Testing for Superfat?

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newtosoap101

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Hi there! I've made a couple of batches of soap with moderate success. My primary reason for making soap right now is to use it in a homemade laundry powder recipe that includes borax, washing soda, and grated soap. I made one batch a couple of years ago and haven't had to make another because it lasted so long! I just about ran out and so I went to make another batch. I'm using this just for cleaning laundry and so want close to 0% superfat. I used mostly Crisco (hydrogenated soybean oil) and a bit of olive oil. I used a soap calculator on Bramble Berry and came up with this recipe for crockpot soap:

LYE & LIQUID AMOUNT
Lye (Sodium Hydroxide) -- 5.98 oz
Ounces of liquid -- 14.52 oz
Total 20.50 oz

OILS & FATS AMOUNT %
Olive Oil -- 3.00 oz 6.8 %
Shortening (Soybean) -- 41.00 oz 93.2 %
Total 44.00 oz 100 %

TOTALS AMOUNT
Lye & Liquid -- 20.50 oz
Oils & Fats -- 44.00 oz
TOTAL BATCH YIELD -- 64.50 oz

Here is my issue: I can't remember if I put 4.98 or 5.98 ounces of lye in. The batch is cooling in a milk carton now, but I'm worried I didn't put enough lye in and so the batch will have a very high superfat and so be bad for laundry use. I could rebatch the soap and add another ounce of lye, but then if I DID put in the right amount of lye the first time I would have a lye heavy soap. Is there a way I can tell the superfat of a soap? I tried washing my hands with the stuff left in the crockpot to see if it felt drying or moisturizing and I just can't tell! :confused:
 

newtosoap101

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Perhaps I am misunderstanding superfatting... I thought if there was a 0% superfat, then none of the fat would be left in the soap, which would mean none of the fat would get into the clothes, right? Why would it matter what kind of fat you use then?

This is similar to the recipe I used last time and it worked just fine for me. My concern this time is that there may be fat left in the soap (if I accidentally did not add enough lye).
 

cmzaha

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I use a -5% superfat in 100% coconut oil soap for laundry. Soap calculators take an average sap value for oils and also have a margin for error so even a 0 superfat is most likely not a 0. Granted it could go plus or minus superfat. Unless you know the exact sap of an oil it is impossible to be exact. Even at a -5% I have never had a batch zap and if it did time would fix it
 

IrishLass

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Hi Newtosoap!

Although several folks make laundry soap with 100% CO, I happen to know of lots of people that use 100% lard or tallow with a 0% superfat to make great laundry soap, so no worries there. :)

I have no guaranteed surefire advice to offer to tell if your soap is truly superfatted at 0% or not, but if you added only 4.98 oz lye, that means your soap is superfatted at about 17.5%, which is a very substantial superfat. How soft is the soap? I would think that it would be quite soft if it were superfatted that much.

Barring all else, if it were me, I would try washing a small sample load of dirty/oily rags with it to test it out.


IrishLass :)
 

cmzaha

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If like IL just mentioned if you soap ended up with a 17% superfat, believe me you will feel the oil. If it does not feel oily I would say you used the higher amount of lye. But I am one that does low superfat in almost all soap so I tend to feel the oil.

Lard does make decent laundry soap, but I like a 50/50 lard coconut oil mix. I like to make my laundry soap with a 100% coconut oil and 100% lard so I can mix them when I grind. I always keep some of the 100% coconut soap for really dirty grimy cloths and my outdoor tablecloths
 

newtosoap101

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Thanks for the helpful replies! Right now the soap is quite soft, but I just made it this afternoon so it is still cooling down. I'll cut a chunk off tomorrow and use it to wash some rags as suggested. I think I'd feel more oily after using it if it was 17.5% superfat so I probably added the correct amount of lye and am just being paranoid.

Interesting that you can make soap with a negative superfat! That would scare me because I'm terrified of lye right now (maybe it will get less scary as time goes by), but it's good to know it can be done!
 

The Efficacious Gentleman

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Perhaps I am misunderstanding superfatting... I thought if there was a 0% superfat, then none of the fat would be left in the soap, which would mean none of the fat would get into the clothes, right? Why would it matter what kind of fat you use then?

.....

This is because the lye and the oils combine to make a certain kind of soap, made up of salts of fatty acids mainly. So if you used only olive oil, your soap would be sodium olivate (when using sodium hydroxide!) but if you used coconut oil it would be sodium cocoate. If you used a mix of the two then your soap would be a mix of the two sodium xxxxates.

Many people find that a sodium cocoate soap is best for laundry use, especially as ungrated bars make excellent stain sticks.
 

DeeAnna

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And the different fatty acids make soap that behaves differently. It's like using milk chocolate and semisweet chocolate and bitter chocolate. If they were all the same, then it would not matter what kind of chocolate you would use -- you'd only need one kind, right? But they're not the same, and neither are the fatty acids in the fats we use to make soap.

Sodium cocoate (coconut oil soap) is different from sodium olivate (olive oil soap) is different from sodium palmate (palm oil soap) ... and etc. Cocoate soap is very soluble in water, lathers well with big fluffy bubbles, and can be drying and harsh to the skin. Palmate can make a soap that is fairly insoluble in water, lathers less freely to make a small creamy foam, and is fairly mild to the skin. And olivate and the others fall somewhere in between.

A zero superfat is theoretically the point where there is no extra lye and no extra fat left in the soap after saponification is completely done. Real life is messier than theory, so one needs to keep that in mind. We don't measure the actual saponification value of the fats we are actually using, so the calculations are based on averages. We don't measure the actual purity of the lye we use, so again the calculations are based on an estimate. Even the best scale makes tiny errors when measuring. And the chemical process of saponification comes with its own uncertainties.

This real life messiness means it's wise to build in at least a small positive superfat when making a soap for the skin. This ensures the soap will have a bit of extra fat rather than a bit of extra lye when saponification is done. Better to err on the safe side (too much fat).

Even though I advise using a positive superfat and always use a small superfat in my bath soaps (+3% usually), I also know a slight lye excess (negative superfat) is not the "kiss of death" to a soap. A longer cure time can solve the problem, for example. It's just KNOWING what to do that makes the difference. If a person doesn't know what to do, then they often fear that unknown, which is stressful and not Fun Soaping. :)
 

newtosoap101

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Ah I see. So coconut oil wouldn't be left in the soap if you have a true 0% superfat (and everything goes according to plan), but the fatty acid that is made when coconut oil is used cleans clothes better. That makes sense. I think I will make a 100% coconut oil batch and then use a bar of that and a bar of the crisco soap every time I make laundry powder.

Well I woke up this morning and the crisco soap is still way too soft. I think I put too little lye in after all. I melted it down in a bit of water and then added another ounce of lye dissolved in a bit more water. I was worried it wouldn't melt, but it's looking like mashed potatoes now so I think that's a good sign. I'll test for a zap in a few minutes. I'm going to let it cook a while too so it dries out some. Luckily it doesn't matter too much if that bar isn't that hard since I am just grating it up, not using it in the shower. Although I've read soaps that have too much water can get moldy. Hopefully that won't happen. I don't really know what I'm doing, but I'm still having fun!
 

DeeAnna

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"... it's looking like mashed potatoes now so I think that's a good sign. I'll test for a zap in a few minutes...."

Oh, goodness, I don't think I'd do that if I were you. Let the mixture sit for a day or two THEN test.
 

newtosoap101

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lol too late! It was a bit zappy. Maybe I did add too much lye. I was reading this post about rebatching and the author said to let it cook in the crockpot for 4+ hours. How come it takes so much longer the second time? It's been cooking 2+ hours now and is still zappy.

I've been reading that people use lye heavy soap for laundry anyways so even if I added too much I think it's still OK to use for that purpose, right?
 

kchaystack

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Lye heavy soap does eventually sort itself out usually. The caustic eventually reacts with the CO2 in the air to create soda ash. I would mold it and cut it, and then grate it and lay it out to finish drying for a couple weeks.
 

DeeAnna

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The reason why your soap is staying zappy longer than you expect may be due to these things --

(1) saponification is going to slow down as the fat content drops and the soap content rises
(think of it like this -- the lye has to hunt through all that finished soap to find fat to react with)
and/or
(2) you may have more lye in your cook pot than is strictly needed to saponify the fat remaining.

In either case, my personal opinion is get the soap nicely warm and fluid, add the lye, cook for maybe 1/2 to 1 hour, get the soap into the mold, and give it plenty of time to finish saponifying at room temp in the mold. If you want to hurry things along, of course you can cook it for multiple hours before molding -- there's nothing really wrong with that idea -- but there's the risk of drying the soap out as water evaporates.

Edit: If you want to grate the cooled, molded soap right away, as KC suggests, I'd wear gloves to protect your hands from any excess lye.

As far as lye heavy soap for laundry -- yes, that's true that some people do that. Also you'll find that a modest amount of excess lye will disappear during cure, so soap that started out as slightly lye heavy will be fine in some weeks.
 
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