Teach Soap

I don't understand why I've seen it said repeatedly that it's superior to testing the pH with strips. Because pH strips only work on the surface and also work within a range and so aren't super accurate.

I've tried looking this up, but I just find more entries and blog and other forum posts about how to do it and so on.

When you stick your tongue on the soap, it's still only touching the surface as a pH strip would. Do you get zapped because of the state of the surface, or is it a weird conductivity thing? Like getting zapped from there being too much chlorine in a pool? That's what I can't seem to figure out.

If it only zaps you because of the surface, I don't really see how that's any more reliable to a pH strip? It's true a pH strip can't tell you that something has a pH down to a fraction of being 8.524 rather than just vaguely in the 8 range, but at least it means that surface isn't lye heavy, and assuming there aren't any pockets or anything, neither is the rest of it. And if it's not some kind of conductivity thing, isn't that 'zap' actually a minor chemical burn on your tongue from the lye?

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"Effective questioning brings insight which fuels curiosity which cultivates wisdom"

The zap is due to the high pH. Think of putting some straight vinegar on your tongue. I find it more accurate then the pH test strips. Those only give you a range. That range might be on the lower side, so you think your soap is ok, but it still might be lye heavy. If you have some juice handy, you can rinse your mouth out with that, then spit it out.

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Irena
Closed minds are like faulty parachutes; they refuse to open.

yep, what she said!

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Remember, it's not just that we weather the storm, but how we dance in the rain.

Tammy

I know my "has to know exactly how stuff works" is showing, but lye on it's own has a pH of 12 right? And when soap is "lye heavy" that means there's too much unreacted lye? Which means that the pH would be somewhere closer to 12? Probably between 10-12 depending on exactly how lye heavy it is. So how could soap showing a lower pH of something between 8-9 also be lye heavy when most CP soaps are said to end up in the 8-10 range? pH strips range is fairly limited. Something between 8-9 is still definitely not lower than 8 and definitely not higher than 9.

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"Effective questioning brings insight which fuels curiosity which cultivates wisdom"

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Genny

In that case would a zap test still work? That's what I was getting at. If the surface of the soap is fine, but lye lurks elsewhere in it, a pH strip can't tell you that. If a zap test will then that makes more sense why it's a good practice. If a zap test only accounts for the part of the soap your tongue touches, basically the same as a pH strip, then I fail to see how it's more accurate at all.

That's the thing I've been trying to figure out but can't find the answer.

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"Effective questioning brings insight which fuels curiosity which cultivates wisdom"

I think it depends on how you're zap testing. When I do mine, I put a bit of water on my finger and run it along the soap, then touch my finger to my tongue. I do the tops first & then the cut sides.

But honestly I don't really know much about pH.

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Genny

Here's what I think... pH strips give you a range of the pH (although I am sure you could by some that are more sensitive than others) and the zap test also tells us the presence of lye in our soap - in essence a range. So the zap test gives us the same information but at a much cheaper cost.
If we wanted to be sure, then we should dissolve a portion of each batch in distilled water and use a digital pH monitor, but again it would not tell us if there is a small piece of lye hidden somewhere else in that soap. Maybe that is why we cut the loafs into bars?
I used a digital pH monitor when I worked in pediatrics - they are fun to use, but I can think of other things to spend my 50-100 dollars on.
So I check my bars closely and do random zap tests on several of them. I have stopped licking them and now use a wet finger run across different areas. My batches are small... 8-15 bars which makes the process easy to do. The only time I have gotten a zap is when I tested fresh made batter (for education purposes ) and when I checked a non-gelled batch less than 26 hours old.

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Susie
Sometimes A Mistake is so much fun, You just have to do it again!

I think the point is that test strips don't offer any more accuracy than your tongue, rather than that there is some actual scientific reason why they are no good for soap. The zap test can be a chemical burn on your tongue, but once you get to know when to check your recipes, it is not very likely to actually happen...I only make HP, and I am far more prone to forgetting that it is hot than I am to misjudging when it is still caustic.