP) the soap but it could take anywhere from overnight to a few weeks for saponification to complete.

Other indications that this soap was not fully saponified are;

• The soap felt really greasy when you washed with it.
• There was a foul undertone odor in the soap, it is possible that the soap had enough superfatting to cause the soap to start becoming rancid.
• The soap lacked a nice lather.

This is the final soap. The soap now has a pH of 10.5. It has a nice feel when washing and the greasiness is gone. The foul undertone odor is gone and the soap has a really nice lather. The soap is also a bit thicker and now is a very nice viscous gel.



Notice the clarity of the soap. It's just a bit brighter than before and has a really crisp look to it.


To learn more about soap making from Biodiesel glycerin, be sure to check out our great book "Making Biodiesel Glycerin Soaps". It contains lots of great tips & tricks for getting the best soap out of your Biodiesel glycerin. Click here to learn more.

Happy Soaping :)

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