water reduction and cure times

[DeeAnna]

About 100 g of water is the practical minimum. A 50:50 solution -- 1/2 NaOH and 1/2 water by weight.

 

[kazmi]

Here is the dry time graph updated through today. My test bars are still losing weight incrementally, but the curve has really flattened out. Interestingly, the bar with the higher original water content has stayed higher throughout the dry time and appears to be reaching equilibrium several percentage points above the other bar. I would have expected it to catch up at some point. Granted, this is one trial so no trend has been established, but I find it interesting. I think I see distinct phases in the curves, with a high rate of loss in the first 3 weeks, then a secondary phase from 3-14 weeks. At about 100 days the rate flattens again with much slower changes from then on.

Thanks for sharing your results! How long are you planning on carrying out your study?

 

[Timber]

Probably until Christmas, when most of my cured bars will get wrapped and put under someone's tree

 

[pamielynn]

forgot to quote the comment I'm replying to.

I would never suggest going less than 50:50 water to NaOH either.

 

[Soap Techniques]

A soap made with "brittle" fats -- coconut oil or palm kernel oil -- will be relatively hard ... but it will also be very soluble.

A soap made with soft liquid oils -- monounsaturated oils (olive, almond) or polyunsaturated oils (safflower, sunflower, corn, etc.) -- will not typically be a hard soap, but it will be a less soluble soap.

DeeAnna, then why does a soap made with just soft liquid oils get more mushy in the soap dish, than a CO or PKO bar does?

 

[DeeAnna]

"...why does a soap made with just soft liquid oils get more mushy in the soap dish..."

As I explained in my first post in this thread, there are two factors that contribute to long lasting soap -- physical hardness and water INsolubility. Soaps made with soft oils are relatively INsoluble, but they are not especially hard.

If you leave any lye soap in a puddle of water in the soap dish, the soap will get mushy. Soaps made with mostly lard, tallow, or palm (palmitic and stearic) will get mushy somewhat slower than soaps made with mostly CO or PKO (lauric and myristic, harder but more soluble) or soaps made with monounsaturated or polyunsaturated oils (oleic, ricinoleic, linoleic, and linolenic; softer but less soluble).

Other factors will also affect the "mushy factor" of a particular soap. Probably the biggest is cure time -- young soaps mush up faster than well cured soaps, all other things being equal. You'd also need to look at the method (CP non-gelled soaps mush up faster than HP or gelled CP soaps), the lye solution concentration (full water soaps may mush up faster than soaps made with 33% or 40% NaOH), any additives, etc.

Not sure I've answered your question....

 

[Soap Techniques]

If you leave any lye soap in a puddle of water in the soap dish, the soap will get mushy. Soaps made with mostly lard, tallow, or palm will get mushy somewhat slower than soaps made with mostly CO or PKO (hard but more soluble) or soaps made with monounsaturated or polyunsaturated oils (soft but less soluble).

Thank you for the answer DeeAnna. From my experience soaps made from soft oils get mushy faster than any other soap. Right now I am using an experimental bar made with 100% canola oil. For the recipe I used the same amount of water I usually use (33% lye solution) and cured it for 4 weeks. It gets much more mushy in the soap dish than a 100% CO bar does (the same amount of water & 4 weeks of cure). I could say the same about slime... My castile is also slimier than my CO bar, even after long cure.

So regarding how easily my soaps get mushy and slimy, I would range them in this order:
1) mostly soft liquid oils
2) mostly coconut oil
3) mostly lard, tallow, or palm

Based on my experience I would say that soaps made with mostly liquid oils are the most soluble.

 

[Soap Techniques]

P.S. When some people complain about soap being slimy - it's always about castile/bastile. I've never heard complains about 100% CO soap being slimy. Doesn't it have anything to do with the soaps solubility?

 

[LoveBIRD]

Discounted Water

One benefit to discounting the water is also to avoid a ton of shrinkage during the cure... the more water you use, the more your bars will shrink in size and weight after you cut them. I like to discount the water in my soap so that my bars don't loose a ton of weight or size

 

[Timber]

Well, it has been one year (wow) since I started plotting dry times on these two bars. I did the final weights today and the bar with more water at the beginning still has more water at the end. Interesting...

 

[saffy]

Really interested in your drying data, thanks for sharing it.