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Saponification Value (SAP)
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With some recent discussion about Saponification and Saponification Values (SAP) I thought it might useful for those that may not know what they are and how they affect our glycerin byproduct and the saponification of the glycerin byproduct.

Saponification or SAP values are values of what percentage of lye it takes to convert one unit (gram, ounce, pound, etc.) of oil, fat or fatty acid into soap. To use the saponification values, multiply the SAP number by the number of ounces or grams of fatty acids, oils or fats. The result will be the same number of units of lye needed to fully saponify the product. Typically the sodium hydroxide (NaOH ) number is used to make bar soap and the potassium hydroxide (KOH ) number is used to make liquid soap. However we can push our glycerin byproduct in opposite directions.

For all intent and purpose the glycerin byproduct is already a soap. In traditional terms it would be a soap that is superfatted with saponifiable elements. But the superfat percentage is too high and this soap needs to be rebatched. And that is what we are doing we are rebatching the soap to use up the saponifiable elements that are left in the glycerin byproduct “soap”.

Why is a SAP value important?

A SAP value is important because it helps us to ensure that our final soap is not caustic hot and not overly superfatted. And in the case of our glycerin byproduct the superfatting agents can be any of the leftovers in the glycerin including biodiesel. Not exactly the superfatting agent of choice. A reliable SAP value for soap that will need a curing period, Cold Processed Soap, is important because after the 2-5 week curing time it can be disheartening to have to rebatch or toss the soap because it is caustic hot.

The leftovers in the glycerin byproduct each have a SAP value of their own. The leftovers are a soup of glycerides fatty acids and biodiesel. And of course soaps.

A SAP value for our glycerin byproduct will not very by adding any additional ingredients but the new ingredients will have a SAP value of their own. You simply use the SAP value for each of the ingredients being used in making your soap and work out how much lye is needed to saponify each. You then add these values together to get an amount of lye needed for all the ingredients in the soap recipe.

Whether we add extra ingredients and the lye necessary to saponify them or we strictly add only the amount of lye needed to saponify the saponifiable elements left in the glycerin the behavior of the glycerin byproduct remains constant -- the saponifiable elements left in the glycerin byproduct will be saponified resulting in more soap.

Here is an example of how this might apply.

I have 33oz of glycerin byproduct that I have determined that the glycerin byproduct has 22% saponifiable elements left. I want to add hardness to the soap because the glycerin byproduct is from soft oil reacted biodiesel and I have judged the Iodine value to be quit high or soft. I also like my soaps to lather well and hold that lather. And just for good measure I want to add some conditioning properties to my soap. I will add some shea butter as a superfatting agent because on its own unsaponified it has many beneficial properties.

To do this I will need 1.03oz of NaOH to fully saponify the glycerin byproduct. I will select steric acid for hardness, myristic acid for lather and hardness and oleic acid for conditioning. When using the traditional ingredients I will have to have enough lye to saponify those items. I will need 1.55oz lye to fully saponify these items. I will add 5% shea butter. I could have selected whole oils if I had wanted to but they would not participate in glycerin negation (a topic for another time).

This will be the resulting recipe;

33oz Glycerin Byproduct
4oz Steric Acid
4oz Myristic Acid
2oz Oleic Acid
1.03oz lye (for glycerin)
1.55oz lye (for the fatty acids)
.5oz Shea Butter
20oz Water


-Rick

http://www.knicenclean.com your single-most largest free BDG soaping content on the internet.
SAP Testing, Ingredient Properties, Soap Glossary and Recipes just to name a few.

Making Biodiesel Byproduct Soap Learn how to use your biodiesel byproducts to make great bar and liquid soap!!!

"Closing the loop on biodiesel production one bar at a time!"

Beware of the Dunning–Kruger effect.
 
Location: S.E. Michigan | Registered: April 15, 2007Reply With QuoteReport This Post
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Rick K., Great post and it gives a good explaination. I've been reading alot of threads on this subject of soap making and maybe I missed it but please explain the testing to determine the sap value? and are pool type test strips good for ph testing? etc.

I did make a small batch of soap (in a 12x12 tuperware) and although ok, after 3 weeks it's still alittle "spongey" I have used it and seems ok.
 
Location: kingman,az | Registered: May 25, 2008Reply With QuoteReport This Post
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Rick

Can you point us in the right direction on how to determin the SAP and Iodine values, thanks.

LW
 
Location: Midlands, UK | Registered: August 28, 2008Reply With QuoteReport This Post
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How did you calculate the amount of fatty acids in glycerine?
nikkij101
mercedes TD
 
Location: Portland, OR | Registered: November 08, 2008Reply With QuoteReport This Post
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i had made alot of batch useing glycerin by product.i tried so many recipe.it's true you could make hard soap from it.
but i'm wondering are you never test the pH of the soap(good soap had 9-10 pH range)
i use 30 gram NaoH 200 ML water 1 Liter GC.when i test the pH it's reach 13pH
it could not be use as bath soap.
 
Registered: April 02, 2009Reply With QuoteReport This Post
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Registered: April 02, 2009Reply With QuoteReport This Post



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It is very important to check the pH of your soap. This is done once the soap has cured if using the cold process (CP) method or at the end of hot processing (HP). The pH of the soap should fall between 8 and 9.5. A quick and simple test is the "battery test". This is done by touching the soap with your tongue. If you get a bite similar to the bite of a 9volt battery the soap is caustic hot and should be adjusted. I use pH strips or a pH meter when testing my soap.

I always calculate a SAP value for every batch of glycerin I use. I have found that for me one size does not fit all. I have several sources of glycerin byproduct. My own glycerin is usually about 30% saponifiable elements where as some I get from another source is 12% saponifiable elements. Yet another is 25%.

In addition I always hot process my soap. This is good for several reasons. One and most important is it allows you to check and adjust the pH of the soap without having to re-batch after the cure time. Another is that the soap is useable as soon as you finish the batch. Another plus to hot processing is that you can add your super fatting agent at the end of the process and be able to ensure that you are not super fatted with the saponifiable elements (mostly biodiesel). Other things such as adding transparency is only possible if you hot process your soap.

Bar soap is quite possible from our biodiesel glycerin byproduct even the KOH reacted glycerin byproduct. In fact by adding only a few extra ingredients you can add hardness to the soap and other desirable properties.

Liquid soap is venerable to becoming rancid and it is very important to ensure that the soap is fully saponified. Liquid soap can be made purposely a little caustic hot, pH10 - pH11 and then backed off with some citric acid, boric acid, or borax. An added benefit to using borax is that it can also add viscosity to the liquid soap. This is important as the liquid soap is diluted up to or even more than 50%. The soap can be quite thin by that time. Another option for viscosity is to keep it concentrated and less dilute.


-Rick

http://www.knicenclean.com your single-most largest free BDG soaping content on the internet.
SAP Testing, Ingredient Properties, Soap Glossary and Recipes just to name a few.

Making Biodiesel Byproduct Soap Learn how to use your biodiesel byproducts to make great bar and liquid soap!!!

"Closing the loop on biodiesel production one bar at a time!"

Beware of the Dunning–Kruger effect.
 
Location: S.E. Michigan | Registered: April 15, 2007Reply With QuoteReport This Post
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i'm glad rick k was here to share with us
rick can you share your recipe here or contact me by e-mail,i would like to study your recipe.
from your comment here i guess you where expert in soap making.
calculate SAP value is the correct way to make a soap.
 
Registered: April 02, 2009Reply With QuoteReport This Post
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Soap Maker,

I would be happy to share with you. Here is a good recipe that assumes 25% saponifiable elements in your biodiesel glycerin byproduct. Of course you will pH test the final soap to see if you need more or less than 25%.

You could substitute myristic acid and steric acid for the coconut oil and oleic acid for the olive oil. This would allow for some glycerin negation. If you substitute you will need to recalculate the amount of NaOH for the pure fatty acids.

=====================================================

80oz NaOH glycerin byproduct
20oz Coconut Oil
5oz Olive Oil

2.8 oz NaOH for the Glycerin Byproduct
4.45 oz NaOH for the whole oils

52oz water. (More can be used when hot processing)


-Rick

http://www.knicenclean.com your single-most largest free BDG soaping content on the internet.
SAP Testing, Ingredient Properties, Soap Glossary and Recipes just to name a few.

Making Biodiesel Byproduct Soap Learn how to use your biodiesel byproducts to make great bar and liquid soap!!!

"Closing the loop on biodiesel production one bar at a time!"

Beware of the Dunning–Kruger effect.
 
Location: S.E. Michigan | Registered: April 15, 2007Reply With QuoteReport This Post
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I've made several batches using Rick's help and I finally think I've got it. Hot processing for me is definately the way to go. Before I was having to wait for weeks just to find out that the soap I had tried to make was way caustic. Now I put in about 20-25% saponifiables, usually coconut or castor oil and add enough lye water to saponify that and I am making some really nice soap now. I have a PH tester so I just monitor the ph while I am heating it. When it gets to an acceptable level (below 9.75 for me) I am done. The oils you add make a big difference in whether you get lather or not. I just couldn't get acceptable lather with my glycerol (peanut and canola derived).

I still use my raw gycerol for a degreaser and cubie-cleaner but I use my good stuff on the family.

Thanks Rick!
 
Location: Asheville, NC | Registered: January 19, 2009Reply With QuoteReport This Post
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By the way, I am making liquid soap because I use KOH to make my diesel. My oils, peanut and canola, aren't the best for hard soaps either. They make great liquid soap though!
 
Location: Asheville, NC | Registered: January 19, 2009Reply With QuoteReport This Post
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dear ricky
i wanna ask you.how much citric acid/gram did you gave to make pH drop to level 9.5
 
Registered: April 02, 2009Reply With QuoteReport This Post



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