Confused about chemistry

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GirlinScience

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Hello all, I am a high school science teacher living in Morocco and I want to start making my own soap. Here we have lots of different ingredients on hand cheaper than most and the commercial products tend to be really pricey by comparison, so that and the fact that most soap irritates my skin makes me think making my own would be better. I was researching the chemical reaction and don't know where to get reliable SAP values for using NaOH, also I kept finding recipes mentioning different concentrations of NaOH used (between 9 and 10.5 M?) is there a molarity usually used? Also how will I know the final pH of my soap? I understand it is hard to know exactly what percent of oils in your mix will be saponified but I don't like the guess work and most places' math does not add up. I don't want a dangerous product.
 

Mobjack Bay

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Welcome to the forum.

Perhaps it has been difficult for you to find the right information using a search engine from Morocco, but, actually, there are many good resources for beginners online, including this forum.

A soap calculator will do all the calculations for you and allow you to formulate a safe recipe. Check out SoapCalc.com or SoapMakingFriend.com or Soapee.com. Here’s a link to a tutorial for SoapCalc in the SMF beginners forum. Measuring the pH of soap is not necessary if your recipe is formulated properly. The beginners forum has recipes you can use as a starting point and you can post there any questions you have or to get feedback on a recipe.

here are some other links with useful information:
http://www.soaping101.com/
https://www.modernsoapmaking.com/category/soap-recipes-and-tutorials/
 

DeeAnna

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Soap making isn't typically done using molarity/molality. We aren't doing quantitative analysis. ;) If you want to talk in terms of molar concentration, you'll get a lot of blank looks from soap makers.

We normally work in percentage by weight; that's sufficiently accurate for our purposes. The NaOH concentration used for soap making ranges anywhere from 25% to 50% w/w (meaning 25 g NaOH in 100 g finished solution, and so on) with a typical range being 28% to 33%.

The usual recommendation is to use an online soap making calculator, unless you feel a great need to do calculations by hand. My suggestion is to check out https://www.soapmakingfriend.com/soap-making-recipe-builder-lye-calculator/

Of course the calculations can be done by hand -- online calculators didn't exist 20 years ago -- but I don't think a lot of people do that nowadays given there are online calcs that are accurate and reliable. If you want to learn about the required calculations, however, here's a good article from a reputable soap maker about the process -- https://auntieclaras.com/2018/09/lye-calculation-tutorial/ If you have questions, I'll be happy to help.

There are several reasons why you see some variation in the answers from any soap calculation. One of the main reasons is that saponification values used for these calculations are averages. And the databases for the various calcs aren't all exactly the same because various sources for sap values report slightly different averages.

Unless you test YOUR fats for their sap value, the numbers you calculate won't be perfectly accurate either. The variability in sap values and alkali purity is an important reason for why most soap calculations include some superfat -- meaning a small amount of excess fat.

We provide an excess of fat as a safety factor to account for small errors in measuring out the ingredients and to allow for some inaccuracy in the numbers our recipes are based on. Based on my experience (chemical engineer and former chem lab tech), the margin required to ensure safety is 1-2% superfat. Anything higher than that is personal choice.

The chemistry you're dealing with is not a simple acid-base neutralization where the reaction endpoint is a black-and-white answer. The pH of finished soap with no excess alkali will range from about 9 to about 11.5 depending on the fatty acids in the soap. A soap that has a pH of 10 might have excess alkalinity (not good) or it might have excess fat (desirable) -- the pH test alone simply cannot give you a definitive answer. There are other issues as well, but this is the key issue in my opinion about why pH alone isn't a particularly helpful test.

A titration for excess alkalinity is the correct test, so if you're wanting numbers to rely on, you will need the correct equipment, reagents, and procedure to do this titration. An alternative to an excess alkalinity test is what we call the "zap" test. You can find a tutorial about the zap test in the Lye Based Soap forum here.

I won't get into detail about the other issues you raise about not wanting to make a dangerous product. Suffice to say most of us, including me, can reliably and repeatedly make safe soap without ever testing excess alkalkinity, saponification values, purity analyses of the alkalis, etc. If you want to take the tack of measuring the numbers, by all means it can be done. But it's not strictly necessary to ensure product safety.
 
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GirlinScience

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Welcome to the forum.

Perhaps it has been difficult for you to find the right information using a search engine from Morocco, but, actually, there are many good resources for beginners online, including this forum.

A soap calculator will do all the calculations for you and allow you to formulate a safe recipe. Check out SoapCalc.com or SoapMakingFriend.com or Soapee.com. Here’s a link to a tutorial for SoapCalc in the SMF beginners forum. Measuring the pH of soap is not necessary if your recipe is formulated properly. The beginners forum has recipes you can use as a starting point and you can post there any questions you have or to get feedback on a recipe.

here are some other links with useful information:
http://www.soaping101.com/
https://www.modernsoapmaking.com/category/soap-recipes-and-tutorials/
Thanks for the links, I didn't know which calculator to trust.

Soap making isn't typically done using molarity/molality. We aren't doing quantitative analysis. ;) If you want to talk in terms of molar concentration, you'll get a lot of blank looks from soap makers.

We normally work in percentage by weight; that's sufficiently accurate for our purposes. The NaOH concentration used for soap making ranges anywhere from 25% to 50% w/w (meaning 25 g NaOH in 100 g finished solution, and so on) with a typical range being 28% to 33%.

The usual recommendation is to use an online soap making calculator, unless you feel a great need to do calculations by hand. My suggestion is to check out https://www.soapmakingfriend.com/soap-making-recipe-builder-lye-calculator/

Of course the calculations can be done by hand -- online calculators didn't exist 20 years ago -- but I don't think a lot of people do that nowadays given there are online calcs that are accurate and reliable. If you want to learn about the required calculations, however, here's a good article from a reputable soap maker about the process -- https://auntieclaras.com/2018/09/lye-calculation-tutorial/ If you have questions, I'll be happy to help.

There are several reasons why you see some variation in the answers from any soap calculation. One of the main reasons is that saponification values used for these calculations are averages. And the databases for the various calcs aren't all exactly the same because various sources for sap values report slightly different averages.

Unless you test YOUR fats for their sap value, the numbers you calculate won't be perfectly accurate either. The variability in sap values and alkali purity is an important reason for why most soap calculations include some superfat -- meaning a small amount of excess fat.

We provide an excess of fat as a safety factor to account for small errors in measuring out the ingredients and to allow for some inaccuracy in the numbers our recipes are based on. Based on my experience (chemical engineer and former chem lab tech), the margin required to ensure safety is 1-2% superfat. Anything higher than that is personal choice.

The chemistry you're dealing with is not a simple acid-base neutralization where the reaction endpoint is a black-and-white answer. The pH of finished soap with no excess alkali will range from about 9 to about 11.5 depending on the fatty acids in the soap. A soap that has a pH of 10 might have excess alkalinity (not good) or it might have excess fat (desirable) -- the pH test alone simply cannot give you a definitive answer. There are other issues as well, but this is the key issue in my opinion about why pH alone isn't a particularly helpful test.

A titration for excess alkalinity is the correct test, so if you're wanting numbers to rely on, you will need the correct equipment, reagents, and procedure to do this titration. An alternative to an excess alkalinity test is what we call the "zap" test. You can find a tutorial about the zap test in the Lye Based Soap forum here.

I won't get into detail about the other issues you raise about not wanting to make a dangerous product. Suffice to say most of us, including me, can reliably and repeatedly make safe soap without ever testing excess alkalkinity, saponification values, purity analyses of the alkalis, etc. If you want to take the tack of measuring the numbers, by all means it can be done. But it's not strictly necessary to ensure product safety.

I understand your points, the issue for me is while I have found lots of information online and the reaction is straight forward I didn't feel like there was enough information in terms of what can affect the behaviour of the soap in the end. Using excess fat is obvious but different places had different SAP values and recipes don't explain well or don't mention water volume which is why I wanted to know the concentration of acid. the final pH of the soap is important to me because I would prefer to end up with a pH neutral soap. I was trying to research which specific salts (the soap I mean) are made from certain oils like olive oil or sunflower oil but they aren't mentioned. I like to know as much as possible before trying something.
 
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shunt2011

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I understand your points, the issue for me is while I have found lots of information online and the reaction is straight forward I didn't feel like there was enough information in terms of what can affect the behaviour of the soap in the end. Using excess fat is obvious but different places had different SAP values and recipes don't explain well or don't mention water volume which is why I wanted to know the concentration of acid. the final pH of the soap is important to me because I would prefer to end up with a pH neutral soap. I was trying to research which specific salts (the soap I mean) are made from certain oils like olive oil or sunflower oil but they aren't mentioned. I like to know as much as possible before trying something.
You will never have a neutral PH in handmade soap. Soap will have a PH of 8.5-11 some even higher. Neutral wouldn't be soap. Also, doing a zap test is the best way to know if their is any excess lye. PH testing does nothing really as it will always have a high PH.
 

DeeAnna

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"...the concentration of acid...."

Do you mean concentration of alkali?

"...recipes don't explain well or don't mention water volume..."

Well, no, they don't provide water volume. All modern soap recipes are based on weight not volume. Some very old recipes do use volume, but those are the exception, not the rule.

Soap recipes HAVE to provide total water weight and total dry alkali weight. If they didn't, you couldn't make the soap. Given your science background, you can calculate the lye solution concentration from those two numbers, easy peasy.

All of the recipes calculated by every soap recipe calculator I've looked at also provide the lye concentration as well. Have you looked at the results from the Soapmaking Friend calc or Soapcalc or Soapee? Take a closer look at recipes calculated by any of these calculators and you'll find the information you're looking for.

"...a pH neutral soap..."

That's not going to happen. Soap that has a neutral pH (pH = 7) is no longer soap -- at that pH, the soap will decompose into fatty acids.

If you mean chemically neutral, as in no excess alkali and no excess fat, then the pH will be as I mentioned earlier -- anywhere between 9 and 11.5 depending on the fatty acid profile of that particular soap. Soap is an alkaline salt of a weak acid and strong base. It is not a neutral salt of a strong acid and strong base.

"...I was trying to research which specific salts (the soap I mean) are made from certain oils like olive oil or sunflower oil but they aren't mentioned...."

Sodium olivate is the generic name for olive oil soap. But the specific fatty acids in olive oil are what I think you're after.

Any reputable soap recipe calculator can provide a typical fatty acid profile for any given fat. Enter a weight in the calc for the fat you're interested in and have it calculate a recipe using that single fat. The resulting fatty acid profile given in the recipe will be for that fat.

Olive oil contains roughly 70% oleic acid with some linoleic and palmitic acids (roughly 13% each), and a dab of linolenic and stearic acids (1-2% each). The salts that make up an olive oil soap are the sodium salts of each of these fatty acids if you use NaOH to saponify the fat.
 
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Becky1024

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Soap is the product of an acid base reaction (the fatty acids on the oils / butters and the base from the lye). If you react an acid and a base together, you get a salt plus water. In the case of soap you get the sodium salt of your fatty acids. The reaction is at equilibrium, meaning that if you change parameters like temperature, concentration, or pH you can make the reaction product favored (more products, less reactants) or reactant favored (less product, more reactant). The effect of pH is that a basic pH (higher than 7) will favor the product side, meaning more sodium salt of your fatty acids. If the pH is neutral or acidic (equal to or less than 7) it favors the reactants, meaning more oil / butter. So soap must stay on the basic side to remain soap!
 

Todd Ziegler

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Welcome to the forum. I think you will find that the responses that you have gotten, are going to be the best information you receive from any place or persons.

I have learned to heed the advice that these people have given in this post. I was making things more difficult for myself then it should have been. I gathered a lot of information before I tried my first CP batch and it did help. However I quickly realized that the experience of actually making soap, gave me the chance to ask better questions and to better understand the information that I had read from this forum.

I really think the best advice that I received in the beginning was to keep it simple and small for the first batch. Don't over think it or make it more complicated than it needs to be. Listen to what they are saying because they know what they are doing. Your best ingredient will be, keeping it simple. The other thing is, what you think of as a failure, is really a success, because you gain unimaginable knowledge from just doing it.

Be creative and think out of the box all that you want but remember it's not rocket science lol.
 

DeeAnna

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...a basic pH (higher than 7) will favor the product side, meaning more sodium salt of your fatty acids. If the pH is neutral or acidic (equal to or less than 7) it favors the reactants, meaning more oil / butter. So soap must stay on the basic side to remain soap!
Actually the pH needs to be quite a bit more alkaline -- in that 9 to 11.5 range I keep mentioning -- in order for the saponification reaction to go to completion. The reaction will definitely not be complete if you stop it when the pH is 7. Or even a pH of 8.

Saponification is a particular kind of acid-base reaction -- it is the reaction of a strong base (sodium hydroxide) with a weak acid (fatty acids). The weak acid does not fully dissociate and the strong base does. The difference in how weak acids and strong bases behave is the reason why the soap solutions have an alkaline pH, not neutral (ph 7) or acidic (pH below 7). I got into this subject a little bit recently -- https://www.soapmakingforum.com/threads/oh-no-the-zaps.78711/#post-820204

If you add acid to a soap solution, you do indeed shift the reaction toward the reactant's side of the chemical equation, but most people usually expect a steep, linear drop in pH. That doesn't happen. Instead you will create a buffer solution. A buffer is a type of chemical mixture that has a relatively stable pH as OH- or H+ ions are added. A soap and fatty acid buffer acts to maintain an alkaline pH as H+ ions are added.

If you add enough acid, however, you will eventually overwhelm the buffer system. When it breaks down, the pH will begin to change more rapidly. By the time you add enough acid to the soap and fatty acid mixture to get the pH down to 7, the mixture will be mostly fatty acids, however, not soap. (The reactant in this situation is not fat by the way; it's fatty acids.) A fatty acid mixture might foam up some, but it will be greasy feeling and definitely will not function as a cleanser.
 

DeeAnna

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I realize the last few posts I've made were going to result in people having glazed eyeballs. Since some of the participants in this thread have mentioned they have science backgrounds and sound like they know the science-y lingo, I'm giving my inner geek a little looser rein than usual. But I promise I'll tone it down from here on. :D
 

gloopygloop

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I realize the last few posts I've made were going to result in people having glazed eyeballs. Since some of the participants in this thread have mentioned they have science backgrounds and sound like they know the science-y lingo, I'm giving my inner geek a little looser rein than usual. But I promise I'll tone it down from here on. :D
Highly informative and interesting, dont tone down too much we need to learn and understand somewhat things which are not our subject, if even a little bit goes in its really worthwhile, thank you.
 

dibbles

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I realize the last few posts I've made were going to result in people having glazed eyeballs. Since some of the participants in this thread have mentioned they have science backgrounds and sound like they know the science-y lingo, I'm giving my inner geek a little looser rein than usual. But I promise I'll tone it down from here on. :D
Don't tone it down. If someone doesn't want to read through it, they can skip over it. I think having the information out there for those who find it interesting is a good thing. And I am also one that is not a scientist and don't always understand it, but I think it's good to have it out there.
 

Becky1024

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I realize the last few posts I've made were going to result in people having glazed eyeballs. Since some of the participants in this thread have mentioned they have science backgrounds and sound like they know the science-y lingo, I'm giving my inner geek a little looser rein than usual. But I promise I'll tone it down from here on. :D
DeeAnna, as a fellow chemistry geek I enjoy your lingo! I teach a couple of chemistry courses at a local college. We just finished saponification of lipids in one, and are about to hit acid / base reactions in another. Fun!
 

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Thanks for the encouragement, everyone. I appreciate this ... a lot!
I didn't completely understand some of the old posts that you made but I understand that what you had to say was important and it was my responsibility to learn & understand what you had said. That is how I and anyone else becomes a good soap maker.

Now I can read anything you post and understand it. If I have a problem understanding something that you wrote, then I do some research or ask questions. I'm not a chemist/scientist by a degree, however I love science and taught myself a lot, so it was easier for me to understand what you wrote.

"Understanding & learning will only be achieved with hands-on experience. " my grandma

She also like to say "I can teach you all day long, but until you get on the tractor, you won't learn a d**n thing, so shut up and start it." she was a colorful lady and definitely the leader of our family.
 

DeeAnna

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I haven't taken anything anyone has said as a knock against me. S'okay! Really it is.

I have wanted to explain more about the buffering ability of soap and fatty acids for some years now and also to explain why soap must have an alkaline pH if you want it to be a functional, useful soap. They're inter-related subjects and not easy (even for me) to understand.

Some of you long-time members might know this recurring issue of pH testing for soap is a "hot" topic for me. I have known what I want to say, but I've had trouble deciding how to explain the science in (more or less) everyday words.

Again, I'm appreciative and thankful for your encouragement.
 
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