How do you PH Test your liquid soap?

[Carl]

Do you use one of those nice digital meters (about $15 on Amazon)? If so how?
Do you put some paste in distilled and then test?
Or do you use strips?

I'm assuming if the PH is too high, you keep cooking.

Just curious here.

Thanks!!

 

[Dahila]

ph of soap will be between 9-12 . To check it you need a bit better Ph meter than the one for $15. You need to make solution 10%soap in 90% of water then check ph. No cooking will change ph. We have a few interesting topics on liquid soaps

 

[Carl]

Thanks.
So how do you check your 90/10 solution? What kind of tool?
If it's over 12, what do you do with it?

 

[DeeAnna]

http://alaiynab.blogspot.com/2015/05/ph-testing-of-liquid-soap-and-lowering.html
http://www.modernsoapmaking.com/how-to-ph-test-handmade-soap/

...If it's over 12, what do you do with it? ... I'm assuming if the PH is too high, you keep cooking.

Checking pH, even if you do the measurement accurately and with good equipment, doesn't tell you if there is excess alkali or not. For one thing, the pH test isn't sensitive enough for this determination. That's especially true with the consumer quality equipment most people use. Also the pH of a lye-neutral soap (no excess lye, no excess fat) will vary depending on the fatty acids in the soap.

To get useful info about excess alkalinity, the correct procedure is to titrate a sample of diluted soap with a standardized acid solution. You take the titration to a known endpoint and then calculate the amount of excess alkali from that information. Only then can you make any kind of educated decision about whether the soap has excess alkali or not.

Or you can zap test. While it doesn't tell you any precise numbers, your tongue is a surprisingly good "go-no go" indicator of excess alkalinity. If you follow a sensible method for zap testing (no, do NOT directly lick the soap!), the likelihood of injury from the zap test is low. (I agree with a lot of what Kenna at Modern Soapmaking says in the link above, but I don't agree with her on this particular point.)

As far as cooking longer? You need to know if cooking longer will actually do anything useful. If all of the fat has been saponified, you're wasting your time to cook longer -- there's nothing for the excess alkali to react with.

 

[Carl]

Thanks for a great answer

 

[IrishLass]

I use the laissez-faire method when making my liquid soap, which means I never take pH of my liquid soap (for the same reason DeeAnna mentioned above), and I also never cook it to the paste stage. Once my batter is at a good emulsification, I take my pot off the heat and just let it sit at room temp (covered) to do its thing and come to paste all on its lonesome, which is always does within about 6 hours or so. Then, once it has done so, I just do a simple zap test. If it's still zappy (which is actually a rare occurrence for me), I just let it sit longer at room temp (covered) until it's tongue-neutral, which normally occurs within a hour or two.

As with DeeAnna, I really like Kenna of Modern Soapmaking, but I completely disagree with her stance on the zap-test. I perform the zap-test the way Dr. Kevin Dunn instructs in his book 'Scientific Soapmaking', which we made into a sticky here.


IrishLass