Ageing soap

Can anyone explain what exactly happens during the cure besides water evaporation? Why does it become milder as it ages?

It completes saponification. Only 98% of saponification occurs by the time gel phase is complete(if I recall correctly). That 2%, apparently, is the difference between a so-so soap and awesome as far a mildness goes.

Not only does the soap get milder, but the lather gets richer and more long lasting. This I do not know why, but I have proven it to myself over and over.

Also, by losing the extra moisture, you get a longer lasting bar of soap.

So how long does it really take to complete the saponification? Weeks? Months? Generally speaking that is. I assume that it will be different to some degree for each recipe. After that period is it all just moisture loss, or is there still "something" going on?

I've heard that complete soponification can take 2-3 days...don't know that I believe that or not but I always cure my soaps at least 4 weeks and in most cases 6.

I think theres more going on that just saponification, in my tiny little mind.
If you've ever made beer or wine, you learn that it REALLY isn't ready when fermentation is done, it needs to sit for a month or five to become really tasty.
I think of it the same way as with soap, when saponification is done, you can lather with it, but its not done yet - needs to sit a bit to become really nice. Maybe its that last 2%, maybe theres something more.

During the cure time, as everyone knows, the soap dries down to a more-or-less stable weight that will vary some depending on the relative humidity of the air.

Residual lye will be consumed, but not necessarily in a saponification reaction (reacting with fat to make soap). Some excess lye reacts with carbon dioxide in the air to form soda ash. In an ongoing thread about non-gooey castile, we are also finding out that far more lye can be neutralized than can be explained just by soda ash formation or saponification.

The soap also hardens. Some of this is just simple moisture loss, but in my recent reading I'm learning that soap goes through a crystallization process that also contributes to hardness. Commercial soaps are hardened and the crystal structure developed mainly by mechanical means -- by milling and mixing. Handcrafted soap becomes more crystallized given enough time.

The development of this crystal structure also allows the soap to lather better, especially with the superfatted soaps that we typically make. Even though I'm still hazy on the chemistry, I know my older soaps really do lather more freely. The difference is especially noticeable with soaps I've made with have a high % of lard. Lard soap doesn't lather easily when the soap is young, but it lathers beautifully when it's older.

I must admit, I thought from the thread title it was a really bad idea for a new soap! Or a good idea, if you sell it to people who want to look older. It would still class as a cosmetic, with claims like that, though.

The Efficacious Gentleman said:

I must admit, I thought from the thread title it was a really bad idea for a new soap! Or a good idea, if you sell it to people who want to look older. It would still class as a cosmetic, with claims like that, though.

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So, selling to 19 & 20 year olds who want to pass as 21?

//end hijack

people have been known to buy weirder things than aging soap. but that was unfortunate wording on my part. i did not notice it.

deeanna, thanks for your answer. i was not aware that soap goes through a crystallization process. please do share more info.

DeeAnna said:

The difference is especially noticeable with soaps I've made with have a high % of lard. Lard soap doesn't lather easily when the soap is young, but it lathers beautifully when it's older.

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That's a handy thing to know. My very first soap experiments were mostly lard and when I tried using them I found you had to work to get a lather from them. Of course, being impatient I had only waited a couple of days to try them out. Now the rest of the bars are starting to age a little I may go back and try another one to see if it lathers more easily now.

The Efficacious Gentleman said:

I must admit, I thought from the thread title it was a really bad idea for a new soap! Or a good idea, if you sell it to people who want to look older. It would still class as a cosmetic, with claims like that, though.

Click to expand...

Pure coconut oil soap with a -30% superfat - perfect to get that leathery, aged look!

Ah, I found that other thread that DeeAnna mentioned and am taking the time (quite some time actually) to read through it.
Very interesting.

Saurian -- I made a recipe that was 90% lard, 10% coconut, with beer for the water phase. About 4 weeks after making it, I gave it a "C" for lather in a hand washing test -- pretty sparse and unexciting as lather goes. As time went on, I started giving it an "B" grade, mainly for its dense long lasting lather, as you'd expect from a mostly lard soap. Even though it lathered better, it still didn't earn an "A" overall. I had other soaps that I liked better. It's been about a year, and I pulled out one of the last bars the other day thinking "Aw, just put it in the shop and use it up" because I had formed a lukewarm opinion of this soap. Boy, was I in for a surprise. It now has a nice balance between fluffy and dense lather, it lathers up quickly, and leaves my skin feeling good after I rinse and dry my hands. The bar is silky smooth in my hands as I rub it to lather up. It doesn't "mush" if it stays a bit damp. Some of this I could have predicted a year ago, but not the change in the lather quality. It rates an "A" now.

Happysoap -- The crystal structure of soap is really interesting if you're a science geek. I don't yet speak the language well enough to explain it on my own, but I'm working on it. One good article to get started is Kevin Dunn's 2009 lecture about "Time and Temperature" in CP soapmaking -- he talks about the layered (lamellar) liquid crystal structure that soap creates when it gels. Here's a link to the lecture transcript: http://cavemanchemistry.com/HsmgTemperature2009.pdf The book I'm reading is Soap Manufacturing Technology by Luis Spitz, editor. See: http://www.amazon.com/dp/B00CIXV54M/?tag=skimlinks_replacement-20

Thanks Deeana. I read the lecture. I understand a little better the whole concept of gelled and non gelled soaps. I usually soap with a water discount and I had noticed that gel phase happened very rarely. I am still fuzzy on the crystal structure but its a good start. Great information. Thanks