Impatient Maths?

[MissE]

I have a recipe whose total weight was 748.49g.
150.3g of this was water.
I poured this into 5 individual molds.

If all the water evaporates during curing, it means I should be left with 598.10g of soap, that is, each individual soap should be 119.62g .

When I first popped them out of the mold they weighed 236g - 254g, and after 21 days, I have an average weight of 210g, so I have 90.38g more to lose for each soap . . . err . . . is this about right?

I'm sorry, I'm impatient and like things predictable :think::think:

 

[The Efficacious Gentleman]

Impatience and soaping don't always go together too well. You might have to learn to be a little bit more.

As for the water, I don't think it will ever lose the total amount of water, some will always be present. Water loss and cure are not the same. Soap is cured when it is cured, regardless of whether or not is is still losing some water or not. Castile needs about a year before many consider it cured, but it will have stopped losing a lot of water well before then.

 

[toxikon]

DeAnna had a cool post about water loss with a graph and everything, maybe she'll come share it!

 

[SaltedFig]

It is predicable, in an exponential kind of way .

Have a look at a picture of an exponential curve. This is the picture of a mathematically calculated (or measured) change, where the change keeps happening, but the amount of change decreases over time.

So ... to put that in English, the water will evaporate quickly at the start and the rate of evaporating will slow down over time.

Most of the evaporation will happen in the first few weeks, but the water will never quite completely evaporate. Eventually the amount of water that evaporates each day/week/month gets so small as to be almost imperceptible, and your soap reaches a state that could nearly be considered equilibrium (it really isn't going to change much at all anymore).

It is fun to measure and plot for each new recipe. You can build up a store of information on how your soap works for you. After a while, you will know roughly how much your soap will evaporate (as a percentage of initial bar weight) in a given amount of time.

This knowledge is very useful if you want to create a soap bar that has a minimum weight by the time your recipe is cured enough to be lovely to use.

I have a recipe whose total weight was 748.49g.
150.3g of this was water.
I poured this into 5 individual molds.

If all the water evaporates during curing, it means I should be left with 598.10g of soap, that is, each individual soap should be 119.62g .

When I first popped them out of the mold they weighed 236g - 254g, and after 21 days, I have an average weight of 210g, so I have 90.38g more to lose for each soap . . . err . . . is this about right?

I'm sorry, I'm impatient and like things predictable :think::smile::think:

 

[MissE]

Water loss and cure are not the same. Soap is cured when it is cured, regardless of whether or not is is still losing some water or not. Castile needs about a year before many consider it cured, but it will have stopped losing a lot of water well before then.

Do you mean when a soap is saponified, it is saponified? I've read everywhere that curing is simply the process of soap losing water (and becoming milder and better). With your Castile soap example, do you mean to imply that curing is more about the oils solidifying back (which takes longer for a high olive oil recipe)? I'm open to learning more about this and will be glad if you or anyone else can clarify further for me.

As for the water, I don't think it will ever lose the total amount of water, some will always be present.

I hear you when you say soap will never lose the total amount of water, but I'm hoping that when I start to get somewhere near the 119-ish mark, I can assume I am as close as I will ever be to water being completely dry from the soap.

I will have to see how close I get to that mark then and how long it will take! I hope to report back, too!

On another note, all this raises the question for me why water is never mentioned as part of the by-products of the saponification process if there will always be a small part of it left over? I always only ever read of the salt and glycerin?

 

[MissE]

DeAnna had a cool post about water loss with a graph and everything, maybe she'll come share it!

I hope she does!

 

[toxikon]

Do you mean when a soap is saponified, it is saponified? I've read everywhere that curing is simply the process of soap losing water (and becoming milder and better).

To mention DeAnna again, I learned from her that the entire crystalized structure of the soap changes as it cures - it's definitely not just water loss!

 

[MissE]

Have a look at a picture of an exponential curve. This is the picture of a mathematically calculated (or measured) change, where the change keeps happening, but the amount of change decreases over time.

Is there an image attached to this cos I can't see it . . . but I get the English translation, anyway, thanks!:bunny:

It is fun to measure and plot for each new recipe. You can build up a store of information on how your soap works for you. After a while, you will know roughly how much your soap will evaporate (as a percentage of initial bar weight) in a given amount of time.

This knowledge is very useful if you want to create a soap bar that has a minimum weight by the time your recipe is cured enough to be lovely to use.

Precisely why I'm looking into this. I want to print cheap labels with the net weight information and all that for my soaps so that when I give them out, family and friends can share my fun with making soap with all these ingredients! I intend to wait and plug in the net weight when it is fully cured, but it's just how come I came to be thinking about the numbers, and now I really want to see how predictable it can all be.

I suppose also that some of the weight will be owed to additives, dry additive like coloidal oats, for example, and while I'm thinking about it, I am wondering if purees can be measured accurately in terms of what part of them contributes to water weight and what part contributes to fiber weight.

I'm sure I'm overthinking this!

 

[The Efficacious Gentleman]

You are - for giving away you don't need the net weight.

Curing is about water loss AND the soap itself changing the structure and becoming better. In the Castile example, as I said, water loss will effectively stop after a while but the soap will continue to improve with age. So while both happen in a cure, they aren't strictly related

 

[DeeAnna]

<... looks up from contemplating my empty coffee cup ...>

Here's my cure time thread: http://www.soapmakingforum.com/showthread.php?t=35831
I have a revised and condensed version here: https://classicbells.com/soap/cure.html

<... pads off for a refill ...>

 

[MissE]

You are - for giving away you don't need the net weight.

Curing is about water loss AND the soap itself changing the structure and becoming better. In the Castile example, as I said, water loss will effectively stop after a while but the soap will continue to improve with age. So while both happen in a cure, they aren't strictly related

No, I don't need to, but I want to. It's all part of the learning process for me as I am keeping notes.

Thanks!

 

[jcandleattic]

No, I don't need to, but I want to. It's all part of the learning process for me as I am keeping notes.

Thanks!

If you want to add the weight to the bars you are going to give away as testers, and simulate the label as if you were selling, you really need to wait for the full cure, weigh them, and then label them or get your weight that way.

When selling, and adding net weight, it is okay to be a little off, only IF that amount states the bar is less than the actual weight, but not if that little bit is over the actual weight.
The whole "truth in advertising" etc., comes into play at that point.
Probably not the best practice to guesstimate on water weight that should/shouldn't evaporate out.

 

[DeeAnna]

It would be incorrect to assume all the water evaporates from soap, because that's not how the real world works. In addition, soap will continue to very slowly lose weight even after a generous cure time. But the largest weight loss is in the first month or two.

Most of my freshly cut bars weigh about 155-165 grams. They end up roughly 135-145 grams after cure, and I want them to be closer to the high side if possible. The net weight on my label is 128 grams (4.5 ounces).

It is fine to under-state the net weight on your label. In effect you're giving your customer more value for their money, and I don't know of any customer who would complain about that. Under stating the weight also allows for some weight loss after the soap is packaged.

 

[SaltedFig]

Is there an image attached to this cos I can't see it . . . but I get the English translation, anyway, thanks!:bunny:

Below is a copy of an exponential (decay) curve from intmath.com.

DeeAnna's in her linked thread above is an exponential (growth) curve.[FONT=&quot]
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[SaltedFig]

I intend to wait and plug in the net weight when it is fully cured, but it's just how come I came to be thinking about the numbers, and now I really want to see how predictable it can all be.

If you want, you could measure the weight of your soap bars at regular intervals to fine tune your estimate.

I reckon an estimate over 10% weight loss is going to get you reasonably close to reality, and 20% would likely give you a comfortable margin of error.

Good luck!

 

[MissE]

Yes, I weigh my soap every other day and I fully intend to keep doing so. I was just trying to understand the process of water loss so I can better relate to my ongoing observations.

Also, the impatience I spoke about was that of not waiting to the end to see what the soaps weigh but rather following the process with a scale and a notebook. I was not asking to know if I might be able to speed up curing time. However, I've learned quite a lot from you all about the three-fold meaning/benefits of curing soap.

My assumption about complete water loss came from the fact that most people who write about soap never mention that water will remain in the finished soap, which is obviously inaccurate.

Thanks, everyone, for your help.