Weight loss method for testing cure

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BodyDew

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So I have always used the 4-6 weeks guideline with the testing for weight loss.
My question is...there seems to ALWAYS be weight loss, even after 6 weeks, so are we talking about a MAJOR weight loss? not just 0.5gms or less?
 
Soap will continue to lose weight over it's life cycle. Typically the majority of weight loss is 15% during the first weeks of cure. The more important factor of curing is the soap crystalline structure. I cure my soaps until they start performing how I want them to - lather stability, and skin feel are my two biggest criteria.
 
A couple of years ago (may 13`th 2019 to be exact, lol) I made a batch of soap, just 1 kilogram (2.2lbs) to test out 30% coconut oil instead of my usual 23-25% that I have been using for years and years. I wanted to see if it dried my skin out (it was actually fabulous soap, but I understand that others have a different type of skin that can`t take that much coconut)

Anyway - I decided to save one bar to keep a record of water loss during cure, and have been weighing it for the past two years. I have plotted down the numbers on a list, so I can post them if anyone out there is interested? (I can add the recipe too, in case anyone want to see it)

But for now I can tell you that the waterloss has continued, but has now slowed down to almost a halt.

I will keep this soap for at least 5 years more, and weigh it once a year, just to see what happens (because, you know, soap).
But I will not expect the soap to lose much more weight from here on out.

So to answer your question; a bar of soap will continue to lose water as long as there is water to lose.

However, the speed/rate depends on the composition of the soap (clays/pumice or other add-ons that grabs on to water and traps it inside their pourous grains), the recipe (oils/water/lye ratio), startweight (how thick/big the bar is made/cut) and the size of the cut surface itself will dictate how long the soap will continue to lose weight.
A flat, small bar of soap of 30 grams will lose weight faster. A big, thick chunky bar (6.oz like this one) will take longer.

I made the cut bars much bigger that I like to hold in my hands, but since my husband has huge hands, he prefers this size. (he is 6′ 3, so no wonder) so it will take longer to lose weight.
 
There will always be some weight loss due to evaporation. At some time, weight fluctuation due to atmospheric moisture might become noticeable (if you have scales that are precise enough). Keep in mind that the natural glycerol in the soap has the habit to attract water from the air, if only on a low level.

Weight loss won't “stop” by itself. It's happening more than half a year in: HO sunflower CP castile, testing the next natural green dye, and new mould!

Balanced recipes are mostly cured after 4 weeks, and after 6 weeks even more so, although evaporation is still going on. It's technically “finished soap”.
That might be unsettling for those selling soap by weight, and fearing customers to complain about being “defrauded” – though they just have witnessed natural moisture exchange! An alternative is to indicate dry weight/the amount of oils you've put in in the first place (a number that won't change with weather).

ETA: @amd and @Bubble Agent were a tad quicker 😉
I have plotted down the numbers on a list, so I can post them if anyone out there is interested? (I can add the recipe too, in case anyone want to see it)
YESYESYES :nodding:
 
So I weigh my soaps daily from the day they are cut & the weight loss gradually gets less as it should be. But I'm assuming that after 4 weeks, if the scale is barely moving then waiting another 2 weeks isn't necessary?
Reason I'm asking is because I constantly have friends asking "How much longer before my soap is ready?" (I thought I was impatient during cure, but WOW they are much worse - lol)
 
Hrm. Two types of impatience. Soap is usually safe to use after as soon as a few days. It only gets better with time. For most recipes, experience shows that it has presentable performance after 3 to 4 weeks, but it really pays off to give it another week or two, that's where the 6 weeks come from AFAICS.

It is not wrong to use soap earlier, but keep in mind (and spread) that people tend to judge things from their first impression, and when your first impression is too early for the soap to flex with its strengths, then you (or whoever feels appropriate to be impatient, lol) are judging it under its capabilities. A four-weeks-old bar of soap has probably a hard time to convince someone how much better DIY soap is than industrial store-bought soap. Those who don't mind – can go on using it early.

The tricky thing is to judge when the curing period is over. Unfortunately, there is nothing special happening around the 4–6 weeks mark. It is more a convention, a loose rule of thumb, that by this time, most lye-based soaps have surpassed the impression that an average industrial soap leaves. Weight loss from evaporation might help you debug recipe experiments, but is only a rough measure of curing progress. Keep in mind that drying (water loss) and curing (reorganisation of soap molecules) are two separate processes that just happen to take place in the same stage of life of a soap bar, and not necessarily at the same pace.
 
So I weigh my soaps daily from the day they are cut & the weight loss gradually gets less as it should be. But I'm assuming that after 4 weeks, if the scale is barely moving then waiting another 2 weeks isn't necessary?
Reason I'm asking is because I constantly have friends asking "How much longer before my soap is ready?" (I thought I was impatient during cure, but WOW they are much worse - lol)

One advice I would give you is; don`t hover over the scale, worrying about how much or little weight the soap loses from week to week, wether it is a gram or more. You can not tell if a soap is done that way.

Think about soap as a cake. Some cakes are light and airy, needing shorter time in the oven. Then you have your heavier cakes, with lots of butter, flour and a hefty helping of sugar. The timer may go off, but that doesn`t mean it is ready. So you stick your knife or toothpick inside it and see that there is batter clinging on to the toothpick. Ok, it needs more time. As time passes the cake is getting firmer and you check on it again. Ok, it need a bit more time still....

Soap is like that. It have to take the time it needs. It is not like x grams of weightloss in one week equals exactly x % ready soap.

So really, the best thing you can do is to get to know your recipe/soap, test over time and see how it behaves when you wash your hands with it after 4 weeks, 5 weeks, 6 weeks etc.
No matter how impatient your friends are, just tell them that you want to give them a high quality product to try, and that process can`t be rushed. Just like you don`t want to serve them cake that is uncooked in the middle.

You will find, no matter what, that the soap will improve over time, even though the water loss may not be huge from day to day or week to week. More bubbles, easier to get it to suds, rinses off better, and other factors.

@amd said it wisely, "The more important factor of curing is the soap crystalline structure."

Unfortunately you can`t set your timer to go off when that has happened, so that is why you need to see how your soap and recipe behaves over time.

My recipe will be quite good at 4 weeks, much better at 6 weeks, great at 7, and awesome at 8 weeks (12 is wowsah..)
But I don`t give it away until it has matured for at least those 7 weeks. But that is because those I give my soap to they use it straight away (no hiding them i sockdrawers of linen closets for three years) so I want them to experience great soap right of the bat.

PS! Why not measure the soap once a week instead of every day? You`ll see more progress that way. Think of it as being on a diet. If you weigh yourself every single day you will not see much improvement. But once week will reveal more of the progress.

YESYESYES :nodding:

Shure thing! I will do tomorrow though, it is nighttime here now.
 
If you are thinking of selling your soap, and need a weight for that, I used the phrase "At least 4 oz." Just pick the lowest weight you think it will drop to, and subtract 0.5 oz (or 14 grams). The weight does not have to be super specific, the bar just does not need to weigh less than what the label says.
 
As for selling and labeling soap weights, I weighed each bar after curing and always deducted another 6% depending on the size of my bars. I knew my bars would lose approximately another 6% after about a year.
With labeling laws unless this has changed, you cannot use the words approx, at least, (sorry Susie), about, not less than, etc. You need to use Net Wt xxx. so you want to be comfortable with labeling a weight your bars will be if someone lets them sit around a long time and they decide to weigh them, keeping in mind a thin cut 1" 4.5-5 oz bar will lose more weight than a bar cut 1.25" with a start weight of 5.5 or more. My bars used to start out around 6-6.5 oz.
 
Hmmm.. I have my notes and recipe here with me now, and was going to post my finding.

But then I was thinking; Would it be better if I just made a separate thread for my experiment? I am more than happy to post it here, but if I make a separate thread it could be kind of cool to be able to update the thread with further weightloss or other things that may happen to this soap as time passes.

Or, what do you guys think?
 
My shave soaps are a semi-soft type, better the ability to produce a rich, thick, creamy lather for better glide and lubrication.
They're a "dual-lye" process and therefore need to stay semi-soft and slightly tacky.
I let the cut pucks cure for a couple of days, then wrap them in plastic film wrap (I will probably be vilified for that but it's necessary for the puck to remain semi-soft). However, I do let them continue to cure wrapped up to allow the soap crystals to fully develop for a minimum of four weeks.
 
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