# Phenolphthalein Use in LS



## Zany_in_CO (Nov 30, 2019)

From my Files - This is a quote from Steve Mushynsky, Owner of  www.summerbeemeadow.com and long-time member of the Liquid Soaping Yahoo Group which is soon to be Defunct. He explains why Pheno drops or, as he says, "Phenol P", works as an indicator for excess lye in LS. I quote his post in its entirety here for those interested in using Phenolphthalein to test their paste before dilution.

HTH 

_Phenolphthalein is an indicator that changes color at a very specific  range of pH levels that happens to be perfectly suited for liquid  soapmaking. There is actually no difference between having 'excess lye  in your soap' and your soap having too high a pH level as 'excess lye'  would create a high pH level and having too high a pH in soap would be  caused by 'excess lye'._

_A very simple pH meter can cost $35 and up and requires purchase and  use  of standard pH solutions (cost for a set around $25) for recalibration  each time the meter is used to be accurate.  I can't discount the  usefulness of having accurate pH readouts as I used one during a series   of test batch pH evaluations that I did a while ago. It is, however, a  bit of a bother to recalibrate the meter each time, and skipping this  can result in the meter reading way off from being accurate._

_On the other hand, using Phenol P correctly will give an easy, reliable   result. Basically. if the test solution is clear or just ever so  slightly pinkish, the soap's pH is 9.5 or less.  If the test solution  is  distinctly pink or red when a drop of Phenol P is added, then the soap  test solution is higher than 9.5 pH and can be brought down a bit with  a  weak borax solution addition.  It's an easy simple way to test for  acceptable pH level in LS._

_As to what pH you'd want your liquid soap to be, I found that levels of   9.5 to 9.3 at the lowest are generally ideal for liquid soaps  containing  some coconut and some oleic-containing 'soft' oils also.  Any less than   this and they are very prone to clouding due to too low pH or upon  addition of fragrance. This was after doing a lot of test batches, each   measured laboriously with a recalibrated meter.  Inasmuch as this 9.5  to  9.3 range is exactly the range where Phenol P works, I no longer use a  meter for any production batches.  Phenol P works just fine instead._

_By the way, different oils produce different liquid soaps that can  tolerate different pH levels.  Olive oil liquid soap can cloud if  brought to below 9.5 pH, whereas pure coconut or castor liquid soap can  be brought to around 8.5 ph without clouding. This means that while  coconut based soap is generally considered to be a bit harsh, it's  ability to be made at a lower pH can counteract this, as lower pH's are   themselves less harsh to the skin. If one were to push a high-coconut  or  castor soap toward an 8.5 pH level, one would then want to use a meter,   as this is below Phenol P's useful range.  Unfortunately, such soaps  produce an undesirably water-thin resulting product, so it wouldn't  come  up often._


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## Monmarstan (Dec 16, 2019)

Thank you for this, but as a new soaper, this is what is confusing... I bought some phenolphthalein and in the directions, it says that it will turn pink once the product passes a pH of 8. If real liquid soap (technically and typically) has a pH of ~8.5 to 10.1, how is this phenol stuff helpful? I JUST found out there are different kinds of phenol (ethanol vs propylene glycol-based. So, which one is the correct kind? Does it matter? I found one on Amazon that will remain colorless  under a pH of 8.2; then turn purple from 8.2 - 12; then turn colorless again over 13. I guess my question is, if real soap is supposed to be alkaline at a pH of over 8, what, exactly, is the point of this stuff? I'm sure I must be missing something that will bring clarity to this whole issue, so if you don't mind, please help! I'm SO confused.


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## Zany_in_CO (Dec 16, 2019)

I use the phenolphthalein solution, 1% in ethanol, from *Duda Diesel *
Its purpose is to make certain there is no excess lye in the paste, i.e., the soap is fully saponified, before dilution. If the drops turn bright pink, you must wait until the drops test clear. In some cases, that may be a few days after making the soap.

In the case of subbing glycerin for the water to make the lye solution, where it takes all of 2 minutes to become soap, it tests bright fuscia after the cook. Wait 1 hour, and it tests clear.

HTH


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## DeeAnna (Dec 17, 2019)

Phenolphthalein is a pH indicator. Just as a pH meter is just a pH meter. Both are measures of pH. They do NOT do anything more than that. Phenolphthalein (or a pH meter) used alone is not, _not_, *NOT *a test for excess alkali (lye).

No matter what people in the soapmaking community say ... whether it is Zany, Catherine Failor, Steve from Summerbee, or anyone else ... the use of phenolphthalein alone (or a pH meter alone) is categorically not a useful and accurate test for excess alkali (lye).

Phenolphthalein (or a pH meter) can be used as a pH indicator _as part of_ a useful and accurate test for excess alkali, but just dripping phenolphthalein in diluted soap or on bar or paste soap and observing the color (or testing pH with a meter) is NOT the same thing as this test.

The excess alkali content _cannot _be determined simply by measuring pH alone.

I will not get into this discussion yet again with Zany. I will not listen to her trot out all the "sources" she has from within the soap making community who purport to "know" that phenolphthalein does what they say it does.

Suffice to say for others who are reading this thread ... phenolphthalein has legitimate uses as a pH indicator, but it is a pH indicator only. That's it. It doesn't tell you squat about anything else.

And for phenolphthalein to be used correctly as a pH indicator, the soap solution it is used in also has to be prepared correctly. You don't just drop phenolphthalein indicator solution on a bar of soap or on some soap paste. And soap solution that has been diluted for use is not sufficiently diluted for testing pH.


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## Monmarstan (Dec 17, 2019)

Thank you both for taking the time to share your views with me! I'm going to forgo using phenolphthalein ... at least until I know A LOT more about soapmaking!


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## IrishLass (Dec 19, 2019)

Ditto 100% all that DeeAnna said. 

The below comment by Steve Mushynsky that Zany quoted is very misleading:

_"There is actually no difference between having 'excess lye in your soap' and your soap having too high a pH level as 'excess lye' would create a high pH level and having too high a pH in soap would be caused by 'excess lye"._

If I could question Mr. Mushynsky, I would ask him what he considered to be too high of a pH in soap? Would it be 10? Would it be 11? Would it be 12? How about 12.4? I would pose these questions because Johnson & Johnson makes a baby oatmeal soap  (a real lye soap, i.e., not a syndet) with a documented pH of 12.4. I'm sure many of us would consider a pH of 12.4 in their soap to be pretty high, and going by Mr. Mushynsky's opinion, most likely lye heavy, too.....but guess what? There is no lye excess in the J&J  baby soap, and this soap actually rated the least in skin irritability on the Irritability Index Scale in comparison to other soaps with a lower pH..... The soap with the highest irritabilty was a Camay soap with a pH of of 10.4

At the risk of sounding like a broken record for as often as we have had to repeat it, _pH and excess lye are two different things_. You _cannot_ confirm (or assume) excess lye in soap via a pH reading!


IrishLass


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## Carl (Dec 19, 2019)

IrishLass said:


> Ditto 100% all that DeeAnna said.
> 
> The below comment by Steve Mushynsky that Zany quoted is very misleading:
> 
> ...



That's a really tough statement to analyze (the one that you quoted).  It's almost like there's an assumption there that a high PH is harmful, which is not the case.  The author seems to assume that anything with a PH over 9.5 is harmful.  Check out this link (https://courses.lumenlearning.com/wmopen-nmbiology1/chapter/the-ph-scale/)  It has soapy water on the chart and lists it as 12.

I would like to think of "Excess Lye" as the lye that was not used in the saponification process.  So let's say I have a 0% superfat  recipe that calls for 20 grams of lye and I put in 40 grams mistakenly , then I have 20 grams of lye that were not used up by the chemical reaction, thus "Excess Lye."  This could and should have a high PH.  But good soap should also have a high PH.  So how can you tell the difference?  I guess you can't using PH.


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## Zany_in_CO (Dec 19, 2019)

IrishLass said:


> _pH and excess lye are two different things_. You _cannot_ confirm (or assume) excess lye in soap via a pH reading!


I agree. Just to be clear, I am not using the drops to get "a pH reading!  In a previous post I mentioned that I use Phenol drops to test the paste "for excess lye" before moving on to the Dilution Phase. In that case, and upon further research in reponse to your post, the drops serve as an "acid base indicator". IME and IMHO, it is the most reliable option. On behalf of all the LS-ers who do the same, I offer this explanation and demonstration:

Source: _*https://www.sciencecompany.com/Phenolphthalein-30ml-1-oz-P6364.aspx*_

PHENOLPHTHALEIN pH Indicator, 1 oz.  - 1% in Ethanol.

*What is an acid-base indicator? *(Quote in Blue)
_An acid-base indicator is a weak acid or a weak base. Indicators have a very useful property - they change color depending on the pH of the solution they are in. This color change is not at a fixed pH, but rather, it occurs gradually over a range of pH values. This range is termed the color change interval. Each pH indicator is defined by a useful pH range. *For example Phenolphthalein changes from colorless at 8.2 to pink at 10. *_

Demonstration of how it works:
_*
*_
HTH_* *_



Carl said:


> I would like to think of "Excess Lye" as the lye that was not used in the saponification process.


Exactly. 



Go to the 5-minute mark to see how Carrie uses Phenol drops to test for excess lye. The drops turn bright fuscia at the end of the cook. After an hour the paste has fully saponified and the drops test clear. Pretty cool, actually.


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## gloopygloop (Dec 20, 2019)

But surely, Zany and I may be wrong here but in the post regarding "Carrie using phenol and it changing colour  just 5 minutes into the process it is because the paste had not yet fully saponified and a tongue zap test which is what I have always used would have proved positive also with a zing, after the paste had sat for a while it would then have fully saponified or cured just as CP or any soap does whereby it had used up all of the lye and a second tongue test would have given no zing.


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## Zany_in_CO (Dec 20, 2019)

gloopygloop said:


> a tongue zap test which is what I have always used would have proved positive also with a zing, after the paste had sat for a while it would then have fully saponified or cured just as CP or any soap does whereby it had used up all of the lye and a second tongue test would have given no zing.


Correct.


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## DeeAnna (Dec 20, 2019)

_"...use Phenol drops to test the paste "for excess lye"..."_

For everyone besides Zany, the real fact is this -- using phenolphthalein is not a valid test for excess lye.

One of the reasons why this is not a test for excess lye is that when you cook the snot out of a soap paste, there's not enough free water for pH to be a measurable property. There is so little water left that hydrogen ions -- the chemical that is measured by a pH test -- cannot exist in free ionic form. This lack of free water is why phenolphthalein doesn't turn pink. 

To get an accurate pH for soap, the test must be done on a mixture of water containing only 1% to 10% pure soap. Only then can the hydrogen ion concentration -- the pH in other words -- exist as a property that can be accurately measured.

Even if you do the pH test properly, you _still _do not know whether the pH is the normal pH for a no-free-alkali soap or if the pH also indicates the presence of free alkali (aka excess lye). There is a test that will tell you the free alkali content in a soap, and yes the test can include the use of phenolphthalein, but it's not just about dripping phenolphthalein on or in soap.

***

_"...use Phenol drops..."_

I've also warned about this before, and this point is also not sticking.

So again for everyone else -- Phenolphthalein is not  _phenol_. It's _phenolphthalein_. Shorten it to _phenol-p_ or _pheno _if you must.

But do not shorthand this word to phenol with an "L" at the end. Never give anyone the slightest reason to think they need to have actual, real phenol in their possession. Phenol is a deadly poison.


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## gloopygloop (Dec 20, 2019)

DeeAnna said:


> _"...use Phenol drops to test the paste "for excess lye"..."_
> 
> For everyone besides Zany, the real fact is this -- using phenolphthalein is not a valid test for excess lye.
> 
> ...



Makes sense to me, pH.....( potential Hydrogen I believe ?) Never felt tempted to go the phenol route, my tongue lets me know.


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## DeeAnna (Dec 20, 2019)

Good point, @gloopygloop. Just as a wetted finger can tell me the direction of the slightest breeze, the zap test can tell me whether there is the tiniest bit of excess alkali or not. 

Sometimes empirical tests are accurate enough for the purpose. I don't always need an anemometer to tell me the exact wind speed and direction, nor do I necessarily need to do a test for free alkali.


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## linne1gi (Dec 21, 2019)

DeeAnna said:


> _"...use Phenol drops to test the paste "for excess lye"..."_
> 
> For everyone besides Zany, the real fact is this -- using phenolphthalein is not a valid test for excess lye.
> 
> ...


I so agree, plus phenolphtalein drops are basically a pink color from pH 8.2 - 14.  So it really isn't possible to tell if the soap is a reasonable pH.


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## Zany_in_CO (Jan 5, 2021)

linne1gi said:


> I so agree, plus phenolphtalein drops are basically a pink color from pH 8.2 - 14.  So it really isn't possible to tell if the soap is a reasonable pH.


Um, not exactly correct *@linne1gi*. See post #8, quote in blue from the manufacturer... phenolphtalein drops are colorless at pH 8.2 and turn pink at pH10. That's what makes them so very convenient and reliable of all the options available for testing LS paste before moving on to the Dilution Phase.


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## linne1gi (Jan 5, 2021)

Zany_in_CO said:


> Um, not exactly correct *@linne1gi*. See post #8, quote in blue from the manufacturer... phenolphtalein drops are colorless at pH 8.2 and turn pink at pH10. That's what makes them so very convenient and reliable of all the options available for testing LS paste before moving on to the Dilution Phase.


This article explains that phenolphtalein drops turn pink at pH 8.3 and stay pink up to and including pH 14.








						How to pH Test Soap the Right Way & Why It Matters!
					

Curious about how to pH test handmade soap properly, regardless of whether it's bar soap or liquid soap? Here's the lowdown on pH testing soap, and why you should (or shouldn't!) care.




					www.modernsoapmaking.com


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## DeeAnna (Jan 5, 2021)

linne1gi said:


> ...phenolphtalein drops *turn pink at pH 8.3*....



Yep, that's correct. Here's the right stuff --

Phenol-p is normally colorless if the pH is below about 8.2. (It can turn deep orange in extremely acidic solutions.)

Phenol-p will be a light to medium pink from a pH of 8.3 up to 10. *This change from colorless just below 8.3 to pink at 8.3 is what most people are interested in when phenol-p is used as a pH indicator.*

At pH 10 to 13, Phenol-p will be a deep fuschia -- as deeply colored as it can get. I think this might be what Zany's supplier is talking about, although the wording is truly misleading. At the higher end of this pH range, the color may slowly fade over time to colorless.

Phenol-p is colorless above a pH of about 13.









						Phenolphthalein - Wikipedia
					






					en.wikipedia.org
				











						Phenolphthalein
					

Phenolphthalein | C20H14O4 | CID 4764 - structure, chemical names, physical and chemical properties, classification, patents, literature, biological activities, safety/hazards/toxicity information, supplier lists, and more.




					pubchem.ncbi.nlm.nih.gov


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## linne1gi (Jan 5, 2021)

DeeAnna said:


> Yep, that's correct. Here's the right stuff --
> 
> Phenol-p is normally colorless if the pH is below about 8.2. (It can turn deep orange in extremely acidic solutions.)
> 
> ...


From what I remember, it is pretty hard to determine what color pink you are looking at. It’s just a deeper pink. I honestly don’t believe you can have a soap that has a pH below 8.2.  It just wouldn’t be soap at that point.  And I don’t remember the phenolphthalein going colorless. Of course it has been a long time since I graduated from college (about 47 years) lol.


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## lsg (Jan 5, 2021)

I put a drop of phenolphthalein liquid on a bit of my glycerin liquid soap paste.  If it turns pink, I wait for a few days and try it again.  This has worked well for me.


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## DeeAnna (Jan 5, 2021)

linne1gi said:


> From what I remember, it is pretty hard to determine what color pink you are looking at. It’s just a deeper pink. I honestly don’t believe you can have a soap that has a pH below 8.2.  It just wouldn’t be soap at that point.  And I don’t remember the phenolphthalein going colorless. Of course it has been a long time since I graduated from college (about 47 years) lol.



People claim to be able to see differences in the shade of pink and know the pH, but, yeah, I'm not a true believer either. No chemist worth their pocket protector would think that's a valid idea. So you're in good company!

And, yes, I agree that any soap that really has a true pH of 8.2 is no longer soap -- it's mostly fatty acids. I've been working for awhile on an article about this topic, and got it uploaded to my website a few days ago -- Soap pH | Soapy Stuff

The thing about testing pH is that it has to be done in a dilute solution to get accurate, repeatable answers. If you try to test soap that is too concentrated, the "pH" reading you get is artificially lower than it truly is. Essentially the pH reading is affected by the lack of water because the soap molecules are not free to fully ionize.

Some people, for example, cook their liquid soap paste for hours 'n hours and keep testing it by dropping phenol-p onto a dab of paste until the phenol-p remains colorless. Then and only then is the soap supposedly saponified.

What's really happening is they're cooking so much water out of the paste that the OH- ion concentration (the ions that contribute to a high pH) is artificially very low. If the OH- ion concentration is artificially low, the pH will appear to be considerably lower than it really is.

If this paste would be diluted to a 1% to 10% pure soap content, phenol-p should turn the soap mixture pink just as you'd normally expect. Cooking soap to death doesn't change the essential nature of the soap -- it still remains alkaline (in the 9-11 range), just like soap should be -- but ya gotta do the pH test correctly.


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## violets2217 (Jan 5, 2021)

DeeAnna said:


> No chemist worth their pocket protector


I wanna be a chemist now, just to earn my pocket protector!  Thanks for the Soap pH link! Heading to read it now!


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## linne1gi (Jan 5, 2021)

DeeAnna said:


> People claim to be able to see differences in the shade of pink and know the pH, but, yeah, I'm not a true believer either. No chemist worth their pocket protector would think that's a valid idea. So you're in good company!
> 
> And, yes, I agree that any soap that really has a true pH of 8.2 is no longer soap -- it's mostly fatty acids. I've been working for awhile on an article about this topic, and got it uploaded to my website a few days ago -- Soap pH | Soapy Stuff
> 
> ...


Yes! Exactly. I come across so many people who tell me their soap has a pH of 6. That with careful maneuvering of contents they have been able to get their pH to that level. There is nothing to even say, because they don’t believe me.  I’m pretty sure Dr Kevin Dunn is still willing to test someone’s soap that has a pH of 6. SMH!


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