What does SF mean in a recipe?

[McSpin]

That analogy is not hard to follow, but it doesn't explain the chemistry that I was hoping to find. I've always been a person who like to know why. That does not explain why or how it happens - just that it does.

How did someone initially determine this? I can understand that the lye doesn't use all of the stearic acid before it acts upon another fatty acid, but if the rate of reaction differs, then it should convert the stearic acid faster, leaving a different ratio at the end of saponification compared to the start. I'm curious what that ratio is and how it is determined. By the sounds of it, someone has figured this out, but I'm not finding the detail anywhere.

 

[Susie]

OK, then you probably need to go to the source for info:

http://www.amazon.com/dp/1935652095/?tag=skimlinks_replacement-20

If it is not the right book, it will be in one of his books. Or you can go get a membership in fyi101.com:

http://fyi101.com/superfatting-and-lye-discounting-part-i-presented-by-dr-kevin-dunn/

 

[McSpin]

The book looks like it would be a good one to have even if it doesn't give the answers I'm looking for.

 

[topofmurrayhill]

In cp, it will be pretty much a split of all your oils based on their ratios. So if you make a cp soap with 50% lard, 30% oo and 20% co, your 5% superfat will be made up of a similar ratio of those oils.

I must respectfully disagree. The lye does not see oils; it sees fatty acids. It will preferentially react with free fatty acids and more saturated fatty acids. Whatever oil remains in the soap is unlikely to resemble any oil that was in your recipe.

Thus even if you make a one-oil soap with a generous lye discount, I don't believe it is valid to say that the soap is superfatted with that oil.

One might say that in cold-process soapmaking, the original oils used in the formulation, whether one or many, are essentially destroyed.

 

[not_ally]

Damn it, why do guys always prefer blondes! In soap as in life, apparently EG, if you make another analogy about all the tall girls being taken up first, I may have to use a frowny face emoticon!

 

[The Efficacious Gentleman]

I must respectfully disagree. The lye does not see oils; it sees fatty acids. It will preferentially react with free fatty acids and more saturated fatty acids. Whatever oil remains in the soap is unlikely to resemble any oil that was in your recipe.



Thus even if you make a one-oil soap with a generous lye discount, I don't believe it is valid to say that the soap is superfatted with that oil.



One might say that in cold-process soapmaking, the original oils used in the formulation, whether one or many, are essentially destroyed.

The fatty acids that we use for soaping are commonly referred to as oils. They are fatty acids, of course, in many cases they are also triglycerides, but they are very often oils. To use that term is not correct, in sure you'd agree. Unless you think that a fatty acid used in soaping is NEVER also known as an oil?

I also disagree with your disagreement. It would be wrong to say that, if I make a single oil soap (let's say a Castile) and have a 0% lye discount that my soap has olive oil - it doesn't, it has sodium or potassium olivate.

If I had a 5% lye discount, that means that 5% of the olive oil did not react with lye - the triglyceride is still intact, the olive oil has not changed in any way - it is still olive oil. Lye creates soap by breaking the fatty acid down and joining with the parts that are left. So there is not enough lye in a lye discounted soap to do that, so there must be oil left as oil (or fatty acids left as fatty acids, if you really must)

 

[topofmurrayhill]

If I had a 5% lye discount, that means that 5% of the olive oil did not react with lye - the triglyceride is still intact, the olive oil has not changed in any way - it is still olive oil. Lye creates soap by breaking the fatty acid down and joining with the parts that are left. So there is not enough lye in a lye discounted soap to do that, so there must be oil left as oil (or fatty acids left as fatty acids, if you really must)

Your olive oil is a collection of fatty acids in the form of triglycerides. Those fatty acids are present in proportions that are characteristic of olive oil. Introduce lye and the fatty acids react with the caustic at different rates. Once the process is complete, virtually all of the saturated fatty acids (palmitic, stearic) will have become soap. We began with a large amount of monounsaturated oleic acid, and certainly some of that will be left over. We began with a modest amount of linoleic acid, but it saponifies very slowly, so I imagine some of that will be left over too, if not most of it.

As you see, the caustic has cherry-picked it's favorite fatty acids and turned them into soap, and left behind the ones it doesn't like as much. The proportions remaining as oil have changed, and many of the triglycerides have been broken up. If you could extract all the material left over from the original olive oil, it would not resemble olive oil in composition or properties at all.

 

[The Efficacious Gentleman]

That is interesting - can you link to the study with the numbers on that? I also think McSpin would enjoy that

ETA - I ask, because it would be interesting to see how the whole probability question is answered: a certain fatty acid saponifies more easily, but does that always mean that, if 1 molecule is more easily saponified is also 'competing' with 4 others that are slower, does the first ALWAYS go first, or does probability come in to play?

 

[topofmurrayhill]

That is interesting - can you link to the study with the numbers on that? I also think McSpin would enjoy that

ETA - I ask, because it would be interesting to see how the whole probability question is answered: a certain fatty acid saponifies more easily, but does that always mean that, if 1 molecule is more easily saponified is also 'competing' with 4 others that are slower, does the first ALWAYS go first, or does probability come in to play?

I'm sure that you're correct in thinking of it in terms of probabilities. They wouldn't saponify in order. They would saponify simultaneously, but at different rates until the caustic runs out. Those rates vary significantly though. You see how much faster the reaction goes with coconut oil (lauric, myristic) or palm oil (palmitic) or butters (stearic) or heaven forbid free stearic acid. Blammo. I would think those saturated fatty acids would get more or less completely gobbled up in most cases.

Think about how much more laid back it is making castile soap. Should be plenty of opportunity for the palmitic (and some stearic) in the olive oil to react while the lye is chewing on the oleic.

I don't know of numbers regarding the dynamics of this. I'm speaking in terms of basic principles and simpler experiments, which I believe are on your bookshelf. I don't have it handy, but I was the primary proofreader for Scientific Soapmaking. I've gone through it page by page, sentence by sentence, checked every calculation, did every problem. Relevant parts would include the chapter on superfatting, the stuff about single-oil soaps, and more.

 

[The Efficacious Gentleman]

Interesting idea, but does the rate of saponification have such a bearing on the finished result? So if we are talking about how long it takes from the start of the process to the end of the process, that has little impact if there is no real difference in how quickly the raw lye molecules start to bind with the fatty acids.

To use the analogy of the party, while it make take a long time to talk a brunette in to letting you walk her home and steal a kiss on the cheek on the door step compared to how long it takes to talk the blonde in to the same thing, if within 5 minutes of the party starting people are already paired up and the chaps are sweet talking the ladies, the mix of the girls left alone won't be dependent on how long the sweet talking takes as once it is started, that particular couple are paired up.

It's not like a chap starts talking to a brunette, get's bored and finds a blonde - once the lye has started to bind with an acid, it won't then stop and find another acid that is easier, will it?

Edited to add, unless the rate also indicates how easy it is for the process to actually start in the first place

 

[topofmurrayhill]

It's not like a chap starts talking to a brunette, get's bored and finds a blonde - once the lye has started to bind with an acid, it won't then stop and find another acid that is easier, will it?

Well I reckon that is a very good question. I remember reading -- I think in some industry material I turned up -- that exactly such a thing happens as an ongoing process after the soap is produced. So the residual oil in the soap could continue to change due to the wanderings of promiscuous sodium ions. I'll let you know if I can figure out where that was.

However, I don't think that process is necessary to transform the residual oil in our soap. Even if the saponification proceeds quickly, unsaturated fatty acids are big contributors to that speed. At the other end of the spectrum, polyunsaturated fatty acids are feeling like relative wallflowers. Read about the linoleic single-oil soap in Dunn's book and how recalcitrant it was about being soap.

One interesting issue you've brought up with the matter of bored wandering lye is to what extent even the superfat oil in HP soap could change over time. I couldn't say for sure, but as crafters there is still much we might learn.

Edited to add, unless the rate also indicates how easy it is for the process to actually start in the first place

Yes, I think something like this might be the way to think about it. Or maybe whether the guys are preferentially attracted to certain girls. In deference to not_ally, I would suggest the brunettes are more in demand.

 

[Susie]

Having just spent an hour on another forum, I have to tell y'all how wonderful it is to read people disagreeing, but having a good discussion that helps everyone learn more about soapmaking, and it not degenerate into ad hominem attacks and name calling!

 

[The Efficacious Gentleman]

I think it is because most people here are willing and eager to learn.

 

[McSpin]

TEF posted this link in another thread:
http://cavemanchemistry.com/LyeDiscount-Dunn.pdf

It seems to verify that the fatty acid profile of the superfat is not the same as the initial oils used - at least for the 3-4 combos that were tested in this article. It seems to support topofmurrayhill's theory.

 

[The Efficacious Gentleman]

TEF posted this link in another thread:
http://cavemanchemistry.com/LyeDiscount-Dunn.pdf

It seems to verify that the fatty acid profile of the superfat is not the same as the initial oils used - at least for the 3-4 combos that were tested in this article. It seems to support topofmurrayhill's theory.

There is also another thread discussing a similar topic, the idea that fatty acids (non triglycerides) can "easily" swap around, but it raised the question of whether or not triglycerides can be affected in the same way due to the strength of the reaction required, plus how much time is required. Might be interesting read for you.

 

[McSpin]

I saw that, but like you mentioned in that thread, time was a factor they didn't discuss and it really is important to know that in order to understand the meaning a bit better.

 

[tbeck3579]

What Party? Where? Who?

This is such an intelligent group of people assembled here! Very refreshing!

I joined this wonderful forum today in search of the "perfect" soap recipe -- perfect for my skin type and personal hygiene preferences. I've been dabbling in soap making for many years; always CP, but HP is looking a bit more appealing. After reading this thread I'm thinking CP soap may not be the ideal soap for me. Thank you so much for this debate! It helped me to think through the science of soap making and helped me with my quest. You folks are the best!

As I was reading this thread I couldn't help but think there must be MANY variables in making soap. Just a quick search and that hunch seems to be correct. This study, for example: -- Variations in the temperature and in the composition of the medium alter the proportions of individual fatty acids. So not only being blond, but possible ethnicity (German or Norwegian) in a room that is warm from too many party goers can influence the outcome. There is so much to consider when "cooking" that perfect bar of soap

 

[McSpin]

This study, for example: -- Variations in the temperature and in the composition of the medium alter the proportions of individual fatty acids.

Let me see if I understand what you quoted. Is the study saying that the fatty acids saponify in a different ratio at different temperatures?

 

[tbeck3579]

McSpin,

The study states that temperature changes proportions of fatty acids, as does the medium - following that through to a logical conclusion means it will change saponification because saponification relies on the availability of fatty acids. I should say my view of this is, environmental conditions (medium and temp) will change the outcome because the fatty acids have changed. I was thinking in terms of the huge variations in the oils used in soap recipes, and even the slight differences in the temperatures when "cooking" it. However, even the genetics of different olive trees would have some impact -- in my mind anyway. Logical, but I hadn't given it that much thought before this discussion. A change in temp and/or medium will change most things, either minutely or drastically. It doesn't take an advanced science degree to validate the hypothesis, but he has one, and did. I love science because scientists are always trying to prove "it ain't so" Well, I should say I love science that isn't bought and paid for in an effort to sell something to someone. Mark Twain hit the nail on the head when he said, "lies, damn lies, and statistics."

Take care,
Teresa

 

[DeeAnna]

^^^^ Yes.