2 year old soap, its gradual water loss during cure & beyond

[Bubble Agent]

I originally replied in this thread here, because someone asked about curing soaps/waterloss.

Since I already have a bar of soap I have kept track of over the last 2 years and 4 months I thought it could be nice to make a separate thread.
This is just for a bit of fun. I am not a scientist nor am I a math genious or a chemist. But I am one thing, and that is a person who loves soap.

Here is the backstory to my simple experiment:

May 13`th 2019 I made 1 kilogram (2.2lbs) soap to test out 30% coconut oil instead of my usual 23-25% that I have been using for many years. I wanted to see if it dried my skin out or if it worked out to be a pleasant soap. I have used that amount of coconut before, but then I was much younger! Now that I am getting older I wanted to try again. I found that this was great soap for me and my husbands skin. But I understand that others have a different type of skin that can`t take that much coconut. I will make this soap again for personal use. This is not a vegan soap, as it contains lard.

I will provide you with the full recipe and all my notes, so you can see what the numbers look like. You may not understand Norwegian, so I have writtend down everything that needs translating. And because, messy handwriting... (I have only showed you the pretty side up, lol)

I will just point out that this soap was great for us, we loved it. However, I am not saying that this is a great soap for everyone. You may find this soap drying, or there are oils you may not tolerate or have access to. But since this is just about water loss experiment for this specific recipe, the point is not to provide you with a wonderful recipe that is the be all end all of soap recipes in general. I am simply giving it to you as a courtesy so you can take a look for yourself.

Kind of like those who like to eat cake, and ask for the recipe. And others just likes to enjoy the cake itself, live in the moment and move on. I just gave you the recipe so you don`t have to ask for it

Moving on:

I decided to save one bar to keep a record of water loss during cure, and have been weighing it her and there for the past two years and 4 months. I have plotted down all the numbers on a list. The soap has continued with its waterloss, but has now slowed down to almost a halt, and needs bigger breaks between weighings.

I will keep this soap for at least 5 years more, and weigh it once a year (perhaps every 6 months), just to see what happens to it. Why?? Well, you know, it is soap and I am a curious cat. I will not expect the soap to lose a lot more weight from here on out, but some will still evaporate as the delicous crystallization structure realigns itself into neater rows of happy little soap molecules, pushing away more water, making the soap ready to puff up at the slightest cuddle of the good `ol H2O.

And after that? I will cut it up into three pieces, and test it as the years go by. Because, you know, bubbles! Click on thumbnail for bigger pictures.

Making of the soap 13/5-2019.

Start weight - 170 grams after cut, per 14/5-2019. (Stored on a curing rack in a dry, dark room, with free flowing air around it. Not covered.)

Measure #1: 23/5 -2019 - 164 grams
Measure #2: 4/6-2019 - 160 grams
Measure #3: 14/9 - 2019 - 158 grams
Measure #4: 20/6-2019 - 157 grams
Measure 25/6-2019 - 156 grams (6 weeks after making)

Note: From now on out - stored in a dark, ventilated room (another storage space inside the house, with ventilation)
Stable temps, no unpredictable fluctuations, and soap protected from dust with a lightly wrapped piece of tissue paper (pictured)

From here on out - random dates of weighing:

8/7-2019 - 154 grams
1/9-2019 - 151 grams
5/8-2020 - 143 grams
20/7-2021 - 140 grams
23/8-2021 - 140 grams

Additives: SG - 12 gr.
Table sugar: 2 tablespoons
1 teaspoon of salt
Kudzu fragrance oil

Colors:
1 teaspoon Blue vibrance (which turned into a muted blue because I added titanium dioxide. I regretted that later, it became dull)
1 teaspoon Jade green mica from Nurture Soap.
1 teaspoon yellow mica from Nurture Soap (can`t remember what it was called. It was an older one, it is discontinued a while ago. It faded terribly in this soap and made it beige, not yellow)
In the pot swirl, medium trace, gelled.


I have a habit of always writing down the dates for when 4, 6, 8 and 12 weeks has passed. Every soap calc sheet follows the soap until it is used up. Then it goes into a folder, for reference.

PS! I you are wondering if I weighed the soap before I wrote the weight of the soap underneath, I did. It was then 172 grams. When I wrote the weight on the soap, I did not lose a lot of soap, so I took a knife and cut it, checked the weight so it ended up weighing exactly 170 grams. I wanted an even number to start with.

Phew, all done. Hope some found this interesting. Now I am off to bed, it is half past eleven, and I am sleepy. Take care, and see you later

 

[Zany_in_CO]

Hope some found this interesting.

Me! Me! Me! I did! Thanks for sharing!

170 grams = 5.1 oz.
140 grams = 4.9 oz.

 

[Kari Howie]

Great report, Bubble Agent! It will change my practice in that I will hold on to my soap a little longer before I give/sell it. Thanks for your research.

 

[AliOop]

Wow, this is amazing - I am surprised at how much water weight was lost. Since I use a 40% lye concentration for most of my batches, my guess is that my bars wouldn't lose quite that much over time. But even half of the weight loss you recorded would be more than I would have guessed. Goes to show that facts are better than guesses!

 

[ResolvableOwl]

Thank you so much for the verbosity, insights, data, and a smile!
I took the liberty to plot your weight history alongside the one of my (not quite as) long-term experiment, for a direct comparison. First off, you were more thorough in documenting the details of the drying/curing progress (how you prepared it “on point” a fixed starting weight, how you aerated it, etc.), so there is no absolute comparability (also the absolute weight is an inevitable source of uncertainty, because one can weigh a bar of soap only after unmoulding/cutting, but has it then already started to cure???).

The logarithmic axis might be a bit unusual for casual friends of happy point cloud pics, but it's the only sensible way to display the many close data points at the beginning, along the long-time trend, without distorting the graph in weird ways. Each subdivision is ten times the length of the previous one.

Weird enough, both soaps behave essentially identical. The steeper slope with your soap means it is losing weight at a slightly higher rate. I have the different lye concentration under suspicion: your 33% vs. my 39%.

Other than that, the mathematician in me is a bit unsettled that these are straight lines at all: in a semi-logarithmic diagram, a straight line means logarithmic relation between time and weight, i. e. the same weight loss in a time interval that is x times as long as the previous. No signs of a plateau, the speed of weight loss just diminishes – but there are no signs, neither with your nor my soap, that it drops fast enough that the soap wouldn't disappear in the far future! Fair enough, extrapolation is nonsense here (but if we do it anyway, it'll end up at 10 billion years, i. e. about twice as long as Earth exists as a planet – pretty sure that bar of soap will then be long gone in other ways.)


Anyhow, you mentioned that you intend to start performance testing on that bar. Great idea to judge the long-term performance – but how would you then keep track of the weight when you're washing off part of it? Or have I overlooked that you still have multiple bars from this batch around?
What I did was weighing the bar, split it in half, and note the weight of the “storage” piece. In my notes, I then multiply the further weights by the fraction of the storage piece weight with the whole bar, to “act as if” it would still be the large bar. This will alter the way of drying slightly (freshly exposed surface etc.) – but the alternative would be no lather tests …

 

[LynetteO]

@Bubble Agent Wow! I Science & my introduction an oil SAP changed my life in that after I “created” my 1st recipe & the soap was made… drop the I have a new hobby that I REALLY REALLY enjoy.
I concur with @ResolvableOwl in that your experiment experience is both well written & explained. Plus ancomparison chart addition . Nice!
Thank you both for sharing!!

 

[Carly B]

Me! Me! Me! I did! Thanks for sharing! View attachment 60305
170 grams = 5.1 oz.
140 grams = 4.9 oz.

I found it interesting, too, but my calculator says 170 gms is 5.9 oz., so it actually lost a full oz.

 

[ResolvableOwl]

170 g / (28.35 g/oz) = 5.996 oz
140 g / (28.35 g/oz) = 4.938 oz

I hope you Customary Units folks never come up with the idea to undertake really complicated things, like space travel.

 

[Zany_in_CO]

but my calculator says 170 gms is 5.9 oz., so it actually lost a full oz.

Oopsie! I stand corrected. TY.

 

[paradisi]

170 g / (28.35 g/oz) = 5.996 oz
140 g / (28.35 g/oz) = 4.938 oz

I hope you Customary Units folks never come up with the idea to undertake really complicated things, like space travel.

The problem there was mistaking which units the equipment was sending, not the units themselves. Metric isn't inherently more accurate.

If memory serves, most regulators recognize too that many products will experience some shrinkage due to their nature. Though labeling soap with cut weight, even in grams, would be a fail.

 

[ResolvableOwl]

Let me just be a bit snarky that it seems acceptable to round 5.996 oz to 5.9 oz, okay?

Of course, the precision of any system of measurements only depends on the data. If looked at without context, there is no “better” or “worse” unit system. But unit systems are not without context. That loss was not due to a flawed measurement, but flawed data management, not a metrology but an informatics issue. Everyone should be aware that some kind of informatics is happening in every cookbook and on every quickly scribbled soap recipe. Unit systems don't replace diligence.

 

[Quilter99755]

I love it! For some reason a couple years back I made three batches of soap, which I set aside one bar of each and measured them at intervals. In the middle of my experiment, my daughter's garage burned and left her house unlivable so she, grandson and two dogs moved in with us. We live in a nice house that fits us two old people and adding kids and dogs made any continued data impossible. I was lucky to still have room for my soap storage let alone collect data.

So this is doing exactly what I was tracking...although yours is a bit different in scope it is still giving me information that I wanted to track...without finishing my experiment. Thank you so much for posting...and all the details. Here's hoping that I can start over and share mine someday!

 

[Bubble Agent]

I apologize if I confused everyone using gram weights instead of writing down the oz weight. But working with such minute changes at a time I wanted to make sure I didn`t goof up the numbers, as we only use the metric system here in Norway when it comes to measuring weight.

Me! Me! Me! I did! Thanks for sharing! View attachment 60305
170 grams = 5.1 oz.
140 grams = 4.9 oz.

Thank you popping in, Zany, so happy to hear you enjoyed my rambles

Great report, Bubble Agent! It will change my practice in that I will hold on to my soap a little longer before I give/sell it. Thanks for your research.

Thank you! And so happy you could find something usefull in my little experiment

Wow, this is amazing - I am surprised at how much water weight was lost. Since I use a 40% lye concentration for most of my batches, my guess is that my bars wouldn't lose quite that much over time. But even half of the weight loss you recorded would be more than I would have guessed. Goes to show that facts are better than guesses!

So true, facts before guesses is the way to go, which is a good principle to live by in general. At least where it is applicable

I have made a coupple of soaps with 40% instead of 33% lye concentration, that was a long time ago, and as far as I can remember it is true that the waterloss is different. They didn`t shrink quite the same way. But I haven`t actually recorded that type of data like this. It was just a couple of tests anyway, as it seems 33 is my general sweetspot. I have some accelerating fragrances that is manageable with 33%, and with a CPSR I have to keep using the same ratios every time, so 33% was the best middle ground I landed on. (I can play around and do whatever I`d like with my personal soaps of course)

Thank you so much for the verbosity, insights, data, and a smile!
I took the liberty to plot your weight history alongside the one of my (not quite as) long-term experiment, for a direct comparison.

Anyhow, you mentioned that you intend to start performance testing on that bar. Great idea to judge the long-term performance – but how would you then keep track of the weight when you're washing off part of it? Or have I overlooked that you still have multiple bars from this batch around?

Well, if bees had knees, those data would have been it! What a fun chart, thank you for doing that!! As mentioned I am not a mathematician, and a lot of stuff just wooshes over my head, so thank you for explaining what a straight line means when it comes to the logarithmics!

Sorry, I probably wasn`t really clear on what I meant. What I am going to do is saving this bar for 5 more years, just keep measuring it, but not using it.

When it reaches the 7 year mark (if I live that long, lol) I will then stop measuring the weight completely (as I just decided that 7 years will be the cut-off).
Then I will cut the soap in 3 parts and use 1 or 2 parts over the upcoming years as comparison.

I know you didn`t ask about this, but you may wonder why I am not simply using the whole soap bar as is after those 5 years when weighing has passed.

But the reason is that I want to see how the parts that I am NOT exposing to light, water and general air - how they behave without being used.

If I use the whole bar for testing, I just feel like I will lose some data on how it will fare (dos, shrinkage, fragrance, color etc) If I keep adding water and sudsing up the whole soap it will be altered for each use.
OK, I am not sure if this is the correct word to use, "altered", but hope you know what I try to convey

@Bubble Agent Wow! I Science & my introduction an oil SAP changed my life in that after I “created” my 1st recipe & the soap was made… drop the I have a new hobby that I REALLY REALLY enjoy.
I concur with @ResolvableOwl in that your experiment experience is both well written & explained. Plus ancomparison chart addition . Nice!
Thank you both for sharing!!

Thank you, Lynette, for popping in and share this! I wasn`t really expecting anyone really care about this, as I just did it for a nerdy experiment for myself. But I should have known, I mean, soap + soapmakingforum= fellow nerds soapers

I found it interesting, too, but my calculator says 170 gms is 5.9 oz., so it actually lost a full oz.

Thanks for clearing that up, Carly

170 g / (28.35 g/oz) = 5.996 oz
140 g / (28.35 g/oz) = 4.938 oz

I hope you Customary Units folks never come up with the idea to undertake really complicated things, like space travel.

I had to click. And wowsah...

 

[Bubble Agent]

I love it! For some reason a couple years back I made three batches of soap, which I set aside one bar of each and measured them at intervals. In the middle of my experiment, my daughter's garage burned and left her house unlivable so she, grandson and two dogs moved in with us. We live in a nice house that fits us two old people and adding kids and dogs made any continued data impossible. I was lucky to still have room for my soap storage let alone collect data.

So this is doing exactly what I was tracking...although yours is a bit different in scope it is still giving me information that I wanted to track...without finishing my experiment. Thank you so much for posting...and all the details. Here's hoping that I can start over and share mine someday!

Oh dear, sorry to hear about the fire, and what happened! I can imagine a situation like that made your efforts difficult to continue for sure. I am happy to hear that you could at least extrapolate something out of my data, and the great work of @ResolvableOwl !

Although I do understand of course that it isn`t the same as doing your own, but as long as you have some soap it is not to late to start a new experiment. And perhaps you will be more diligent than I have been, and do it in an even better way. I will look forward to your findings, whenever they may occur

If memory serves, most regulators recognize too that many products will experience some shrinkage due to their nature. Though labeling soap with cut weight, even in grams, would be a fail.

Yes, that is why I am obligated by regulations to use the estimated sign, or the e-mark after the final weight of my cured soap, on my packaging (net weight).

Even automated packaging machines in the food industry are not completely accurate, and there will be a tiny margin of inaccuracy. The same margin I am allowed to have, as per regulations.

Btw, I would never ever lable my soap with cut weight, that would be so totally dishonest.
Do even people do that?

 

[ResolvableOwl]

I apologize if I confused everyone using gram weights instead of writing down the oz weight.

Don't make it too easy for “them” . No, joke aside, it really doesn't make a difference. Especially the conversion hassle completely disappears with this thought experiment: if one takes gram weighs, and scale them down by 28.35, one has the numbers in oz. BUT one could as well scale up the batch itself, i. e. not just make one test bar, but 28⅓-ish identical test bars, and let them cure side by side – then the weight of one in g is equal to the weight of all together, but in oz.
Conversion factors in both unit-conversion-on-paper nor batch-scale-up just cancel out (that's math), batch size doesn't change the amount of water loss per some arbitrary, but fixed quantity of soap bar (that's the physics).

That's why it is most natural (plus unit-system agnostic!) to give weight in % of the initial weight.

 

[Bubble Agent]

Don't make it too easy for “them” . No, joke aside, it really doesn't make a difference. Especially the conversion hassle completely disappears with this thought experiment: if one takes gram weighs, and scale them down by 28.35, one has the numbers in oz. BUT one could as well scale up the batch itself, i. e. not just make one test bar, but 28⅓-ish identical test bars, and let them cure side by side – then the weight of one in g is equal to the weight of all together, but in oz.
Conversion factors in both unit-conversion-on-paper nor batch-scale-up just cancel out (that's math), batch size doesn't change the amount of water loss per some arbitrary, but fixed quantity of soap bar (that's the physics).

That's why it is most natural (plus unit-system agnostic!) to give weight in % of the initial weight.

Wow, that was cool math. Mind. Blown.

28⅓-ish --- I`m dying

Thanks for explaining that math. Very cool! I can`t promise I`ll remember this forever, but at least it is nice to not have that woosh-sound hovering over my head today...

 

[Rsapienza]

At one time I was obsessed with soap making (as I’m sure y’all understand). Problem was I had hardly anyone to give it to and was not selling. Needless to say, many batches stayed around for long periods of time. I had set aside several bars over the years and weighed at different intervals and found that they never stopped losing weight.
i remember reading something DeeAnna had posted about soap always having liquid inside (or something along those lines). If I’m not mistaken, it was compared to liquid in a slice of bread, (please do not quote me), and that some things always have a liquid structure in them. I actually posted something in a FB group a few years ago about soap never ceasing to lose weight, IME, and I was quickly shot down by a very well known soap maker saying that I was wrong and that any fluctuation in weight had to do with the humidity in the air or something like that. I never responded, but I am absolutely positive that my soaps continue to lose weight beyond 2 years, and they never go up in weight….only down. I live in Florida where a/c is pretty much a constant. My humidity stays relatively the same indoors.