Calculating final water and natural glycerine amounts

[Andrea]

Hello

So I've received my safety assessment and reviewing it and on one of the pages shows what the maximum level of water and glycerine allowed in the final product are.

I was wondering how I would go about calculating how much water IS left in my soap post-curing and how I would know how much natural glycerine was created during the cp process?

 

[Relle]

Here is a previous thread about the glycerine calculation
http://www.soapmakingforum.com/showthread.php?t=30304

 

[soap_rat]

I'm very curious about the water content myself, I hope someone knows about that.

 

[Lin]

You can compare the weight loss of the soap to the weight of water used to find out the difference, and then how much water is left. If you've used a water swap you'll have to determine the amount of water in your liquid first though.

 

[Seawolfe]

Since it asks for the MAXIMUM amount of water in your product, isn't that the original amount?

 

[DeeAnna]

The OP asked: "...how much water IS left in my soap post-curing..."

The answer you are suggesting is a pre-cure moisture content, SeaWolfe. Lin's answer is correct for post-cure.

Here is an example for two of my soaps. The results for these two are similar, but the recipes use the same lye solution concentration. If your solution concentration is different between any two soaps, the final moisture content will likely be different too.

I'm not in the EU/UK/Canada, however, so maybe there's a handy dandy estimator that folks can use instead of taking actual the measurements like I did.

 

[DeeAnna]

"...how I would go about calculating how much water IS left in my soap post-curing..."

The initial recipe will give you the initial water content of the soap. Using one of my soap recipes as an example, the final weight of all ingredients is 2456 g. Of that, 423 g is water. So the water content of an ideal bar pre-cure is:

423 / 2456 * 100 = 17.2% water in the soap
Another way of saying this is there are 17.2 g of water in every 100 g of soap.

Next step is to find the post-cure weight of the soap. Using the information from my test (chart in my previous post), a bar will weigh about 91.5% of its original weight after 50 days of curing. So a 150 g bar would end up at 137 g. This weight loss is mostly or all water. Assuming it's all water, how much water is lost?

Starting weight - Ending weight = Water lost
150 - 137 = 13 g water lost in 150 g of soap

That's 13 g lost from 150 g of soap. I want to get this on a consistent basis of "100 g of soap", so I have to do a dreaded ratio problem:
13 * 100 / 150 = 8.7 g water lost in every 100 g of soap

So now I know the water LOST from the soap during the cure. But I really want to know the water that's STILL IN the soap. Use the numbers based on "100 g of soap" to find the answer:

Starting water - Water lost = Ending water
17.2 - 8.7 = 8.5 g water in every 100 g of soap post-cure

This answer is the same as a percentage, so the percentage water in this soap post-cure is 8.5% give or take a bit.

The actual numbers are true for this one particular soap. The answers will likely be somewhat different for another soap, but the method would be the same.

I hope this helps!

 

[MzMolly65]

"...how I would go about calculating how much water IS left in my soap post-curing..."

Newbie questions .. WHY? would I need or want to know this information?

 

[The Efficacious Gentleman]

Because if you are selling soap, the recipe can only have a certain water ratio. Go over that and you are very naughty indeed.

Out of interest, OP, what is the maximum amount you are allowed in this case? If it's not too far off of your starting water amount then there isn't much point worrying

 

[MzMolly65]

Because if you are selling soap, the recipe can only have a certain water ratio. Go over that and you are very naughty indeed.

Thanks Gent .. is this a world wide requirement or an EU requirement?

 

[The Efficacious Gentleman]

Knowing how they are here in the EU, most likely just here! I think in the US the labels are much lighter in the requirements

 

[seven]

Because if you are selling soap, the recipe can only have a certain water ratio. Go over that and you are very naughty indeed.

seriously? there is a rule in the EU about how much water you can have? zomg! what is the point? and what is the maximum?

you don't have to write about water ratio on your labels do you?

 

[FlybyStardancer]

Maybe it's there to prevent sellers from selling their bars as, say, 5oz bars, but then having the soaps lose an ounce of water before the customers use it? (Is just guessing here.)

 

[DeeAnna]

In the mid 1800s in the UK (and most likely elsewhere), there were apparently laws that tightly controlled the adulteration of soap, complete with taxes, penalties, and inspectors. One of the old soapmaking manuals I've been reading recently has an intriguing little soliloquy on the politics of soap making of the time. It was perfectly clear he despised the soap inspectors and what he perceived as their arrogant attitude.

My impression is the laws were relaxed or lifted around the turn of the century and adding "fillers" became an important aspect of making soap. Soaps were filled with chalk, salt, rosin, excess water, and just about anything else that would add cheap bulk to the soap and was reasonably safe. Why? Some fillers are helpful additives -- for example, rosin adds cleaning power to household and laundry soaps and pumice is helpful for cleaning greasy dirt.

In many other cases, it was all about economics and survival. As now, there was a lot of competition for market share back then. One way to survive is to reduce the cost of your product by adding inexpensive fillers. I think the race to cut costs got really out of hand to the point that consumers rebelled and soapmakers lost a lot of credibility. In some of the old books, the authors talk about getting soap sold quickly -- they wanted to get it in consumers' hands before the soap shrunk and distorted and changed color enough to look bad. Yikes!

Perhaps in tight control over soapmaking in the EU and elsewhere comes partly from this history -- but that's just my guess.

I think it could be argued that some of the additives put into today's handcrafted soap are unnecessary fillers. Food purees and salt come to mind. Maybe the soap makers don't see it that way, but perhaps consumers might see it differently.

 

[Lin]

What book is it? Do you think food purees are unnecessary fillers? Curious, because in that case they actually increase rather than decrease the cost of producing the soap lol.

I'm reading a book right now thats more aimed to commercial soap producers, and I found the section on Rosin interesting. The author was arguing against people considering it to be an adulterant since it saponifies and ads its own cleaning properties to the soap. Defended its use in both laundry and toilet soaps. But it did discuss how Rosin used to be an incredibly cheap ingredient, but now it can actually raise the price of the soap production to include it.

 

[The Efficacious Gentleman]

What book is it? Do you think food purees are unnecessary fillers? Curious, because in that case they actually increase rather than decrease the cost of producing the soap lol.........

I can get 1 kilo of carrots for 1€ - I can't get a kilo of any oil for that price! Could certainly be used to fill up.

I'm not saying it is, though.

 

[DeeAnna]

Hey, Lin -- It's Alexander Watt, The art of soap-making, 1884. Think I got it from the Internet Archive. HTH. --D

Oh, forgot:

"... Do you think food purees are unnecessary fillers? Curious, because in that case they actually increase rather than decrease the cost of producing the soap lol. ..."

I can see it two ways --

If a consumer wants to use soap to clean the body, and if food puree does not actually do anything to specifically clean the skin, then, yes, for that consumer the food puree would be a filler that reduces the intrinsic value of the soap to that person. I agree it's not a filler to reduce costs as was done in the 1800s, but the puree is not adding value to someone who views soap ... as just a way to get clean.

Other consumers might like a soap with food puree because they might view the puree as interesting, adventurous, romantic, "skin nourishing", or whatever. And if that is how they view a soap, then the puree is a value-added ingredient and all's fine.

 

[Lin]

I can get 1 kilo of carrots for 1€ - I can't get a kilo of any oil for that price! Could certainly be used to fill up.

I'm not saying it is, though.

I don't know of anyone substituting puree for oil, its substituted for water (or just added in additionally to water) in which case it increases the price of the soap over one using water.

Is there carrot oil in carrot puree? lol. You'd need a whole lot of puree before you could compare it to purchase prices of oils.

 

[AnnaMarie]

Okay, I just stumbled onto this interesting thread. Would someone be able to explain to me why there is a maximum on glycerine in soap? I thought glycerine was beneficial to skin, so I'm wondering if I'm wrong or what??
Cheers!
Anna Marie

 

[The Efficacious Gentleman]

I don't know of anyone substituting puree for oil, its substituted for water (or just added in additionally to water) in which case it increases the price of the soap over one using water.

Is there carrot oil in carrot puree? lol. You'd need a whole lot of puree before you could compare it to purchase prices of oils.

When talking of a filler in this instance, it's of course going to be replacing oils (expensive) in the total weight of the finished product - you want to make a 4 oz bar but on the cheap? Use more water-replacement puree so that the final weight is higher than it would have been if the normal water amount was used. You get a 4 oz bar but with less oils used - it has less soap and more 'water' than it should have.

We're talking about how people tricked the weight of their soaps in the old days, not what people use purees for now.