pH/safety of soaps/lye

Hi everyone,

I'm new to soapmaking and am starting out by researching and reading lots of books before I actually make soap.

My question from my reading is are there cases where certain areas of soap can be lye-heavy and other parts are not. (Top vs. bottom vs. center vs. sides)I heard of lye pockets and certain parts of soap being alkaline and others not.

I know you can use phenophthalein to check the pH of the soap but if I put this in the center of the soap and it comes out neutral, do I have to check other parts of the soap as well or is the lye evenly distributed? What about the issue of lye pockets, how would you differentiate if a liquid pocket of lye was an essential oil or fragrance oil or the actual lye pocket? Would a pH meter be a better tell-all? I know pH papers are not very accurate and I don't want to zap my tongue, don't find it very sanitary if I plan to sell them as well.

My main concern is the safety of using the soaps because I do plan on eventually selling them.

Any answers to my questions are much appreciated.

I've heard that if you use phenophthalein to test on soap that you need to throw out the soap it has contacted because of the possibililty it is a carcinogenic. Now I'm not sure this is true. I read it on a website when I was reading up on making liquid soap. Hopefully, someone who's more knowledgeable will come along and correct me if I'm wrong. I'd say you'd be better off using a pH meter but this is just my opinion.

I've noticed a difference in texture when I've had problems with insufficient mixing and the bottoms of soaps being lye heavy. That's the first thing that I notice when I've unmolded a loaf. It looks wrong. Then I test it and sure enough, it's zapping.

You might want to check out the troubleshooting info on Kathy Miller's site if you haven't already seen it. I've found it very helpful.

http://www.millersoap.com/trouble.html

I do a lot of Hot Process Soap mostly but do some cold- I'm a big user of Phenolpthalein.

It is a carcinogenic so any soap tested- should be cut off of a bar or taken out of the pot if doing HP and tested with gloved hands then discarded when you are done.

I know some people mix a Phenol solution but I do not- it works just the same for me.
You put a drop on a soap sample (preferably taken on the inside of the soap) and if it's screaming Fuchsia you have an issue if the soap is older. Sometimes it will register a light pink which could mean the soap is still saponifying. If you are sure your soap is done and it still goes pink- that isn't good and you should probably rebatch. Phenol tests generally should be done after a 4 week cure for CP anyway.

Hazel- though is right- soap that is wrong- generally looks wrong. You have to really take a good look at all the soap in the batch when you cut it and go from there.
The more you make soap- the more you will see things that could be wrong in your soap. It gets easier to tell the more batches you do. Sometimes it is obvious and sometimes it is not- I have seen lye pockets that are the size of pin points so sometimes it can be hard to tell. When in doubt I test it.

Thanks for the replies.

When speaking of the soap sample, is the soap sample reflective of the entire batch. Meaning if the phenol turns transparent on the sample, this would apply to the rest of the batch? What if it was unwittingly mixed improperly? Since phenol is a carcinogenic I can't test the whole batch with CP, so that's why I'm asking this question.

Also with the sample, I would just use the phenol in the center or if there were lye pockets in other areas, would the phenol only turn fuchsia in certain areas? Meaning would I need to test spot all areas of the soap. That sounds a bit tedious so I'm hoping to get this clarified.

Thanks for the responses.

I never considered using phenolphthalein, since my internet search about soap and indicators told me the following:

- soap has a pH around 9.5-10.5
- phenolphthalein as a pH indicator, has an usage range between 8.2-10

My conclusion was that phenol will give you false positives (some places will turn pink that aren't truly lye heavy). Also, I suspect that phenolphthalein will turn fuchsia when applied to soap ash.

But I guess false positives are better than false negatives ...

Fragola said:

I never considered using phenolphthalein, since my internet search about soap and indicators told me the following:

- soap has a pH around 9.5-10.5
- phenolphthalein as a pH indicator, has an usage range between 8.2-10

My conclusion was that phenol will give you false positives (some places will turn pink that aren't truly lye heavy). Also, I suspect that phenolphthalein will turn fuchsia when applied to soap ash.

But I guess false positives are better than false negatives ...

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I probably should have clarified- light pink in CP soap is ok- it generally goes clear when the soap cures. HP soap- the solution is clear after the cook. When using it- your looking for screaming deep fushcia and there is your indicator of the PH being over 10 more than likely due to lye. Free alkali will always indicate using Phenol.

I also got the same results testing the soap in a solution and using it on a slice of soap.

This is a hotly debated issue on soap forums as to how useful it is- I have been using it for quite some time and it is a useful tool. Perhaps not as useful as an PH meter but not everyone can afford those. I just choose to err on the side of caution and for a few bucks a bottle it's no big deal to do it.

Obviously, Phenol isn't going to give you a number it will give you a ball park. At a PH of 10.5- the solution should be light pink, the lower your PH goes the lighter the color until the lye is used up.
We all know the PH of lye soap, though I don't have a meter, I'm pretty sure that all the soap I have downstairs CP and HP is not under 8.2 and they all have tested clear. So obviously, Phenol isn't really going to indicate at a ph of probably 9-9.5 or so.

I have been caught on a batch of HP thinking it was done- it looked like it- but it wasn't and the Phenol told me to keep cooking. Sometimes you can't go off sight though it's a lot easier to do so with CP soap.

I test my end slices or any soap that looks suspicious.

Here is a good article and in the comments it talks about pink soap:
http://summerbeemeadow.com/content/phen ... h-and-soap

Phenol is going to indicate on the higher end of the PH spectrum than the lower. Excess lye in your soap will give you a very high ph especially if you have been curing the soap for a month or so. Generally, with those batches you will see something wrong.

Phenol isn't the end all be all and certainly isn't necessary and not everyone believes in using it but it does come in handy. It's awesome for Cream Soap as well.
To my knowledge- I haven't had any false readings either. I have tested unsapped soap just to see what it does. It's interesting doing it during an HP cook.

As far as ash goes, I haven't had any in awhile but I suppose it would test fuchsia unless the lye is diluted as it hits the air turning into sodium carbonate. I'll test it and report back next time I see some which is hopefully not to soon but you never know.

daisy211 said:

Thanks for the replies.

When speaking of the soap sample, is the soap sample reflective of the entire batch. Meaning if the phenol turns transparent on the sample, this would apply to the rest of the batch? What if it was unwittingly mixed improperly? Since phenol is a carcinogenic I can't test the whole batch with CP, so that's why I'm asking this question.

Also with the sample, I would just use the phenol in the center or if there were lye pockets in other areas, would the phenol only turn fuchsia in certain areas? Meaning would I need to test spot all areas of the soap. That sounds a bit tedious so I'm hoping to get this clarified.

Thanks for the responses.

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Can someone please answer this part of my question? Thank you. I just don't want to be discouraged from making soap because of my concerns relating to safety of usage.

My samples are reflective of the entire batch- if you have pockets you will see them. If you have bright white spots- that is another good sign that your improperly mixed.

I usually test the outside of the sample and the inside of the sample and go from there. I don't test every bar of soap. Generally, IMO, if you have a lye heavy batch you will have the Phenol register. I have taken a sample of an end that looked normal but when I cut there was a pocket and the sample was still really purple.

If your soap was improperly mixed you will see that way before you even need to use the Phenol. You should wait the full 4 weeks to test the soap if it's CP.

If you have an area of the soap that is concerning you, test that part too.

Generally if you have taken your soap to a pretty good trace, you should be fine as long as you measured accurately.
Soap with excess lye will be very drying to the skin as well- sometimes it can sting and other times make your hands feel slippery and weird. So watch out for that as well.

I wouldn't be discouraged from making soap- some batches will bomb either way but once you are used to the process- you will know exactly what to look for and if your batch is wrong.
Hang in there...I hope this answered your question.

I'm pretty sure that all the soap I have downstairs CP and HP is not under 8.2 and they all have tested clear. So obviously, Phenol isn't really going to indicate at a ph of probably 9-9.5 or so.

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This means we are missing something here.

Have you tried with a water solution (put some shavings of soap in a small glass of water and add few drops of phenol) ? Maybe soap gets very dry and it doesn't mix properly.

Check the picture at this link:
http://www.chempage.de/lexi/phenolphthalein.htm

Phenol should show pink starting with pH 8, I remember trying a baking soda water solution (which is less alkaline than soap - pH about 8.3), or you can try borax - pH little over 9.

Your link is broken, btw.

Also, I've started looking into using red cabbage as an indicator. In theory, it should show the color difference better than phenolphtalein, and is also not carcinogenic (quite the opposite).

Also, I've started looking into using red cabbage as an indicator. In theory, it should show the color difference better than phenolphtalein, and is also not carcinogenic (quite the opposite).

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I've been using red cabbage as an indicator and it's pretty good at showing when the saponification process is complete. Any yellow or green indicates that lye is still present. When the strips are dark aqua/blue color without changing to yellow, it's good to go. At that point I usually do the tongue test to double check. You can get a lot of mileage out of one cabbage. Plus, it's economical, and definitely not carcinogenic. :wink:

Can someone please answer this part of my question?

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Wisely chosen samples will be reflective of the batch.

It can be good idea to choose more than 1 sample: from the top, the bottom, the middle and the sides or other suspect areas.

Also, if your oils are fully melted and the lye is completely dissolved, I cannot imagine how you could improperly mix, unless done on purpose.

If you cut your soap into slices and see that the whole surface of all slices looks smooth and nice, it means it's been properly mixed and it hasn't separated.

Soap with excess lye will be very drying to the skin as well- sometimes it can sting and other times make your hands feel slippery and weird. So watch out for that as well

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Is this the worst that can happen with lye-heavy soap? Can you possibly burn your skin or blind your eyes with lye-heavy soap that's hardened and cooled? Or is that only with the lye solution?

Also what size sample do you need to cut? Can it be a tiny sliver or does it need to be more like a bigger bar?

why not just zap test? i have never used phenolphtalein or any other test strips. it seems to me that if you are likely to get false positives and have to throw away parts of your soap, then why not just zap test and and know for sure? it is cheaper, easier and you will know instantly and for sure if your batch is not right.

Can you possibly burn your skin or blind your eyes with lye-heavy soap that's hardened and cooled?

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Depends how heavy it is on lye ... But like I said, if you're careful, I don't think it's possible to have such a lye heavy soap and not know about it.

Worst that I heard is eye burns and stinging sensation / redness to the skin.

About eyes, you shouldn't put even good soap into your eyes, because it's irritating.

Is it okay if the sample I cut for phenol is really small, or can that affect how it reads? I just don't want to waste a lot of my soap for readings!

It's ok, but I wouldn't go below the size of your pinkie's fingernail, also don't cut it thin enough to be transparent - I imagine that would make difficult to see the color.