Superfats in recipes/posts: real or inaccurate due to lye quality?

[paragon]

When people post recipes or post about the soap they made, do they typically account for how fresh the lye is (old or improperly stored lye == lye discount) and give a really accurate SF%? Or do they assume the NaOH is pure? In other words, when someone writes "5% SF", for most people does that really mean 10% SF?

I ask because I bought a bag of fresh NaOH from my local chemical store, and they said it was dry. I stored it in an airtight box with chemical dehumidifiers. The soap I made with this new NaOH is all too drying, or at best borderline.

My soaps have typically been around 25% coconut oil. My first batch (also with 25% CO), which I made with super old lye, must have had a huge lye discount due to age, and it is quite good. Is the correct solution to use lower coconut oil or higher superfat?

Or to ask the simplest way: when someone says they like "5% superfat" on this forum, does that actually mean 10-15% unless it's written by a chemist type of person?

 

[Dawni]

I superfat my soaps always assuming that my lye isn't pure. How much is actually added on I have no idea.... Which I think a lot of us are aware of, but with no actual numbers to show.

But I formulate with very less coconut oil to begin with, hence my superfat is rarely even 5% (usually between 2-4) on the calculator. I've found its much harder to reach your conditioning goals and still keep the rest of the numbers where I like em. So instead, I lower my cleansing factor. I know a few others here do this as well.

Also, in my case, I always assume that I lose a little of the fats when I transfer containers. My pot is too heavy for my scale so I weigh my oils and butters separately then transfer into my slow cooker to warm.

So again, I have no real idea how much my actual superfat is but I don't think it's an additional 5% or more. There has been discussion on this before but I can't find them right now lol

 

[shunt2011]

You would have to know the purity of your lye to get as close to exact as possible. However, the lye we use isn’t 100% pure so there is a bit of difference in the accuracy of your SF. I SF at 3-6% depending on the recipe and additives. I use milks so that adds to the SF.

 

[paragon]

@Dawni You mean you usually have 2-4% SF on the lye calculator but you know it's actually higher?

@shunt2011 Do you mean estimated actual SF is 3-6% or that is before you account for lye impurity and water/CO₂ absorption during processing and storage?

Basically, I want to know if I should be adding 3-10% to every superfat percentage I read.

 

[Dawni]

@Dawni You mean you usually have 2-4% SF on the lye calculator but you know it's actually higher?

Yes. But never bothered to compute how much higher lol

Maybe I should......

I also know that the longer I have my lye sitting around since buying it (and not knowing how long it sat around before I bought it lol), the more superfatted the soaps are, compared to soaps made when lye was "new"

I hunted down a couple of links for ya.
https://www.soapmakingforum.com/threads/zero-percent-superfat.62504/#post-631804

https://www.soapmakingforum.com/threads/lye-purity-and-lye-aging.75174

None of these are the one I mentioned earlier haha but they explain a lol

 

[DeeAnna]

"...do they typically account for how fresh the lye is (old or improperly stored lye == lye discount) and give a really accurate SF%?..."

Most people do not adjust for purity because many soap makers do not know about this issue. One of the biggest reasons is most online soap recipe calculators assume the NaOH purity is 100% and don't give the user any option to enter a different purity. Most books and online tutorials about soap making also don't cover this aspect of soap making.

Most people never learn about the effects of alkali purity until they start making liquid soap with KOH (potassium hydroxide).

Furthermore, how is the average soap maker supposed to figure out what the purity really is? People can guess, certainly, but if they simply guess, they're still as much in the dark as if they assume the purity is 100%.

I give a quick-and-dirty method of checking alkali purity on my website and Kevin Dunn provides a more rigorous method in his book Scientific Soapmaking. While I think some people are curious about how the test is done, I would be surprised to see a lot of people doing the test. And to be honest, buying from a reputable supplier, knowing the supplier's stated purity, and storing the NaOH properly is plenty good enough.

A lot of NaOH (at least that sold in the US) direct from the suppliers seems to be around 95% to 97% pure. That creates a 3-5% hidden superfat fresh from the supplier.

"...I stored it in an airtight box with chemical dehumidifiers...."

Reading this at face value -- you mean you have solid NaOH directly in the same space with another desiccant? If so, please do not do this. NaOH is far more powerful than any other desiccant. The NaOH will strip water out of the other desiccant, lowering the NaOH purity.

Store the NaOH in its own air tight packaging. Put the packaged NaOH in a humidity controlled environment -- in other words, the desiccant goes outside the NaOH container, not with the NaOH. Here's one homemade storage solution....

"... No, I don't mean silica gel—I don't recommend using silica gel unless you understand its shortcomings..."

Please do not make a vague comment like this, because statements like these are not helping people to learn. If you want to educate and inform, then follow through. If you have information about using silica gel correctly, then please provide that info.

 

[paragon]

@Dawni Thank you, those links were helpful! I will assume every post/recipe except those by DeeAnna includes extra implicit superfat.

@DeeAnna I can't tell you how helpful that was! To respond:

• I removed the comment about silica gel. I won't further muddy the internet with another incomplete explanation, and incomplete is the best I could do.
• My lye is in its original container, so I inadvertently reinvented the "dry bucket" idea. For me it's a box, and I also use it for cyanoacrylate and some food products that like to clump.
  
• I loved the video about titrating lye--I've been looking for that info for a month. You forgot to mention baking the citric acid near 100°C to dehydrate it. Also, pouring your powders faster during titration will probably lead to a more accurate result because of the way cheap scales are engineered with "floating zero" or "zero tracking", a constant recalibration when small changes are detected. This may make a difference for the 0.1 g increments in particular.
  
• Kevin Dunn published a step by step titration in a PDF, and the procedure for detecting carbonates in lye: http://cavemanchemistry.com/HscgAlkali2015.pdf
  Though from a quick read, I can't tell whether this is any different than the steps you posted. I'll need to read both carefully before the next time I make soap.