Sunday, February 22, 2015

Kevin Dunn has an interesting challenge for all you liquid soap makers!

As you all know I don't make handmade soap, but I buy it and I'm fascinated by the chemistry of it. After a lengthy discussion that happened in this post, I wrote to Kevin Dunn of Scientific Soapmaking to ask him a question, and he responded!

Kevin Dunn has put forth this challenge. (To learn more, click here!) "In the Sep/Oct 2014 issue of the Saponifier.com, I discussed the prospect of lowering the pH of liquid soap to pH 7. I remain skeptical that such a thing can be done, but claims to the contrary persist. So I am issuing a friendly challenge to the handcrafted soap community. Send me an 8 oz bottle of your pH 7 liquid soap."

He goes on to specify what the soap must consist of and the awesome way he will be testing the results. If you have brought your soap down to pH 7 AND your soap doesn't contain anything other than water, soap, glycerin, any combination of fatty acids, and citric acid or vinegar, you can send your results to him. I'm dying to see what happens!

I can't encourage you enough to read his page. He explains the chemistry of soap making in such an interesting way!

The soaps above are from Corry. I don't have a link for her page yet! If you're reading this, please send me an email! 

27 comments:

Jennifer said...

Hi Susan, I too did the research and thought it was not possible...but then I read something from a chemist that had me rethinking the whole subject. He talked about Ph vs PKa, and how a fatty acid could reduce the pHone of the soap without causing the soap molecules to precipitate. I can't wait to hear the results of your challenge! Inquiring minds definitely are dying to know!

Susan Barclay-Nichols said...

Hi Jennifer. Can you send me that information or link to it somewhere? I can't find anything on this topic, and my discussion with Kevin Dunn confirms that it isn't going to reduce the pH by any meaningful amount. I'm curious to see what this other person says!

And it's not my challenge. It's Kevin Dunn's challenge.

jennifer said...

http://www.newton.dep.anl.gov/askasci/chem99/chem99655.htm

This is the place I started with.... I am not a chemist myself so I cannot dispute his response about pKa of fatty acids moving the pH of soap!

Kevin Dunn said...

jennifer said...
http://www.newton.dep.anl.gov/askasci/chem99/chem99655.htm

This chemist gives a correct explanation of the chemistry, but he does not give the pKa values for the fatty acids. These are given in Chapter 13 of Scientific Soapmaking. The lowest value is for lauric acid (7.5). Below a pH of 7.5 there will be more lauric acid than sodium laurate (soap). Sodium laurate would be most common one produced from coconut or palm kernel oil.

Barb Miller said...

Following!

Susan Barclay-Nichols said...

I also need to clarify that I might not make soap, but I understand chemistry and the chemistry of soap. I'm growing a bit weary of the argument that not making soap means I don't understand what I've been studying for years.

Kevin Dunn said...

Let's say you have 10 molecules of soap. You add two molecules of a strong acid, which turns two molecules of soap into two molecules of fatty acid. You now have eight molecules of soap and two of fatty acid. The ratio of acid to soap is 2/8 = 0.25. But if you add two molecules of fatty acid to ten molecules of soap, all the soap remains and the ratio of acid to soap is 2/10 = 0.2. Thus, molecule for molecule, the strong acid is going to have a greater impact than the fatty acid. Also fatty acids generally have higher molecular weight than citric acid or acetic acid. So pound for pound, the strong acid will have an even greater affect than the fatty acid. An ounce of fatty acid will lower the pH, but an ounce of citric acid will lower it further.

PracticalSoapmaking said...

Exactly Dr. Dunn. pH is a logarithmic scale, not an average. The calculations also depend on molarity of the products being combined.

Susan Barclay-Nichols said...

Please note that I removed a comment from this post as per the criteria set out here.

B. said...

So still no entries...
B.

Susan Barclay-Nichols said...

Hi B! I find that very curious as I have seen a few soap makers making the claim that they could reduce the pH of their soap and I had thought they'd be dying to prove themselves right! I was really looking forward to the results!

Maria said...

I've certainly tried lowering the pH, however, I didn't get it that low and I did try a lot of different things. I was able to lower it somewhat in a batch that was mostly coconut oil, some castor oil and no superfatting. I used citric acid (careful, careful) and salt. I was actually adding the salt to try and thicken it (it will thicken it some, but honestly. There are easier ways.) After adding a bunch of salt (over the recommended dose) I tried more citric acid and it actually took it without falling out. It *seemed* that the soap accepted more citric acid because of the salt. I'm not a chemist. I was messing with things to see what happened. It was the lowest pH soap I've ever made, but I wouldn't make claims about it as I don't have a very accurate measurement device. All that said, I moved on to making shampoo and it seems to me that if you want a lower pH, it is vastly simpler to just use a surfactant instead. Soap has its pluses, but so does shampoo.

Tarc said...

Hmmm. It should be possible, but challenging, mostly because he limited the large number of safe, typical weak organic acids to those that can barely accomplish the task because of the pKa. Neither acetic acid and citric acid would be a buffer of choice for neutralizing soap IMHO. Phosphate is used nearly ubiquitously in detergent formulations because it's really easy to combine stock solutions of the mono-basic and dibasic phosphates and use just a bit of it to set the pH wherever you like. Phosphate-citrate might work as well. I don't think I'd want to use a soap with enough citric acid (AHA) or acetic acid (smell) to get it to that pH.

Vidyut said...

I haven't specifically tried to lower the ph of soap so far, but I checked a few of the soaps I thought are mild after reading this post, and the lowest ph of them is a hot process with about 40% coconut oil, 30% palmolein, 10% castor oil and 10% kokum butter, superfatted 10% or so with 2% of soap weight worth honey added after the soap was ready and before pouring. It is brown in color (from the early bit of honey turning into caramel). Ph 7.3. Lathers fine.

Does adding honey count? I think some of it charred when I poured a bit too early and stopped and waited. :p

Worth trying this purposely and seeing if I can take it lower to 7 - will dissolving it count as liquid soap?

This is probably going to waste my time chasing my tail for no specific achievement, but.... now the idea is intriguing.

Vidyut said...

Further update. I didn't get time (or that much obsession) to make a soap from scratch, etc. Much happening on personal front. But I had thought that honey had brought the ph of the soap lower in the soap with lowest ph among mine. So, as a proof of concept, I dissolved some soap shavings (this is a mix of various cold process soaps and no detergents or other stuff for foam) in some water and made a thick paste. Diluted that paste with about similar quantity of honey. Measured ph - 6. The "soap" didn't fall apart, but it didn't lather in use either, though the soution in the bowl had nice bubbles. Leaving the cup to sit overnight to see if it needs some time to fall apart (or lather). If it doesn't, may spend some more time and do the same thing, but measure a bit more carefully (I think that was a lot of honey) to see if I can do a ph 6.9 soap that wants to foam as well. If that happens, maybe it is worth it trying to make from scratch and come up with an exact recipe, make video, etc. If it doesn't foam, I don't see the point going through all the effort just because it didn't fall apart.

Vidyut said...

Further note: There are no emulsifiers in the soap, so at ph 6 it hasn't "fallen apart - yet. So at least the part about oil separating out may not be true always. Will update if it holds overnight.

The other problem is that I can't think of a reason to need this soap. High ph soaps are just fine for living skin, unlike dead hair and I can't imagine using a shampoo with so much honey in it. Not sure the result will be worth the effort.

Susan Barclay-Nichols said...

How are you testing your pH? Why wouldn't you send this into the challenge if you've accomplished this low pH soap?

Vidyut G K said...

Susan, it doesn't lather much (almost not at all). Also I've made it from cold process soap shavings - no way I can give the recipe for it - whatever mixed soap shavings were there. And of course I don't have a video. Son was hospitalized to fix a hip dislocation. Things crazy here. Maybe will do it properly. I don't see the point of a soap that won't lather, even if ph is under 7.

Vidyut said...

I used the strips to test ph. But if I eventually make something even willing to lather lightly, can test with meter as well. I have both.

Vidyut said...

Susan, my thing isn't so much to make claims about accomplishing a ph (hadn't even thought to do it till reading this post). I don't have any such claim. I am just intrigued by the challenge and playing. What I made isn't a soap I'd want to use (haven't tried to improve on last update yet). If I can make a soap I'd want to use, I'll definitely make the effort of having a proper recipe and process and making the video and all. Otherwise what to submit to the challenge? A solution of soap shavings mixed with honey vaguely 1:1 - what density of solution? Unclear. What ingredients of soap? Random mix of usual recipes. Probably coconut high recipes. Not awfully scientific to attach my name to a claim :p

Right now I'm just finding out for myself and sharing if anyone else is interested. Maybe it isn't even soap and has fallen apart, only in a way that holds together as a solution. Sure doesn't lather like soap.

Vidyut said...

Update: Made a shampoo bar of cold process soap. Oils used Coconut (40%) + Rice bran (25%) + Sunflower (20%) + Castor (10%) + Cetyl Alcohol (5%). Water phase (these are % of total oil weight, though not part of it, of course) had EDTA in lye water (0.5%) and Honey 4%, Panthenol (3%), citric acid (1%) in some more filtered water after trace. 50% of the lye liquid was milk. Liquid weight was 2.5x that of sodium hydroxide weight by calculating a 5% lye discount.

Two days after making, dissolved a crumb in filtered water. Used meter to check the solution - Ph 7. Don't have distilled water at home. Not sure if worth the effort to go out and buy some just to test what appears to be an achieved ph unless my new meter is faulty (doesn't seem so), but if the challenge will accept my soap and needs that, I can do it.

Checked out Kevin Dunn's challenge again. Can send him the soap (bar, not liquid), but he hasn't listed citric acid or honey as among the neutralizing agents. Only fatty acids. Not sure my soap qualifies.

The Ph is definitely 7 using a meter (6.8 on strip swiped on wet soap - was surprised to know it wasn't same). Don't know how to post photo here, so tweeted photo of meter reading - though frankly, it is hardly proof - could be anything I dipped it into and clicked photo. But I believe the recipe should be reproducible. Didn't do anything fancy. Standard cold process stuff.

Melted cetyl alcohol, mixed with liquid oils (coconut oil is liquid here), put in the lye solution (in 50-50 milk and water), brought it to trace, added the DL-Panthenol, citric acid and honey mixed in some water, brought it to trace again (it wanted to fall apart, so took some mixing before it traced properly again. Added essential oils (Holy Basil and lemon), mixed thoroughly once more till thick trace (was worried about separation issues), poured into mold, done. Unmolded and cut a day later, another day later, tested ph. https://twitter.com/Vidyut/status/704622324532715520

Should be reproducible. Did pretty much nothing else to it. Used madder root powder to color an accent, but both colors of soap test same Ph.

Vidyut G K said...

Oh. I'd tossed in a silkworm cocoon into the mixed lye. I don't think that is relevant to ph.

Susan Barclay-Nichols said...

I think you should send it in to him. So many people have claimed they can do it, but no one enters the challenge. How much would it cost you to send it in versus enjoying the process of seeing the analysis that will happen with the soap? I think it's so worth it!

I feel so strongly about this, that I will send you some money to pay for postage. I want someone to enter this challenge and see the results!!!

Vidyut said...

Hahaha. No need to send money. I'll send the soap to him. You got me at "analysis" :D

I am intrigued too. Just that it seemed like I used methods beyond what he was looking for. Regardless, even if it doesn't win the challenge, will be interesting to see what he has to say about it.

Though I don't know what I did that is so different from so many people who claim to do it other than using honey and milk. Didn't seem all that difficult either for a first attempt. Perhaps they aren't telling tall tales either. Now that some time has passed, who knows, maybe the Ph dropped further :p Should test that too :D

My gut feel from this is that it is more difficult to achieve in liquid soap than solid which is at less risk of falling apart after saponification (another wild guess is that because the water rapidly gets used up after trace making it difficult for it to fall apart and react with something else). The reaction, in my opinion would be facilitated by water (I did mention I am not a chemist, right?). Or it may be my relative lack of experience with liquid soap speaking.

This soap bar foams nicely too, though if I had to do it over, I'd probably superfat it less. The liquid soap had sort of died at that Ph.

I will update again after I send it :)

Vidyut said...

Time to eat crow. Ph of the soap is 7.3. I have no idea how this happened. It was ph7 two days after making. Thought I'd test again before sending. I confess a small, arrogant part of me was even thinking it may have dropped further, as soaps drop ph during cure... Never seen a soap increase ph after cure before this. All I can guess is that something happened to all that nice honey as it cured :(

At least it didn't fall apart :p

So I guess that challenge continues to remain unmet :D

Susan Barclay-Nichols said...

Hi Vidyut! Thank you so much for coming back and commenting about your experiences. It goes a long way to learning more about this idea of soap and pH.

Toyin Animasaun said...

Thanks Vidyut for coming back to share your experiences. Curious though, did you eventually enter the soap into the challenge? What did Dr. Dunn say?