lye solution/concentration vs. water as % of oils

I've searched the forum and read quite a few threads on the difference between a lye concentration (or solution) and water as % of oils when calculating the amount of water to use. I have a clear understanding of the difference, and I see that most people prefer to use the lye solution method. That's what I've been doing, too, but I'm starting to question it.

I understand how the solution method makes more sense if you want your water:lye relationship to be consistent between recipes, and obviously you want to make sure you're using enough water for your lye to be sufficiently dissolved.

But as long as your lye is sufficiently dissolved, and as long as your solution strength is not problematic for your recipe in terms of trace time, etc., why is it preferable to have your water:lye ratio be consistent from batch to batch, instead having your water: oils ratio be consistent? I'm thinking in terms of the water that evaporates while the soap cures. Wouldn't the amount of water that your soap has to lose be more consistent between recipes if it were based on the weight of oils, rather than the lye solution strength?

I read this: http://rivercitysoaps.com/dwcp/dwcp.pdf, and it said that using the weight of oils to calculate your water can result in your solution strength varying widely between batches. But why is that any worse than having variable amounts of water weight that need to be lost while curing?

I'm sure there's a good reason for this, since so many the experienced soapers on the forum prefer the lye solution method. But I'm the type who doesn't only want to know which approach is the best. . .I want to know WHY it's the best!

Jane, did you scroll down to read page 3 of the River City PDF? To me, that page says it all.


IrishLass

As you noted, using "water as % of oils" causes the water amount to vary, depending on the saponification value of the oils. A recipe using "water as % of oils" will have a less concentrated lye solution when using fats with lower sap values (say olive) and a more concentrated lye solution for fats with higher sap values (say coconut).

This is exactly the opposite of what you might want.

For example, olive oil saponifies slowly -- sometimes too slowly -- when made with a more dilute lye solution. It does best with a moderate or even a more concentrated lye solution. Coconut oil saponifies quickly and easily, so it may be desirable to use more water with a recipe high in coconut oil. More water will slow down saponification so you can have more time to swirl and to minimize the chance of overheating in the mold.

Your focus appears to be on what happens after the soap is made, but a person has to consider what happens during saponification too.

IrishLass said:

Jane, did you scroll down to read page 3 of the River City PDF? To me, that page says it all.


IrishLass

Click to expand...

I did! Are you thinking of the part that says: "Let’s look at it another way: Since water can dissolve its own weight in lye, we need just under 13 ounces of water to dissolve the lye for the castile. If we use 38 ounces, we have almost three times as much water as needed. No wonder castile soap takes so long to cure!"

I can see why that would be problematic.

DeeAnna said:

As you noted, using "water as % of oils" causes the water amount to vary, depending on the saponification value of the oils. A recipe using "water as % of oils" will have a less concentrated lye solution when using fats with lower sap values (say olive) and a more concentrated lye solution for fats with higher sap values (say coconut).

This is exactly the opposite of what you might want. For example, olive oil saponifies slowly with a more dilute lye solution. It does best with a moderate or even a more concentrated lye solution. Coconut oil needs no help to saponify quickly, so it may be desirable to have more water with a high CO recipe to have more working time and to minimize overheating.

Your focus appears to be on what happens after the soap is made, but a person has to consider what happens during saponification too.

Click to expand...

. . .and there goes the lightbulb. Thank you!

Ok, so now I'm wondering: why do big-name soapers like Anne-Marie do water as % of oils? Hers are very consistently 33% of oils. I'll search her blog, but I'm not sure I've ever read her explanation.

And why would SoapCalc, which is built for highly-customized recipe planning, default to water as % of oils, when that's far less tailored to your recipe?

That approach to water seems inconsistent with their approaches to everything else.

I tend to pay attention to both, although my water as percent of oil weight tends to sit around 25% (with a 33% solution strength).

However, if I'm planning on a complex swirl, up goes the water amount. Lots of olive in a single color? Down goes the water amount. Other variables, like oil temperature, also vary by how much work time I'm going to require.

My primary consideration is that I have the time to create the design I envisioned.

Cutting time will need to adjust. A three layer soap I just made was higher water to give me ample work time, so it was just taken out of the mold Friday, after 2 days to solidify and saponify. I may end up cutting this evening, or it may have to wait a bit longer. That's no problem, I can keep the log in my work area until it's ready.

I'll pick up any difference during cure, as soap with higher water tends to initially lose more water weight anyway. And if it takes an extra week to complete cure, I don't care.

"...Ok, so now I'm wondering: why do big-name soapers like Anne-Marie do water as % of oils? Hers are very consistently 33% of oils...."

I'd guess that's how Anne-Marie learned to soap, and she has no reason to change a strategy that works fine. My background is in chemistry and engineering, so my perspective is probably different than hers. It gives me the heebie jeebies to use "water as % of oils". I don't like it that my water content might change as I alter the blend of fats in a recipe -- especially since the change will be opposite to what will work best for the soap.

And I am guessing the bias in SoapCalc to use "water as % of oils" is because the owner perceives this to be the most common way people set up recipes. Just a guess though. Whether this bias is really the best way to design a soap recipe is another story.

As was pointed out in another thread, saying x cups of oils and y cups of lye can be "safe" but far from ideal. Water as % of oils works for making soaps, but the two other options can often allow more control.

ETA - a lot of the "big soapers" are also of course aiming at the larger audience, so need to use something (dare I say) basic that everyone can grasp.

Also Ann Marie's focus is supplies, not soapmaking...

is "water as % of oils" such a bad thing ? [that's what i cut my teeth on and tend to stick to it ] . i get the "water : lye ratio" , seeing that lye needs its own weight in water to properly dilute, putting 2:1 as a safe ratio. what i am trying to wrap my head around is how "lye concentration " any different than "water as a % of oils" , seeing that you can set the percentage...or is the two percentages affecting different things [ say if i set water as a % of oils to say 33% is it something totally different to setting lye concentration to 33% ? ]

also, doesn't your soap still require 4-6 weeks to cure no matter which one you chose to work with ? i get that less water means less "drying " time and less shrinkage but still more time curing makes for a mature soap...... so where did i fall off ?

You are right -- no matter how you figure out the water for a recipe, the finished soap needs to cure properly.

***

The first two images are examples of why "water as % of oils" gives variable results in soap making. I used Soapcalc to figure a 100% lard soap and a 100% coconut oil soap. I left the default setting of 38% water as % of oils for both recipes. Let's see what the lye concentration is with these two examples. I've rounded everything to whole numbers, just to keep things simple.

In the 100% lard example, the lye solution concentration is 67 / (190 + 67) = 26%. This is almost too much water for CP -- it's more like an HP recipe. Sometimes new soapers complain that their soap takes forever to trace or stays overly soft or even separates in the mold. Too much water can be one of the reasons why.

In the 100% coconut oil example, the water is the same weight, but the solution concentration is quite different. It's 87 / (190 + 87) = 31%. That's quite a bit more concentrated. Many people complain that coconut oil soap overheats easily. Using "water as % of oils" can easily trigger overheating when making a soap that's high in coconut oil.

For those newbies who are scared of higher lye concentrations but are thinking about tackling an 100% CO laundry soap, this should be an eye opener!

***

The next two images are the same recipes, except I used a consistent lye concentration of 30% for these recipes. I could have used the lye:water ratio if I wanted -- it's just another way of saying the same thing. I just think it's easier to think about percentages than ratios when doing this kind of thing.

In the second 100% lard example, the lye solution concentration is 67 / (156 + 67) = 30%. In the second 100% coconut oil example, the solution concentration is 87 / (203 + 87) = 30%.

No surprise that the lye concentration is the same in both of these examples. That's what I'm looking for when I use lye concentration -- I want consistency from recipe to recipe.

Since I know coconut oil soap tends to trace fast and possibly overheat in the mold, I can use the lye concentration setting to compensate for this tendency -- maybe I want to use a 28% lye concentration for the coconut oil recipe instead of 30%.

Regardless of my decision on the matter, my control of this is going to be consistent and reliable from recipe to recipe only if I use lye concentration rather than "water as % of oils".

***

What I'm trying to say here is that you can use "water as % of oils" if you only make minor changes to a recipe and you will get reasonably consistent results if you aren't too adventurous.

On the other hand, your results using "water as % of oils" might be more variable than you'd like if you like to make a wide variety of recipes. It's my opinion that using lye concentration will give more consistent results from batch to batch. You are less likely to see the instant trace and overheating surprises with your high CO recipes. You also won't get high lard or olive oil batches that take ages to trace and even separate in the mold.

***

Here's the bottom line:

The amount of lye in proportion to the fats is the key thing that ensures the soap will not be lye heavy. Soapcalc will always give you the proper total weight of lye for the fats in your recipe.

It is not important to control the amount of water in proportion to the fats. It's the amount of water in proportion to the lye that is critical. You can only get that consistency if you use lye concentration or water:lye ratio, NOT "water as % of oils".

I want to add this metaphor to explain my point in a different way --

Saponification is like a big party. At this party, there are guys (lye molecules), there are girls (fat molecules), and there are varying numbers of chaperones (water molecules). Chaperones are present to keep the guys in line, but the numbers of chaperones can vary, since some girls will do their own chaperoning.

If the girls are modest young women raised in a strict Victorian tradition, not a lot of chaperones are needed to keep the party well behaved. This situation is like the olive oil soap I talked about above. Olive oil does not care to saponify quickly, so it behaves in a "modest" kind of way. If you use lye concentration to determine the chaperonage needed, you could have just 1 or 2 chaperones (water) per guy (lye) and the result will be sparkling conversation and plenty of dancing. If you use "water as % of oils", however, you will get 3 or 4 chaperones per guy, and the party will be as dull as dishwater.

If the girls are (ahem!) modern young women who are somewhat less restrained than their Victorian sisters, more chaperonage is needed. Sometimes a LOT more. This situation is like a coconut oil soap. CO is quite happy to saponify easily, so it behaves in a rather "fast" way. If you use lye concentration to determine the chaperonage, you might choose to have 3 or 4 chaperones (water) per guy (lye) to keep the party under control. If you use "water as % of oils", you will get only 1 or 2 chaperones per guy, and that will result in an out-of-control crazy party likely to end with a police bust.

I hope you can see by this party metaphor that the using "water as % of oils" provides too many chaperones (water molecules) at a saponification party when fewer would be better, and vice versa. Only when you use "lye concentration" can you choose the right amount of chaperonage to help the saponification party stay fun yet under reasonable control.

[For another saponification party story, see http://www.soapmakingforum.com/showthread.php?t=52034&page=2 Post #12.]

Trying to wrap my head around all of this and it's not clicking. I'll try to read it all again and comprehend.

I think I got it:

Water as % of oils is the same as saying chaperons per girl because in our example, water is the chaperons and oils are the girls. But we don't need the chaperons to look after the girls. Yes, the number of girls loosely corresponds with the number of boys, so we'll be about right, but it's still not the right way to do it.

We want to control the number of chaperons per boy, not per girl. So instead of water as % of oils, we use water as % of lye or, in other words, lye concentration.

Yes, that's it in a nutshell. Good summary NAPD -- thank you!

I just re-read this thread and it has me thinking about an issue I had in my first couple years of soaping and before I started soaping. Back then I thought olive oil was great and used around 30%-40%, with the soap calc water default because I was afraid of discounting. It I did water discount or at least I thought I was, I would only lower the number down to 35%, which was before I joined this forum. Before that I self taught, no you tube, no forums just a small book from B&B, by the way I still have my first lard soap made with Snow Cap lard. I kept running into overheating and separation problems when I would gel my soap, which I still thought I had to do. Once I joined here I learned I did not have to let my soap gel and put them in the freezer. Back to the point, I learned here about how full water will cause more heat, makes sense after thinking about it, and higher water with higher OO can cause separation. By then I was actually deciding I really did not like OO over 20% so stopped using the higher amounts and started using the soap calculator water in oil at 32 ( big whoop ). Now my standard is the same as IL, a 33% lye concentration which is adjusted per recipe and/or fragrance. The only time I have had overheating is with cranky heating up fo's

Ok, I took that pdf from the first page to bed last night and I now grok what the reasons are and the differences are. What I can't wrap my head around are the calculations on page 4, the Formulas for DWCP, Calculating water for commonly used solutions. Where did the initial:

lye weight x 2.33 = water for a 30% solution
lye weight x 2.23 = water for a 31% solution
etc.

Where did the 2.33, 2.23, 2.13, 2.03, etc. come from?

Sorry to be so dense......

Water weight = (Lye weight) X (Water percent) / (Lye percent)

In a 30% lye solution, 30% is lye. The water has to make up the rest of the solution to equal 100%. That means the percent of water in the lye solution is 100 - 30 = 70%. So the other bit of information needed is this: Water percent = 100% - (Lye percent)

Example: I want to make a 30% lye solution. My soap calculator tells me I need 120 g of lye. How much water should I measure out?
Water weight = (120 g lye) X (70/30) = 280 g

The ratio of 70/30 is always the same for a 30% lye solution so you can simplify that division problem to a decimal number: 70/30 = 2.33

For a 31% lye solution, the water percentage is 100 - 31 = 69%. The ratio of water percent divided by lye percent is 69/31 = 2.23
For a 32% lye solution, the ratio is 68/32 = 2.13
For a 33% lye solution, the ratio is 67/33 = 2.03
and so on.

I made coffee bars last night and set the lye concentration to 29%. I scooped 2 tablespoons of coffee powder instead of 2 teaspoon. Dang.

Perfect, thank you for tying the whole thing together, DeeAnna