Lye Concentration vs Water as a % of oils

Ok.. so on my question about the SM3 program I ran across the problem about how to go from my use of the 'water as a % of oils' on soapcal for discounting water, to the lye concentration for it. SM3 doesn't have the '% of oils' and I nor Sistrum could wrap our heads around how these two relate so they can be converted. Does that make sense? I'm almost confusing myself again thinking about it. roblem:

I was looking at Castile recipes and noticed Hazel mentioned using the Lye concentration.. is this what many of you use? Sistrum also said most who use SM3 use this but I always here about the 'water discount'.
Just when I thought I was doing good I'm confused again. LOL!

Hope I worded that right to get my point/question across on where I need clarification.

DeeAnna.. you on here? I know you seem to have the chemistry stuff down and understandable.

So glad you asked this question Jennee ( wink ). I know we aren't the only ones with this problem. I've seen a lot of posts where new soapers ask questions and state the lye they used as percent of oils and I know I'm not the only "old school" soaper that has a bit of a time trying to figue out how to answer correctly. A conversion chart or quick lesson would be great help.

Lye concentration refers to the ratio of water to lye.

A 50% lye concentration is equal amounts of water to lye so a 1:1 ratio of each. This is the most concentrated solution you can use at room temperature and still have the lye dissolve completely.

A 33% lye solution is roughly a 2:1 ratio of water to lye. So if you used 3 ounces of lye to 6 ounces of water, the % of lye in the solution would be about 1/3. This is what I use in my own soaping as a nice compromise between full water and pushing the envelope of what's possible.

Hope this makes sense. I never could figure out the logic of the water as % of oils myself. Lye concentration makes a lot more sense to me.

By the way, the standard 38% of water to oils is about a 25% lye solution on soapcalc, assuming a 5% lye discount (superfat).

Mmmmm. I can crunch the numbers for you, but gimme a little bit. Real Life is intruding on my soaping time more than usual today!

Oh, okay, found the spreadsheet I was looking for -- that saved me a little time.

At 0% superfat, the translation between the "% NaOH in water" and "water as % of oils" looks like this:

NaOH % in water **** Water as % of total oil
28% **** 40%
30% **** 37%
33% **** 32%
40% **** 24%
45% **** 19%
50% **** 16%

At 5% superfat, the numbers are:

NaOH % in water **** Water as % of total oil
28% **** 38% (aka "full water")
30% **** 35%
33% **** 30%
40% **** 22%
45% **** 18%
50% **** 15%

At 10% superfat, the numbers look like this:

NaOH % in water **** Water as % of total oil
28% **** 36%
30% **** 33%
33% **** 29%
40% **** 21%
45% **** 17%
50% **** 14%

I hope this helps.

I have read in various soap making books that 38% water as % of total oil was "full water" and that makes a 27-28% NaOH solution. These specific numbers appear to be based on a 5% superfat.

I'll stick with the "NaOH % in water" numbers, thankyouverymuch. Makes much, much more sense to me.

Yay! Thank you thank you.
I don't know why or how I started using the water to oil.
Guess ill be switching.
And now I can finally input my 40 or so recipes and understand what I'm doing when I'm using 'lye concentration'.

Much appreciated!

Thank you DeeAnna, I could never get that water as percent of oil thing. Personally I think it's one of the xxxxxxxxxxx. Especially if it changes with the super fat. No wonder people get confused!

DeeAnna - is there a formula behind the numbers? I would like to fiddle with it a bit on on paper before I put it into practice with actual materials. I'm not entirely sure why the switching between the two systems is so confusing to me.

And from the past


Exactly what Deda said. I don't calculate my water amount based on the oils either. I base it on my lye amount (using a 33% lye solution, normally). Here is a lye solution strength chart:


Solution Strength chart
Lye x 1.0 = 50% lye solution (the absolute limit; not recommended, esp. for newbies)
Lye x 1.15= 46.5% lye solution
Lye x 1.2 = 45.45% lye solution
Lye x 1.25= 44.44% lye solution
Lye x 1.3 = 43% lye solution
Lye x 1.4 = 41.66% lye solution
Lye x 1.5 = 40% lye solution
Lye x 1.6 = 38% lye solution
Lye x 1.7 = 37% lye solution
Lye x 1.75= 36% lye solution
Lye x 1.8 = 35.7% lye solution
Lye x 1.9 = 34.5% lye solution
Lye x 2 = 33% lye solution (a very good, general lye solution amount; my fave)
Lye x 2.1 = 32% lye solution
Lye x 2.3 = 30% lye solution
Lye x 2.7 = 27% lye solution
Lye x 3.1 = 25% (considered a 'full water' amount by most lye calculators)

Basically, what this chart is saying is that if you want to use a 33% lye solution, for example, you would be adding twice as much water as lye.

I hope that helps!
IrishLass
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I still can't post links so this is cut and paste from old post.

So.. With a Castile I would normally want to do a water discount and put in 30% for the water as % of oil.. But now I leave that at 38 and change to 28 for lye concentration when using a 5% suoerfat. Is that right?

If I do 7% sf can I still leave the lye concentration at 28 and be ok?

I'm wondering if the superfat difference you gave we're just for converting one recipe to another like for SM3?

Think I'm still a tad confused. Haha!
Started working on Castile and realized this info I'm not clear on.

You don't need to calculate the SF if you're working with lye concentation as opposed to water as % of oils.

For Castille, I'd recommend a lye solution of 33-40%, irrespective of SF.

Am I glad others mentioned that water to lye %'s make more sense to them than oil to water. For me, I understand you need so much water to dissolve the lye, and enough to work with the oils once you put the lye solution in. Those are things I think about when making a recipe-- not my oil to water %'s. To me I just think about the liquid that will eventually evaporate from the batch once the soap has cured. Or at least that is the only nod of thought I give to the balance of water to oils-- except when it comes to fast moving oils.

First come the oils. Then, dependig on the amount and the type of oils, comes the lye. Then, depending on the aount of lye, comes the water.
So, I use in SoapCalc oane of these two option:
Lye concentration (usualy 33.33%)
or Water : Lye Ratio (usualy 2:1)

(33.33% Lye concentration or 2:1 Water:Lye Ratio is the same thing)

Like Judy said you probably don't want to use full water for a 100% OO soap. So on SM3 Putin your oil amount then hit the lye/water tab put in what ever you want your superfat then click the "lye solution" button and put in 33 or what ever strength you want to use. The water discount box will change so you can see what it says but it most likely it wont be the same amount that "soap calc" would say. Is that what you were asking?

"...DeeAnna - is there a formula behind the numbers? ... I'm not entirely sure why the switching between the two systems is so confusing to me...."

Because it IS confusing, even to me, and I'm pretty comfortable with math.

I was rushed this morning and didn't think it all through before I sent off my reply. The conversion is not only affected by superfat, as I mentioned earlier, but also by the fats in your recipe. This morning, I used a recipe that was 60:40 lard and coconut oil to crunch the numbers. If I use a different recipe with a different overall saponification value, the conversion from "water as % of oils" to "NaOH solution concentration" is slightly different. Ugh.

But it can be done. The easiest route is to convert a recipe from "water as % of oils" to "NaOH solution concentration". So here's an example of how Jennee might convert one of her recipes:

1. Pick a recipe of any size and any blend of fats. Use ounces or grams, whichever works best for you. Just keep your units consistent -- don't use ounces for water and grams for NaOH for example. Use ounces and ounces or grams and grams. To keep the numbers simple, I'm going to choose 100 grams (100 ounces works too) of lard as my example recipe.

2. Figure out the NaOH required for your recipe and your desired superfat. You can get this value from SoapCalc or your favorite soap recipe calculator. For my example, I'm choosing 0% superfat. According to my soap recipe calculator, the lye required to saponify 100 g of lard at 0% superfat is 14 grams of NaOH.

3. Pick a "water as % of oils" number that you want to use. For my example, I'm choosing "full water" at 38%. Calculate the grams of water from the total oil in the recipe and this percentage. The math:

Remember -- if you want to do math with percents, you must first convert the percentage to a decimal number:
38% / 100% =
0.38

Calculate the water from the total oil weight multiplied by the "water as % of oils" decimal number:
100 grams of oil X 0.38 =
38 grams water

4. I now have numbers for my water (38 g), NaOH (14 g), and total fat (100 g). Calculate the NaOH solution concentration from the grams of NaOH and the grams of water. (Keep in mind the total amount of lye solution = NaOH weight + water weight). The math:

Figure the total amount of NaOH solution -- it's the sum of all ingredients in the solution (the NaOH plus the water):
14 g NaOH + 38 g water =
52 g

Figure the NaOH solution concentration by dividing the NaOH weight by the total weight of the solution:
14 g NaOH / 52 g solution =
0.269

Convert this fraction into a percentage:

0.269 X 100 =
26.9% NaOH solution concentration

Done!

It is possible to convert a recipe based on "NaOH solution concentration" back to a basis of "water as % of oils" but it requires more algebra than Jennee's route. If y'all want to go there, I will show you how, but I'll do it in another post. I don't want folks to give up by dosing y'all with too much math at one time.

wow, I'm I glad when I learned to make my own formulas it was just "add twice as much water as lye". And that was that!

( of course you did have to work out your lye amounts from the sap values you could find)

I agree, Sistrum. Converting a recipe from "water as % of oils" to solution concentration is a fair bit of work for not a whole lot of benefit. But some people get started with the "water as % of oils" and have to do a bit of a course correction, like Jennee. I'm glad to help out if so.

Solution concentration is the only way to go, IMO. It directly and clearly defines what a soap maker should really worry about -- the amount of lye and water in the lye-water solution. This "full water" and "water discount" and other odd terminology I stumble across sometimes -- all of that makes a big mystery out of soap recipe design. It is really a straightforward process, IMO.

Didn't you learn soap making from your Grams? If so, she was a smart gal to get you started the right way.

Thank you.
All I've learned in terms of soapcal was online and then askin questions here and another forum. Not sure if things were translated wrong to me or with me. Like maybe I misunderstood from the start. But they have that option in bold and guess I also thought that was the one to use. And then it says 'water' so when people say lower you water and use 35 or 25.. It seemed logical to use that one. :/. And I know somewhere I read or was told to change the '38' full water to a lower amount. I've always just stuck with it since I thought it was what all used and was easiest.

The other one does make sense and I would prefer it but didn't know numbers for it. Now I do!

My grandmother taught me to soap with her recipes but when I started to formulate on my own i just had to dig deeper and find out why things happen the way they do. If you have soaped for a long time you know there is away around the "rules" we use now. Grams way worked well when oils were limited but things are more consistent using the information we have access to now a days.
Like you and forum peeps. Lol

sistrum said:

wow, I'm I glad when I learned to make my own formulas it was just "add twice as much water as lye". And that was that!

Click to expand...

"twice as much water as lye" means 33.33% lye concentration or 2:1 water:lye ratio.