DeeAnna you are once again my hero....thank you for your clear concise presentation. You are so very much appreciated. You make thinks so much easier to understand. I will contine to use the zap test. I've been doing it for years and won't stop now. I figure if I haven't been burned by now it's not happening....
Actually, she didn't prove, nor disprove anything about the zap test.:yawn:
"No, it's really, really not that simple.
Soap is a buffered system, not a straightforward acid-base system, which you appear to think is the case. Furthermore, soap is a colloid, with its own unique chemistry.
The pH of a soap will fall in response to added acid IF and ONLY IF there is excess alkalinity. Once the alkalinity of the system drops to the natural, intrinsic pH of the soap system, the pH will REMAIN STABLE even as more and more acid is added. During this phase, the soap instead will maintain a stable pH by breaking down into its constituent fatty acids as more acid is added -- that is what a buffered system does. Only after the soap fully converts into fatty acid will the pH drop once again in response to additional acid."
Actually, it REALLY IS that simple. You're assumption that I think soap is a simple acid/base solution is interesting...where did you get that from? Also, you use this word intrinsic in relation to soap. It's a throw off, as though you think soap has some special internal ph combined with some other ph. It doesn't. While yes, each fat will bring something of it's own to the table, including it's own ph, in the end, they all will contribute to the FINAL ph of soap, along with any other ingredients used. It's that final ph of soap that we are discussing here. Not it's individual constituents. Anyways, while yes, in a set of simple acid/ base solutions, as I'd worked with yesterday, the ph will more easily rise and fall with the addition of an acid or base, that doesn't mean the soap won't do so as well with the addition of an acid or base. In fact, with LS making for example, a common solution with troubleshooting excess fatty acids in soap, (which by the way, if you test ph on will have a lower ph than a fully saponfied soap) is to add more lye, thus fully saponifying the excess fats, and raising the ph. Or in the case of excess lye, which can only truly be found out with a ph test, is to neutralize it with an acid, thus lowering the ph. By the way, I've zap tested a soap with a known lye excess, and thus, higher ph, nothing.
When I say neutralization, you must be confused with soap straight out of the pot as opposed to actually neutralizing the soap to a more acceptable pH level. I was referring to actually lowering the ph to the level that is more acceptable, if at all possible. In HP and LS making, it is most certainly possible, through the use of neutralizers like borax, boric acid or citric acid. CP, however, isn't as easy, but it is possible none the less, either through rebatch, or adding an acid during the making process:
http://forum.thesage.com/comments.php?DiscussionID=99
An excess of lye, or hydroxide ions, isn't necessarily needed in this case however, if you just use sodium, or potassium citrate, which can be purchased in anhydrous forms. Otherwise, the NaOH SAP value of anhydrous citric acid is .625, while monohydrous citric acid is .571
" Again, this is a dilute solution and is the correct way to measure soap pH."
No, it is not the only way. As indicated in the MillerSoap links, the author used BOTH a 1% solution and a slurry. She made note: "Since most of us [soap makers] don't test pH using a 1% soap solution, I also tested each strip by making a slurry with distilled water directly on the bars of soap. I did each set of tests twice, just to be sure." Her results, using strips and a lab meter, were consistent across the board.
She further gave simple instruction on the proper way to use strips to get better readings:
"Recommendations for using test strips:
Some test strips need longer contact with the solution/slurry for an accurate reading. For best results, keep your test strip in the solution/slurry until the color no longer changes, perhaps 30 seconds or one minute.
Store your strips away from direct light which over time, can fade the dye indicators and interfere with accuracy."
It is also noted that lab grade strips are best.
It's quite contradictory to say this:
"If one cannot accept the fact that a well made, skin safe lye soap may have a pH of 10 or above, then don't make or use lye soap. "
Then turn around and say this:
"The one statement you make that I agree with is that pH is correlated with skin irritation in
sensitive individuals"
You have pretty much agreed that a higher pH results in skin irritation, and is therefore not skin safe, with that last statement.
As I've said before, a pH of 10 IS NOT skin safe, as stressed to me by friend with a degree is biomedical engineering. Skin damage is occurring at a molecular level, that is of course most apparent to individuals with sensitive skin. But it doesn't mean it isn't happening to the general population with normal skin. Damage is occurring whether it is noticed or not. In fact, considering skin ph is roughly a 5, anything too much higher than that really isn't good for the skin either. But, in the case of soap, going below 9 is difficult without the soap beginning to breakdown, but that's more likely if you were to a straight acid to the soap, rather than an acid salt, like sodium citrate or sodium borate.
http://skincarerx.com/101-ph-article.html
http://www.livestrong.com/article/152255-ph-effects-on-skin/
In regards to the use of phenol-p drops to test for safety:
http://soap-made-easy.com/soap-ph.html
And technically, on a pH scale of 0-14, 7 being the 'perfect neutral", the scale is actually broken up into 3 parts, or zones, depending on what the source is for the scale: acid zone (0-4), neutral zone(5-9), and basic zone(10-14). With most bodily fluids( stomach acid not included) , and skin, falling in the neutral zone. Even water, considered to be neutral at 7, depending on temp changes, can be either "slightly acidic" or "slightly basic". Water at 25*C has a pH of 7, while at 50*C a pH of 6.55. Note, however, that water that has been exposed to air is mildly acidic. This is because water absorbs
carbon dioxide from the air, which is then slowly converted into
bicarbonate and hydrogen ions (essentially creating
carbonic acid).
And I found this website quite interesting, with lessons and tools to help better understand what happens when pH changes.
http://phet.colorado.edu/en/simulation/ph-scale
And more information on the effects of high pH on skin.
http://www.womensforum.com/alkaline-skin-danger.html
To me, this is no laughing matter, or something to be swept under the rug We make soap for various reasons, but more likely because we don't want to use synthetic products or there are allergies involved. Or we just want to know what goes into our soap, to have control. Just because soap, out of the kettle, automatically has a high pH, does not mean we can't make the attempt to lower that pH to more skin friendly/compatible levels. That to me is not acceptable, and it does a disservice to our families and friends whom we gift these products to. And if you sell your soap, you are further spreading an issue to customers. In the old times of making soap, folks then didn't have the knowledge, or ability, to change the harshness of their soap. To them, it was what it was. If they zap tested but the soap still "took the hide off of folks", oh well. We have the means to do better than that. Which is why we have companies like Dove, making the 'perfect neutral soap". Should the choice be made to find out what those means are as home crafters, that's up to the soap maker. I'm choosing to educate myself, apply what I know, and further educate new soapers, that zap testing is not acceptable in our modern time as it will not tell you what the pH of your soap is, and a high pH is not skin safe, and that there are ways do the opposite.
Thank you, DeeAnna!
