Question on using Phenolpthalein

[lisafrantz]

I'm new to CP soap making and decided to use Phenolphthalein to test my soap. I had referenced a soapmaking book and it said to put a drop or two on the soap to test and online there were other suggestions of dissolving the soap in distilled water first or dissolving in 50/50 distilled water/alcohol. I tested 3 batches--1 that has been curing for 5 weeks, 1 that has been curing for 4 weeks and 1 that has been curing for about 2.5 weeks. When I put the phenolphthalein on the soap I got a clear result on all 3 batches. When I disolved the soap in water, I got a fuchsia result; when I dissolved it in the 50/50 mix it was clear. I decided to test a store purchased bar soap in the same manner with the same results. Anyone out there using phenolphthalein that can tell me which is the right way to do this testing so I can quit worrying that my soap is not safe? I do understand that all 3 soaps need to cure a bit yet, but just wanted to test out how the phenolphthalein works. Thanks.

[MarieJeanette]

Here is a trustworthy site with info on how to use phenolphthalein: https://summerbeemeadow.com/content/phenolphthalein-ph-and-soap

From what I understand, phenolphthalein works best in liquid solution. My notes that I've collected over the years say that dropping it onto a dry bar of soap is useless because the results will test out clear. And if the soap is wet and you drop some pheno on it, although it will turn a pinkish/reddish color (since, after all, soap is alkaline), you won't really be able to determine the level of alkalinity because it's difficult to gauge the depth of the color as it sits on a bar of soap. It's much easier to gauge the depth of shade if it's in a liquid suspension.

HTH!

[lisafrantz]

Ok, thanks I wasn't able to access the site or find Summerbee Meadow online but I'll keep looking. There is lots of info out there.

[TallTayl]

Be very careful when using pheno. Gloves and eye protection at a minimum. And don't add it to the main batch of what you are testing, or even to a bar of soap you intend to use later. Always pull a sample off and do not recontaminate the batch.

http://www.btps.ca/files/PDF/MSDS/Phenolphthalein_Indicator_Solution_528.00.pdf

http://avogadro.chem.iastate.edu/MSDS/phenolphthaleinsolution.html

http://avogadro.chem.iastate.edu/msds/phenolphthalein.htm

All that said... Testing for free lye in a finished, cured bar soap is very simple and safe. Wet a finger, rub it on a soap surface, then touch the soaped finger tip to your tongue. Zap, free lye. No zap, no free lye. This is a much more reliable test than pheno which may or may not be used correctly. You will know if you get a zap as it will feel like you are licking a 9 volt battery.