In cold process, how long does it take for chemical reaction to occur?

[Saltynuts]

I think in hot soap making, the chemical reaction is basically supposed to be done before you stop the cooking process.

But in cold soap making, I think even after the soap dries the chemical reactions making it soap are still going on. How long after you mix it up before the chemical reactions are completed? I know you want to have a "cure period" of a few weeks, but I think that is different, I think the chemical reactions are done after 2 or 3 days maybe? Can you do the "zap test" on a bar of soap sitting there to tell you if the chemical reactions are complete?

Thanks!!!

 

[Obsidian]

The chemical reaction you are thinking of is saponification and yes, 2 to 3 days really should be the max it takes to complete.
You can zap test to see if there is any lye still active but I wouldn't recommend it, if the soap was still highly caustic, you could get a chemical burn.
Wait at least a week to zap test, that will give it plenty of time to complete the process.

Curing is different but there is still a chemical reaction going on. Due to this, all soap needs a proper cure regardless if its HP or CP.

 

[ResolvableOwl]

Depends on the recipe. A 100% CO laundry bar might be finished reacting after a few hours, but an old-fashioned castile might need a week or longer.

Then I'm wondering about the XY question: what might be your reason to ask. Using soap earlier than 2 weeks into cure is disappointing anyway. In case you'd like to know if you need gloves to work with the bars (like handling during cutting, planing etc.), they have other uses besides protection from chemical burns. They prevent fingerprints, leave the hands clean (e. g. from leaking FOs), and are part of good manufacturing practice.

 

[Saltynuts]

Thank you Obsidian and Owl! Owl, I was just mostly curious I guess, but I was just thinking its best if I handle it not at all before the cure period since I assume if I touch it it could cause chemical burns and what not.

I will say this - I put some CP soap I made to my tongue like 24 hours (maybe even less) after I made it, and not zap/shock at all. So it seems like the reactions might actually be done in less than 24 hours.

 

[ResolvableOwl]

No more zap is pretty much the definition of “saponification has ended” (at least in layman's terms without fancy lab equipment).
I hope you didn't touch the bar with your tongue directly? That's not how the zap test works.

 

[Saltynuts]

Thanks resolvableOwl! So I just broke off a small piece of the soap and put it on my tongue - that works for the test correct? Yea I was not going to put my tongue right on the bar of soap, memories of the kid getting his tongue stuck to the freezing pole in A Christmas Story were coming back to me.

Thanks!

 

[The Efficacious Gentleman]

While I respect where obsidian is coming from on the zap test, staging the zap test is the sensible option if testing within the first week - wet your finger and rub it on the soap, wait for a bit and see if it tingles. If not, gentle dab the soapy finger on your tongue, by a sink with water on hand - any tingling you can rinse immediately. If it doesn't tingle, you can try a bar on the tongue (again at the sink for the same reasons). I also would not just french kiss a bar of soap without doing the first two steps for my own peace of mind

ETA - I see owl posted a link to irishlass describing a similar process!

 

[Saltynuts]

Thank you all!!!