Zap Test

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The Efficacious Gentleman

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It's the age old question with testing - at what pH is it bad? Does a perfectly fine Castile have the same pH as a perfectly fine salt bar? Or are you testing for excess lye instead of pH? That's a useful test for seeing if a soap is safe. pH on its own does not tell you if it is safe (IE not lye heavy)

The zap test is an easy, effective, and (when done correctly) totally safe method of testing for excess lye in soap
 

Peachy Clean Soap

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It's the age old question with testing - at what pH is it bad? Does a perfectly fine Castile have the same pH as a perfectly fine salt bar? Or are you testing for excess lye instead of pH? That's a useful test for seeing if a soap is safe. pH on its own does not tell you if it is safe ( Is not lye heavy )

The zap test is an easy, effective, and (when done correctly) totally safe method of testing for excess lye in soap
So True' as i'm learning. Dr. Keven Dunn's video above @ end after all said & testing done on how to test if soap is lye heavy' he mentions at end of video to simply do the zap test & train our selves to be able to " feel the zap & taste if soap is lye heavy' ( I'v known about this zap test' never thought to apply it to older soap ) so I thought I'd put Docts theory to test! I had a loaf other then the "pictured one above" I was in Q. about & It works! I could feel just a ever so "slight-zing" & " taste was defiantly different", Also Ive discovered why ive had a prob w/ my "heavy lye" as of late! one reason is my " super fat was to low & 2%" & my "Balance" was off on lye. As I continue on my Soap Journey I'm happy to report my last few batches have been in "Balance" regarding lye as the good Dr. Dunn refers to "weight" lol 😃😉🧼💫💞.
 
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Shewearsfunnyhat

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It's the age old question with testing - at what pH is it bad? Does a perfectly fine Castile have the same pH as a perfectly fine salt bar? Or are you testing for excess lye instead of pH? That's a useful test for seeing if a soap is safe. pH on its own does not tell you if it is safe (IE not lye heavy)

The zap test is an easy, effective, and (when done correctly) totally safe method of testing for excess lye in soap
From a chemical safety perspective, chemicals (including soap) with a pH of 11.5 or higher are considered to be category 1 corrosive substances under the GHS. They cause irreversible damage to human skin. Most cold process soap has a pH of 10 or higher. This is why it's important to have a way to test for alkalinity in soap. Its important to know if your product is safe to use especially if you decide to sell or give it to friends.

Zap tests are ok. But, they only give you information about what is happening at the surface of your soap. The pH of the surface of the bar will change over time as its exposed to CO2. The pH of the inner bar will not change much because it's hard for a gas to penetrate a solid mass.
 

DeeAnna

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If I'm understanding you correctly, you're saying the reaction with CO2 is the only reason why the alkalinity of bar soap can change over time. It's certainly a factor especially at the surface of the soap, but it's not the only reason.
 

The Efficacious Gentleman

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That's why I made a point of saying that it should be done properly.

And while I think that the GHS labels are very good and well managed in general (pretty certain there will be many exceptions) I am not sure that it's overly helpful to bring it in to it, for the following reason -

If a bar of soap has a pH of 11.5 I think something might have gone wrong and it is most likely lye heavy anyway. If a bar is not lye heavy and is in all other ways well made and a reasonable bar of soap, it is not very likely to be pH 11.5 or higher, based on the average soap being 9 to 10 on the scale.

So with the accuracy issues of how most people would test, coupled with the margin of error for layperson in interpreting the results, I still maintain that the zap test, when done right, is the best way for the majority of people to ascertain if their soap is safe or not.
 

Shewearsfunnyhat

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Kevin Dunn has great instructions on how to do it properly in Scientific Soap Making. You can easily get the chemicals needed to do it at home. (Well mostly easy, reagent grade ethanol can be hard to find due to COVID). The most expensive piece of equipment is a scale that reads to 0.00 g. The procedure is line with what the large cooperations are required to do.
 
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The Efficacious Gentleman

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Kevin Dunn has great instructions on how to do it properly in Scientific Soap Making. You can easily get the chemicals needed to do it at home. (Well mostly easy, reagent grade ethanol can be hard to find due to COVID). The most expensive piece of equipment is a scale that reads to 0.00 g. The procedure is line with what the large cooperations are required to do.
I know this. But (and it is a very big but) how many people would actually do it correctly? I can guarantee that not everyone who talks about the pH of their soap has even read anything by Kevin Dunn, let alone follow the instructions.

I'm not going to keep on flogging a dead horse here - I maintain (and you can certainly think otherwise if you want to do so) that of the two methods, the zap test is the most accessible for the vast majority of people and gives the important information - is my soap lye heavy or not.
 

IrishLass

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If a bar of soap has a pH of 11.5 I think something might have gone wrong and it is most likely lye heavy anyway. If a bar is not lye heavy and is in all other ways well made and a reasonable bar of soap, it is not very likely to be pH 11.5 or higher, based on the average soap being 9 to 10 on the scale.
A very interesting tidbit from Dr. Kevin Dunn's book in regards to pH and lye-heaviness shows how the former is not necessarily a good indicator of the latter. The tidbit was data referenced from a dermatological journal citing the conclusions of Irritatation Index tests done on a number of commercial lye-based soaps. It turns out the least irritating soap out of the group of lye-based soaps tested was actually the one with the highest pH: namely Johnson's Baby Oatmeal soap with a pH of 12.35. The most irritating in the study was Camay Gala soap with a pH of 10.36. Go figure! lol
 

Lonardlis

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Well thank you for your responses! I attribute some of this behaviour to my recent insane soap insanity - I cannot seem to stop thinking about soap - so it was foolish and I did rinse my tongue after I realized it was burning a bit. I think I was making an effort to be 300% sure there was no zap - and then when I did wait long enough to feel a sort of burning feeling - I felt convinced that must be proof they might be lye heavy.....a sign of an impending zap. But honestly, I did try ph strips - and im not sure of their accuracy - they all showed a 9/10 ph - which was different than the distilled water I used. I also tried some red cabbage juice - which turned a nice blue. I have made soaps for a couple of years but it was not till this year that I seem to be having some kind of Soap fever & I cannot stop making batches of soap - I have 11 dozen batches in my spare room now - and what am I going to do with them? Helppppp!!! and the more I learn - the more I realize different things that can go wrong - but I've never had a lye heavy batch......I had no reason to believe any of the soaps would be lye heavy - I used soapcalc.net, they are olive oil 35%, coconut 25%, shea 20%, Cocoa Butter 8%, Avocado 6%, Castor 6%, with a 33% lye concentration, CP soap, and there were no issues with any of the batches........I do feel reassured that the overall soap could be an irritating substance......and that a lye heavy batch has to be an actual zap - Thanks!


Wellllll.........after reading the way it sounds - its ridiculous. I am an over worrier. and I've gone soap insane. and I wanted ABSOLUTE proof there was not zap.....so when I experienced a teeny tingle after a little while my natural urge was to doubt my soap - and even now I am resisting the urge to sneak and lick of all of the soaps again....omg. my husband has commented there is soap stuff accumulating in the kitchen - I told him I am contributing to science!
Thank you for taking the time to provide some reassurance

Contributing to science 🤣 best answer ever.

Anyway, i need some enlightment too..
I am also not sure how the zap feels like. I tried to do zap test on my liquid soap and experience the same thing it doesnt burn or anything but after a few seconds i can feel tingle and mild burning sensation on my tongue and bitterness.
The ph of my soap is 9.4 so it should be fine i guess??
I dont know how the battery zap feels like and i desperately need an answer..


Sorry if it's not related to CP soap. I was searching for zap test and this threas shows up.


Any help will be very much appreciated
 

Zany_in_CO

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I dont know how the battery zap feels like and i desperately need an answer..
The "zap" of a zap test is unmistakeable. "Tingling", "burning" and "bitterness" are signs that your soap is not done and you should rinse your mouth well and spit. If you are in doubt of whether or not your LS is ready to dilute, you can wait a day or two for it to finish saponifying. Soap has a way of doing its thing whether you help it along or not.

I'm not a fan of the zap test. It's a tool every soaping should have in their toolbox only as needed. Zap testing every batch puts you at risk of compromising your taste buds. I find using phenolphthalein drops to be certainly safer and also the most reliable. Even then, I may have to wait a day or two or three before diluting the soap. ;)

Read what Kenna of Modern Soapmaking has to say about zap testing here (scroll down):

HOW TO pH TEST HANDMADE SOAP
 
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Babyshoes

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The "zap" of a zap test is unmistakeable. "Tingling", "burning" and "bitterness" are signs that your soap is not done and you should rinse your mouth well and spit. If you are in doubt of whether or not your LS is ready to dilute, you can wait a day or two for it to finish saponifying. Soap has a way of doing its thing whether you help it along or not.

I'm not a fan of the zap test. It's a tool every soaping should have in their toolbox only as needed. Zap testing every batch puts you at risk of compromising your taste buds. I find using phenolphthalein drops to be certainly safer and also the most reliable. Even then, I may have to wait a day or two or three before diluting the soap. ;)

Read what Kenna of Modern Soapmaking has to say about zap testing here (scroll down):

HOW TO pH TEST HANDMADE SOAP
Thank you for that article, it was fascinating!
 

Tara_H

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I dont know how the battery zap feels like and i desperately need an answer..
I don't know if this will help but I experienced my first 'zap' last night so will try to help with a description!

I got a tiny bit of the soap batter on a gloved finger, then wet my other fingers and rubbed them together vigorously so it was well mixed together. I just touched the very tip of my tongue to a bit of the liquid and immediately got a very strong sensation, almost like the skin being gently pinched, along with a flavour that I would describe as lemony and metallic.

Trying the exact same thing this morning, none of those things happened, instead it tasted a bit sweet and a bit soapy, and the taste didn't hit for a second or two after I touched it.

I find using phenolphthalein drops to be certainly safer and also the most reliable.
Can you share more about how you use these? I've seen a lot of people recommending them so have been trying to source some, but when I read more into it (including that document you linked) it seems that it will show as pink for anything over about 8. Do you wait for it to stop being pink to count the soap as done?
 
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Zany_in_CO

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Can you share more about how you use these? I've seen a lot of people recommending them so have been trying to source some, but when I read more into it (including that document you linked) it seems that it will show as pink for anything over about 8. Do you wait for it to stop being pink to count the soap as done?
With normal LS the paste normally tests clear at the end of the cook. If not, keep cooking or just cover it and wait for a day or 2 or 3 to finish saponification. In the case of Carrie Petersen's GLS, (forward to the 5:00 marker) the batch tests fuscia right after becoming soap. Wait an hour and the soap tests clear. Read more here:

PHENOLPHTHALEIN USE IN LS
 
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