# My used cooking oil soap experiment



## galaxyMLP (Apr 9, 2015)

So I wanted to use used cooking oil to make soap. Not that I thought it would make a fantastic bar but that it would help keep the oil out of landfills and the drain since most consumers (not companies) don't have a way to dispose of it.

My fear of course is that it will go rancid in a matter of a few months. I read that 100% saponified oils will not go rancid so I came up with a way to use the oil.

First, I cleaned the oil by filtering it and "washing" it with water and salt. This got rid of most of the smell. All that was left was the cooked fry/bread smell. Thank god the fish smell went away. 

Then I used this recipe: HP

70% canola (this was the cooking oil)
16% coconut
14% lard

4% lye excess

5% mango butter SF

I was a little ambitious and used all 91 oz of used oil that I had gotten (for free from some locals in my community). I don't really know what possessed me to do that. It made almost 12 lbs of soap!! [emoji20] 

I ended up having a full to the brim crock pot (which of course I spilled a small amount of raw batter out of...) 

After the cook, I tested the soap. I wanted to make sure it zapped, it did. I cooked it a little extra to be sure, tested it, and it zapped again. Then I added the mango butter and cooked. Did the zap test, no zap! Yay. 

I did not scent about 8 lbs worth of it. But I scented ~3 lbs with almond and vanilla. Its cooling now and I'll photograph when I unmold it!

I will be donating a bar of the scented soap to the person who gave me the oil and the other 8 lbs will be left to sit for 6 months for rancidity testing. Woo.


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## The Efficacious Gentleman (Apr 9, 2015)

The soap will then have a SF lower than 5% as the lye excess will of course take a chunk out of the mango butter.  Will be interesting to see how it ages as it was used oil in the main.


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## galaxyMLP (Apr 9, 2015)

Yes, it should be a 1% SF by calculation. Of course, I'm not sure how pure my lye was and that's why I did a 4% excess since most lye is between 90-100% pure. I wanted to be sure that all of the canola would be saponified. I think a 1% SF (ish) will be sufficient as the bar ages. I look forward to seeing if this will work. I'd love to donate these soaps (if they don't go rancid) to a local shelter for women and children of domestic violence.

Eta: I also wanted 20% lard and 10% coconut originally but I didn't have enough lard on hand for that... So I adjusted accordingly! And if this does work, I'll be tweaking the recipe and adding castor oil for da bubbles!

Here's the unmolded soap. The lower layer should turn dark brown whereas the upper layer will be tan. Keyword: should


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## Trix (Apr 9, 2015)

Wha a brilliant way to reuse cooking oils so it doesn't end in landfills. some ppl use it as biofuel to....but the soap from recycled oil idea is even better  
Well done!


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## dosco (Apr 9, 2015)

Seems to me that used/nasty cooking oil might be a good candidate for the "massive excess lye" type soap described here as -40% SF Andalusian castile.

I'm thinking of doing using this method with about 6 gallons of spent fryer oil (used for frying Thanksgiving turkeys).

My electronic scale is messed up - need to get that fixed first.   

-Dave


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## galaxyMLP (Apr 9, 2015)

I read through quite a bit of that. I was originally thinking of just doing about a 5% lye excess and not adding a SF but I decided to go the slight SF route. I'll be experimenting with just the lye excess (and a smaller batch) with my next delivery of used cooking oil.


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## MetalManiac (Apr 9, 2015)

The soaps you made look great! I'm a big fan of used cooking oil for laundry soap. That was the entire reason I decided to make my first batch of soap three years ago. I now make laundry soap with 10% coconut, 20% lard and 70% used peanut oil (and the occasional canola or corn). Kudos to you for being "green" and turning waste into a good product.


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## zolveria (Apr 10, 2015)

I was once told by a person that mcdonald and places may give you there old oil. if you ask. same for Starbucks if you need coffee grinds for you garden of soap projects.


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## dosco (Apr 10, 2015)

zolveria said:


> same for Starbucks if you need coffee grinds for you garden of soap projects.




Or if you need some material for your compost pile!



-Dave


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## galaxyMLP (Apr 11, 2015)

If this experiment ends up working out, I'll have to check out my local mcdonalds or other fast food!

Its weird though, the unscented soap actually smells better today than it did when I first made it and it was cooling in the mold. It has no detectable smell now. When I first made it, it smelled "soapy" and kinda oily.


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## galaxyMLP (Jul 7, 2015)

Update! It has now been almost 3 months. They are nice and hard and (mostly) white. A few have developed DOS in one spot. They all still smell great. 

They were down stairs for the first 2 months. About 3 weeks ago I moved them upstairs for more space. (None had DOS at this point)

A week after I moved them up stairs and they went through one REALLY hot day where my ac went out. It probably got 95+ up there with really high humidity (think swampy Florida!)

 I think if I had kept them downstairs where it never got above 82, they may not have developed DOS. 

At this point I'm very satisfied with my experiment and I think these will make great "donation" soaps. I want to add a "buy one soap donate one to a local shelter" kind of thing and I want to use re-claimed oil for it. 

Also, my boyfriend loves it. Go figure, he doesn't like any of the "good" soaps, says they dry him out, but he loves this one... Maybe I should try it. He also loves that they smell like Almond. Mmmm.

And by try it, I mean on my body. I used it as a dish cleaning soap and on my hands and it worked really well. It also lasts FOREVER. It's very strange.


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## KristaY (Jul 8, 2015)

So if you go to a fast food place and they give you spent oil, will it always be just a specific type of oil or a blend of various used oils? I'm just wondering if it's a blend, how would you calculate the SAP value?

What a great way to use up oils that would go to waste, galaxy! I have a particular soft spot for abuse shelters (I work for one) so that makes it even better. Help the environment, help your community. Awesome work!


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## galaxyMLP (Jul 8, 2015)

Aww thanks! I intend on asking what the blend of oils is. It is usually soy or canola. Because this was done with canola and I had good results I plan on seeking out places/people with canola oil. I may try a soy experiment in the future. They are quite similar though.


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## DeeAnna (Jul 8, 2015)

If it's a blend, compare the SAP values for the various oils in the blend. A lot of times they will be pretty similar. That means even if you don't know the actual % of each oil in the blend, you can usually make a pretty safe guess.

More info on using stale or rancid oil in soap: 
http://handmadesoapcoach.com/dont-throw-out-that-rancid-oil-make-soap/
http://www.soapmakingforum.com/showthread.php?t=35031
http://www.soapmakingforum.com/showthread.php?t=35257
www.soapmakingforum.com/showthread.php?t=32717


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## not_ally (Jul 8, 2015)

That is interesting, K, and a great way to conserve.  Also, even if a batch does get DOS-y, the good thing is that there is so little invested in terms of resources (except your time, of course), and if you have to throw it away you are not really wasting anything.

ETA: It does kind of crack me up that *these* ended up being your bf's favorites with so many choices!  Go figure


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## galaxyMLP (Jul 8, 2015)

DeeAnna said:


> If it's a blend, compare the SAP values for the various oils in the blend. A lot of times they will be pretty similar. That means even if you don't know the actual % of each oil in the blend, you can usually make a pretty safe guess.
> 
> More info on using stale or rancid oil in soap:
> http://handmadesoapcoach.com/dont-throw-out-that-rancid-oil-make-soap/
> ...



DeeAnna, you wrote this on one of those threads:

"All these chemicals have varying degrees of odor. The odor from the fatty acids will disappear during saponification, but the odor from the aldehydes and ketones will remain in the finished soap, since they do not saponify.

One of the other interesting things I gathered from this book is that an excessive amount of free fatty acids can cause ricing, especially if the ricing occurs right after the lye solution is added to the fats. The fatty acids react instantly with the lye and create the ricing effect. (Ricing from fragrances and other additives is another story.) So even if an oil doesn't smell rancid, it may still have excessive free fatty acids and may rice."

I was actually fearful of this when making this first batch. I read about this on wikepedia (about ketones and aldehydes). I also happened to have read almost all of these websites before trying this. Thank you so much for adding these because it will explain to someone else coming along after me why I did, what I did. You always provide so many great links! 

And yes, most oil blends usually have similar sap value oils (like typical vegetable oil is often a blend of canola, soy and light olive. [So I've read]). 

My oils did not smell rancid in this case they were just "well used" and had various food smells.


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## Amarae (Sep 29, 2018)

Obviously I’m pretty late to this thread but I’m just in love with this project. I though I had thought of it first- but it seems you have already nailed it! So, I want to do this same thing, but with doughnut shop fat. Please connect with me, I need a guru, and there’s tons of stinky locals that will appreciate it. Plus, the earth is pretty cool too. I like saving it.


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## Habibah (Sep 30, 2018)

I love to learn and you guys are a university. I make my household cleaning soap, which I don't sell. Don't know why, but I love the idea of using my used oil.
A dumb question, what is ricing?


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## DeeAnna (Sep 30, 2018)

Ricing is when the lye reacts extra fast with some of the other ingredients in your soap pot. The result looks something like badly curdled milk or watery cooked rice. 

Ricing can be a warning that the soap batter might become "soap on a stick." That's the entire contents of the soap pot get so thick so fast that it can literally trap your stick blender or spoon in the hardened soap. When this happens, some people try to glop it in the mold before it gets too hard, but that can be awfully messy. It often works better to switch to a hot process method and finish saponifying the soap in the soap pot. It will typically soften and it's then easier to get the soap in the mold and you might get a better finished appearance.

Other times, the ricing isn't quite so bad and doesn't progress beyond the watery rice stage. In that case, it may be possible to stick blend the batter until smooth and then get it in the mold fast. You don't always know if ricing is going to stay ricing or go into soap-on-a-stick, so it's a bit of a gamble. 

Some fragrances (EOs or FOs) or fats with a high percentage of free fatty acids will cause ricing. I'm sure other things can too, but those are the two that come to mind.


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## TeresaGG (Sep 30, 2018)

Cool. My local McDonald's have a grounds for the ground where they will give you coffee grounds if you ask. I'll have to ask about the oil.


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