February 9, 2013

pH Drops & Curing Soap

We've talked in the past about how much we love pH drops, but we recently got a question from a student that we thought deserved space on the blog, too. Check it out:

pH drops doing their magic -
the soap on the top is fine & on the bottom is lye-heavy

Hi Lori, I had a quick question. I made soap on 11/7 and when I tested the ph today (11/20) with phenolphthalein it was completely clear, showing no pink. I am assuming this means it is safe to use even though it has not been the full 4-6 weeks. Is that right? Thanks, Laura H.

Curing Soap

Hi Laura, Great question! Yes, your instincts are correct.

If the pH tester drops appear clear (show no signs of pink), and the soap looks good & uniform with no white crystals or crumbly parts, it should be completely safe to use. In fact, if your soap recipe was formulated correctly & no errors were made during the weighing, all the lye should be gone (used up during the saponification process) by the time the soap has hardened.

If, however, the soap was not formulated correctly & there is excess lye, the drops will always appear magenta or pink. That's why the drops are SO useful to have around... just in case! For that one batch out of 20 where something doesn't look quite right, test it & see. I'd rather use a few drops of inexpensive fluid instead of burning my tongue with the ol' tongue test. Been there, done that.

However, it is still a good idea to let the soap sit for 4-6 weeks. This full "curing" process is not only about allowing the saponification to completely finish, but also about letting the soap breathe. The remaining water will evaporate, which means your soap will be harder & last longer. Who wouldn't want that? Enjoy your soap! ~Lori


Pam said...

If you have soap lying around that is 3 months, 6 months or even 1 year old compare them in the sink or shower. I find the longer a soap cures the performance gets better and better. IE the bubbles stabilize, the creaminess is more apparent the performance is enhanced. JMO

Lori at The Nova Studio said...

Hi Pam! Great point - thanks for sharing :)