How To Properly/Safely Conduct The Zap/Tongue Test

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Staff member
Feb 11, 2008
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Right here, silly!
For reference, the following list of instructions on how to properly conduct the zap/tongue test is a paraphrase of the procedure as taught by Dr. Kevin Dunn in his highly esteemed book, 'Scientific Soapmaking' (on page 75):

1) Take a gloved finger and wet it.

2) Rub the wet finger over the surface of your soap to gather up a coating of diluted soap/lather (does not have to be frothing).

3 Very carefully touch the lather on your finger to only the very tip of your tongue - i.e., behave as if your finger might be covered with something gross or dangerous, instead of covered with something delicious like chocolate. Don't go licking the bar of soap itself, and don't go rubbing your lathered finger all over your tongue. Just a quick touch or 2 of your lathered finger to the very tip of your tongue is all it takes to be able to detect excess alkali/unreacted lye in your soap, which will make itself known by a zapping or stinging sensation on the tip of your tongue.

4) Repeat the above on each side of your soap.

5) Rinse your mouth out with water (or lemon juice if you desire) and spit.
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