Curing process

[Erez]

Hello. After having some unexpected results from my soap, investigating a bit and from answers from this forum I got to realize that the part of the curing process isn't clear to me at all.
Could any of you explain what's going on while curing better for me? To my understanding it's only drying out of water and so some questions remain not answered for me.

How come it's changing it's properties? When I'm adding water to a "cured" soap why doesn't it act as an "uncured" one? (Slimy texture, lather etc.)

How come different oils have different curing period? Is there a table showing each oil's period?

Is there a way of shortening the curing period (temperature, fans etc.)?

Is there a "good"/"bad" curing process, could it be done wrong or is it only uncured or cured?

Thanks a lot. Erez

 

[DWinMadison]

My understanding is the during cure, two things are happening: Sopanification finishes and drying occurs. The former is dependent on your oil/lye (sf) ratio as well as the melting point and density of oils used. The later could be shortened by discounting water in your recipe. Does that help at all?

 

[jcandleattic]

No, curing is so much more than "just" the evaporation of water. Your seems to be changing properties because it is.
Even though there is not any active lye in a properly made soap, there is still a chemical reaction going on in that soap. Which is why with time soaps become milder and much nicer to the skin than newer soaps.

Different oils have different curing time (eg: Olive Oil) because they have different properties and the chemical reaction to make them mild and to harden up the soap takes longer.

You can shorten the evaporation time with fans, etc, but no, that will not shorten the cure time. Not if you want your soap to be the best that it can be.

IMO direct sunlight and extreme temps and very humid conditions are not optimal conditions for curing soap, but other than that, no, I don't believe there is a "wrong" way to cure them...

Hopefully this helps, and I'm sure others will chime in with more specifics that will better explain what I'm trying to say.

 

[Seifenblasen]

What kind of unexpected results did you get?

There are many scientific explanation to the curing process, such as water continues to evaporate (to make for a harder bar), that the very tiny last bit of unreacted lye continues to saponify the oils, and even an extremely small amount of lye reacts with air to form sodium carbonate, etc. To answer why adding water to cured soap doesn't make it behave like uncured soap, it is because the saponification process is a non-reversible reaction. An analogy would be like baking (heating) a cake - letting it sit out in the cold will not reverse the process and turn it back into batter.

Most people agree that a dry, warm place with good air circulation is best for curing. You may be able to shorten the curing time a bit (say, a week or two) with the ideal condition.

I am normally a science geek in soap making (having worked as a R&D chemist when I was younger). But when it comes to curing, I tend to consider soap like cheese or wine - in addition to the science, there is an art to it, best understood by experience and feel. :wink:

 

[AlchemyandAshes]

The Curing Process seems to cause a bit of a debate here on the forum. And really, there aren't lots of lab studies to back up either side of the argument, but there is lots of anecdotal evidence to support curing.
Yes, a lot of the curing time is used evaporating water. I think everyone agrees on that.
Perhaps the other benefits of a 4-6 week cure are due to that water evaporation. Here are some opinions from "experts" that you may find helpful:

From SoapQueen.com

Curing: The process of curing CP soap allows the excess moisture in the bars to evaporate, leaving a harder and longer-lasting bar. In chapter 21 of Scientific Soapmaking, Prof. Dunn notes that the total alkali of raw soap batter is about 10%, and that the total will fall to below 0.1% within an hour if the soap is held at 160 degrees. A zap test – sticking your tongue on the soap to test for a “zap” or lye reaction – or a pH test will confirm this. However, the earlier a bar is used, the softer and possibly slimier the bar will be in the shower, and the less time it will last. Additionally, the 4 to 6 week curing and drying time helps to produce the most gentle bar of soap possible. You will notice a difference in your skin when showering with a new bar of soap versus a fully cured and dried bar. It’s the final bit of pH lowering that happens in the rest of the 4-6 weeks of curing, and the main benefit of the cure time is the evaporation of excess water, which makes for a harder bar and a more true net weight for labeling purposes if you’re selling your soap. So if you’d like a harder bar, allow your soap to go through the standard 4-6 week cure.

From http://thesoapbar.blogspot.com/2009/01/force-curinghardening-after-fact-help.html , Anne-Marie Faiola (Soap Queen TV and Brambleberry owner):

Anne-Marie said...
I am totally going to be the grinch that stole the short cure time but this phrase, "I made a soap with butters and olive oil a few weeks ago." is the heart of the problem.
There is a reason that cold process soap requires a 4 to 6 week cure time.
1. It allows all the excess water to leave the bar. The water is primarily there as a vehicle to help move the lye around. Once the soap is made, this extra water evaporates out, over time, leaving a harder bar.
2. The last 3% of pH lowering time takes place in the last few weeks of cure time. If memory serves me correct, Kevin Dunn of Soap Guild Speaker fame gave a talk 5-6 years ago at the Guild. I think this is an accurate recollection of his talk. If it's not, someone please correct me for the good of the whole group. =) He has done extensive testing that proves that most all of the saponification reaction takes place in the first 30-60 minutes, during the initial trace phase. However, that last 3% to really get the soap to a great pH that is skin loving (as opposed to skin drying) does take that extra 4 to 6 weeks which is why to get the best, most mild soap, we wait 4 to 6 weeks.
You could probably put the soap in a drying chamber (silica beads in a airtight container) to try and get the soap to dry out faster but that won't lower the pH and make the bars exceptionally mild.
I hope this helps. I'm traveling today and tomorrow but will check this blog to see feedback and response to this issue. I'm really interested to see what everyone has to say about it. It's a great question that affects many soapers. =)
January 22, 2009 at 12:03 PM

Kevin Dunn - author of Scientific Soapmaking (you may find this book helpful)
http://cavemanchemistry.com/soapforum/index.php?topic=6.0

 

[Erez]

Sorry for the great delay and thanks a lot for the replies.
I still have two questions though. My Soaps cure for much more then just 3-4 weeks. I have soaps 2 and 3 months old that still haven't cure fully.
I make my soaps form olive oil and I understand it takes longer to cure. Is there any table or something that lists all the oils by their curing time? How long for olive oil to cure? Sunflower?

Another question for you, I make my lye solution by a 1:2 ratio, can I use less water then that?
Thanks a lot!

 

[Seifenblasen]

Sorry for the great delay and thanks a lot for the replies.
I still have two questions though. My Soaps cure for much more then just 3-4 weeks. I have soaps 2 and 3 months old that still haven't cure fully.
I make my soaps form olive oil and I understand it takes longer to cure. Is there any table or something that lists all the oils by their curing time? How long for olive oil to cure? Sunflower?

Another question for you, I make my lye solution by a 1:2 ratio, can I use less water then that?
Thanks a lot!

What do you mean by your soaps is not fully cured after 2 or 3 months? Are they still soft, or harsh, or ?

I have 100% olive oil soaps that are still not cured to my liking after almost a year and will let them cure longer. As far as if there is any table that list the oils and their curing time, I am not aware of. Furthermore, there are so many other variables, such as humidity, temperature, air flow rate, etc. in your curing area, additives in your soaps such as honey (a natural humectant), clays, essential oils, sodium lactate, etc. The size of and shape of your soap also makes a difference (at least where water evaporation rate is concern) as intuitively the bigger the surface area vs. volume ratio is, the faster soaps dry out.

Without further detail on what kind of unexpected results you get from your soaps, and what you mean by not fully cured after 2 or 3 months, and what kind of oils (100% olive or just a high olive content) you use in your soaps, it is difficult to give you a real answer.

As far as lye solution, I have gone as low as 1.2:1 (1.2 parts water to 1 part lye). While it leaves the soap less water to evaporate out, such low water content would also inhibits gelling, and ungelled soaps usually requires a longer curing time.

 

[Erez]

HI.
By unexpected results I mean it turns slimey.
I haven't understand about the gelling you said this ratio inhibits. What's gelling?
I'm using 100% olive oil.

I'll try other oils just to experience. If you say that your soaps also take a year to cure then I guess I'm fine. I think it's interesting to understand what makes them so different from other oils. Someone here said it's "castile" but I haven't figured out what it means.

Thanks a lot.

 

[houseofwool]

A Castile soap is one made with 100% olive oil. Castiles are known for having a slimy lather without big fluffy bubbles. Most castles benefit from a really long cure, 6-9 months or more.