Teach Soap

Hi Folks,

My curiosity is at work again. Has anyone ever calculated the weight loss in a batch/bar of soap over time. I know we leave our soaps to dry to make them last longer and that they get lighter during that time. I'm curious if it is possible to predict the "dried" weight from a % calculation. I'm also curious as to how much of the water we use in the recipe remains - perhaps discounting influences the outcome. Does anyone have this information?

All help gratefully received.

Cheers,

Grant

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Cheers,

Grant

He is no fool who gives what he cannot keep, to gain what he cannot lose. [Jim Elliott]

My soaps lose about 20-22% of their weight as they cure, unless I use a steep water discount.

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Linda
I know the voices in my head aren't real, but they sure have some great ideas!

Hi Linda,

Thanks for the reply. That's helpful. I'm guessing you probably start with about 30% water. So it might be a fair guess that the soap retains something in the region of 5 -10% water. I wonder if that is inevitable? Perhaps it might all evaporate out if left long enough. It would interest me to know but it sound like a long term project that I'm ill equipped with the necessary patience to perform. Perhaps the Castille makers in the group know. I believe it is best used after a year or more?

Cheers,

Grant

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Cheers,

Grant

He is no fool who gives what he cannot keep, to gain what he cannot lose. [Jim Elliott]

Yes, 30% water is about right. I have some bars that are several years old and they weigh the same as bars that have cured for 8 weeks, so there doesn't seem to be any additional water loss after a certain point.

As for castile, the longer cure the better. The first time I made 100% olive oil soap I experimented by washing my hands with a bar of it once a week starting at 8 weeks. It was nasty and slimy at first, but by the time it hit 6 months it was much nicer.

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Linda
I know the voices in my head aren't real, but they sure have some great ideas!

Aha! Very helpful. Thanks for the info. I'm off to play with numbers now.

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Cheers,

Grant

He is no fool who gives what he cannot keep, to gain what he cannot lose. [Jim Elliott]

So I've had a bit more of a think and a play with the numbers. It seems that theory and practice are in harmony. If we assume water is added as 30% of the weight of the oils then this equates to 23% of the weight of the raw soap (ignoring lye, fragrance and colours which would make it proportionally smaller again). Thus, if all the water were to evaporate then we would see a weight reduction of a little less than 23% - just as Linda reports!

Ta dah! QED, as my old mathematics teacher used to shout. It seems ALL the water evaporates during the 8 week cure. This would be borne out by the lack of change over time beyond 8 weeks.

This would give us an easy way to check when we could assume the weight is stable. Divide the weight of the non water ingredients by the number of bars (whole + wastage) and compare that to the weight of a cut bar. If they are close, or even the same, then they can be assumed to be stable. Of course, this assumes the bars are the same volume (size and shape). It helps me because I've never had the variation issues that Terry has been having with the commercial soap cutters.

Many thanks to Linda for helping me out on this. It might seem a small thing to most folk here but I like order and predictability. My wife says I have "CDO" which is a severe version of "OCD" where the letters are in the correct order. I hope this helps someone else too.

So, now to figure out what "maturing" process is happening beyond 8 weeks for Castille soaps to remove the sliminess.

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Cheers,

Grant

He is no fool who gives what he cannot keep, to gain what he cannot lose. [Jim Elliott]

If you do a steep water discount, the soap will harden faster and there will be less weight loss. With that said, curing soap is more then just water evaporation. The pH of soap changes slightly as it cures. The soap becomes milder. My skin does not tolerate newly made soap, no matter which method. That same soap works fine after a 4-6 week cure.

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Irena
Closed minds are like faulty parachutes; they refuse to open.