Introduction: Soap With Used Cooking Oil

Picture of Soap With Used Cooking Oil

Easy and cheap way of making soap.
Avoid the obstruction of kitchen pipes and the polution made by the used cooking oil!

Step 1: Materials

Picture of Materials

You will need this materials to make a good home made soap.

Step 2: Soap Recipe and Fabrication

Picture of Soap Recipe and Fabrication

First I will give you the base recipe for one liter of used cooking oil.

1 liter of used cooking oil
200 grammes of caustic soda (NaOH)
400 milliliters of warm water
40 milliliters of softener for clothes

1. mesure the cooking oil and put on a recipient after filtering impurities out
2. mesure the water
3. weight the caustic soda
4. dissolve the caustic soda with the water (use mask, glasses and protection gloves because the mixture will boil and release toxic gases)
5. join the mixture with the oil
6. stir 15 minutes with a wooden spoon, until the prepared becomes consistent and put the softener for clothes to give the soap softness and fragrance

Step 3: Final Preparations

Picture of Final Preparations

Put the soap in diferent recipient and let it dry two days. You will see when you can take it out of the containers when we turns white.

Let it curate two weeks, the soap will turn much more soften.


travcoman45 (author)2012-04-15

Does this soap ever come "trace" stage? I've tried 3 batch's and it never seems to be right. I've measured everything very carefully and it just doesn't come out right.

keriksen1 (author)travcoman452017-10-06

Did you use pure NaOH? A lot of houshold products contains much sodium carbonate and that won't work...

travcoman45 (author)keriksen12017-10-06

Yes is was pure NaOH. I make a fair amount of lye and pine tar soap. Never a problem with those. This just does not work out for me.

doxielover4ever (author)2013-07-02

Hate to say it, but doesn't laundry softener contain ground up glass? Or am I getting it mixed up with laundry detergent? Either way, I would hate to be eating or washing with glass!!!!

Laundry soap and detergent do not contain glass. That would be illegal and be a massive recall.

doxielover4ever, kindly please let me know where you heard that laundry softener or detergent contains ground up glass? That is the biggest load of nonsense.

The ONLY use for ground up glass in any cleaning product would be in a metal polish, and even then silica is used, not glass as such.

The only thing used in SOME laundry detergents is Sodium Metasilicate Pentahydrate, otherwise known as Liquid Glass or Waterglass.

So no, it doesn't contain ground up glass, and I'm in the chemical manufacturing industry.

susanna.kisa (author)2014-11-22

My soap is curing , I tried a bit but it was very burning ,is that because the soap didnt stand for 2 weeks , and das it loose is that sting later?

Soap needs to cure for 4-6 weeks. Some up to 8 depending on water content and how muxh soft oils used.

Hi Susanna. Maybe a bit late of a reply, but perhaps others like to know too. If the soap burns that means the pH is too high still. Either you have added too much caustic soda, or the reaction between the caustic soda and the oil isnt finished yet. I think it is probably the latter, as I normally take a month to cure my soap, so 2 weeks might be a bit short.

cdmc198 made it! (author)2014-09-19

i don't know about positive. more of a warning. a lot of these recipe don't say why you should not mix with tap water they just tell you not to. well im not sure there may be a unknown factors i am unaware of but yesterday i made this recipe and it blew up or volcanoed on the stove. i put my distilled bottle water in my pan added my lye a little at a time and about 1 to 1 1/2 seconds after i added the last bit of lye the pot went up now the only thing i can think of is the Teflon in the aluminum pot had some ware and the lye water reacted with the aluminum. beware of the aluminum. i only use glass ware and stainless steel from now on. any one feel free to chime in or pass this on. maybe i am wrong maybe it was some other unknown factor? as you can see the was a dark gray to a brown and almost all the teflon is now gone. super clean pot though minus the glitter like metal flake i had to clean up after.

pdehart torres (author)cdmc1982017-07-23

Using purified water is ideal instead of tap because of the minerals and iron that are often in city and well water can react with your soap causing any number of unfavorable problems. Use stainless steel pots to prevent damage to your kitchen and soap batter plus aluminum dose not play well with lye! As for the soap blowing up, aside from the aluminum reaction it may have volcanoed on you due to exothermic reactions and needs to be stirred frequently to release the heat building up. I would also not recommend using fabric softener in a soap recipe. It is not made for soap it is for the washing machine. Also, run all recipes through a lye calculator. Bramble berry, Green mountain sage and soapee (my favorite) are all good options.

pingh2 (author)cdmc1982016-03-29

Yes, never use aluminum pot, it will react with NaOH violently. Glass-made or heat-intolerant containers should also be avoided.

Use stainless steel containers or PP containers seems fine. Tap waters is actually OK though.

BrianN64 (author)2016-08-14

Many thanks for the recipe--my first experience with soap making. A number of things went wrong during the procedure and the mixture solidified into a very hot orange, flaking, putty that had to be pressed into the mold rather than poured, possibly due to too much caustic soda . In any case had fun and vow the next batch will be better.

noel.keen (author)2016-02-22

Can't understand half these instructions. The English is not correct.

FotiniL (author)2015-10-12

I just tried making my first batch ... Let's see how it turns out ...

Just one possible problem -- when I poured my batch to set in the mold, it still seemed alittle something between watery and oily in some places (especially corners) ... Is this to be expected and will it dry away ??? If it isn't the desired result, should I have used alittle more lye or alittle less water and oil ???

Sure would appreciate input !!!

MangS1 (author)2015-04-23

Very nice video and great recipe i use it myself, just make adjustments for adding some Borax for extra suds or any frangrances and colors.

Any kind of soap that you have made or make using Lye needs to cured for at least 6 weeks or it will burn your skin. 6 to 8 weeks is best. Lye soap is still the best soap to use for general cleaning hands or body, but i wouldnt use it on your hair its a bit harsh to the hair.

susanna.kisa (author)2014-11-12

Hi there!

I just made the soap form the oils ,Well I love it ,made 2 batch one with lavender and one with lemongrass fragrance ,still warm ,so I cant use it just jet ,but I be making one lot every day ,I got at least 10 litters of fresh oil . thank you for posting

christina.c.andrade (author)2014-08-22

Would the soap be better suited to use on the body if there were no fabric softener?

loisdenise (author)2014-02-11

For filtering waste grease: if your grease is not fully liquid warm it just until it is. We don't need any grease burns here! Pour the grease through a seive lined with a filter of some sort. Coffee filters, paper towels and scraps of fabric work. I saw a demonstration of old fashioned soap making using unfiltered soap. The daughter said they would find bits of crispy pork fat in their bath soap.

loisdenise (author)2014-02-10

Thankyou for the recipe for used cooking oil.

One caution: lye (caustic soda) should never be put in hot water. Use very cold water instead of warm. It will still get very hot as the water and lye react.

slearner (author)2013-09-19


I have been using WVO for years in my car and have recently tried making soap with it. It worked out great. I just used the cold process with a basic recipe with a bout 25% coconut oil (76 deg). I tested and started using it within three days and it has great cleaning power and is not harsh. Can't wait to see what it is like after some curing time. It had no "used cooking oil smell" after it was processed.
I have a question I can't find an answer for by other internet searches:
Since I collect oil from several restaurants the oil is not consistent. How would I do a titration on it to find out how much lye to use All the soap calculators assume you know the type of oil you are using.

Thanks Gang



tonygoffe (author)2013-03-08

...NOW...if someone could just do an Instructable on "How to make a Soap Mold/Press" ..we'd be in Heaven !!!!!!!

mh1688 (author)2009-09-17

To recycle the cooking/frying oils into household cleaning soaps is the long exist process in Asian countries for many generations. This is an ecological method of reducing environment pollution and was published by United Nation Civil Society of Brazilian Foundation of America.


Since the oil has been break down due to the extended high temperature cycles, the trace of cold process soapmaking starts immediate after the oil combines with lye water. You can use the lemongrass or lavender infused water in this process to eliminate the light oily smell. The soap will be ready after 3 weeks of curing. The PH should be at 8 or less. It is safe for your skin.

We have produced the eco-friendly soap with the oils that we collected from neighbourhood restaurants for charity fund raising. The cleaning power is extremely strong. On top of that, this soap is enriched with natural glycerin that was produced by the natural saponification process. It helps your skin to retain moisture after you use it. Your skin won't feel dry or cracked.

Due to the nature of the oil, this soap is not recommended to use on your body or on your pet. You can use it to clean your dishes, oven, stoves, laundry, floors and any other household cleaning. You also can make liquid soap with it by thread the soap then add one part of hot lavender infused water and 2 part of hot water. Stir gently, let stand 30 minutes then stir again. Let stand overnight then gently stir again. It can replace your hand liquid soap, kitchen dish detergent and laundry detergent.

craziedde (author)mh16882013-01-23

I was thinking to pickup some wasted soy bean oil from local chines restaurant.
But was hesitating as its pretty highly heated and over cooked.
Do you think I should try?
Also my first experiment with my cooked chicken fat was a little off ( come a little to high on PH but that could be just me putting a little to much KOH )

Davidrichard (author)2012-11-22

Hi to all,I am new person to the blog.I want to share about the cooking oil in the online industry.Keep update the blog.

grease recycling bin

wolfsingleton (author)2009-06-15

My wife does a very similar method, but she scents the oil itself before reusing. If you plan ahead and have a dedicated vessel for the oil, place your 'scent' in the bottom before dumping in the hot oil. My wife collects lilacs from the yard and puts about one big handful of torn off petals into a 5 gallon bucket then fills it about 3/4 with warm oil and then adds another handful of lilac petals. Cover the bucket and slosh around a few minutes before allowing to sit for a couple of days. When you filter, the leaves come out but the smell remains! We have also had some success using orange juice or peppermint leaves, but other options haven't come out too well. Hope this helps with the scenting issue for those wanting to keep it natural. Keep up the great work.

Useful information thanks. I've been making an 'enfleurage ' (I think...) using old veg oil and rosemary. Shake often, filter and refresh the rosemary every two or three days. I'm rather pleased with the results, a nice tangy scented oil. Delighted to read of your wife's mint and lilac scented oils so these are next on my list.

Oops, forgot my manners.... Thanks for the original 'bile to vitorgil too. Very informative and helpful.

kibrun (author)2012-02-10

Thanks. Great stuff. Already tried it but i found that the pH is quite high - around 10 to 11 using a pH paper. I made my soap using half of the quantity of the listed materials. The soap is really hard to come off from my hand compared to regular soap. It saves me from buying soap but I need extra amount of water to clear it off. Any suggestion to make it less "soapy" ?

one_fake_user (author)kibrun2012-04-02

Sounds like the NaOH quantity is off. If it feels soapy then more oil needs to be added, particularly if the pH is so high, NaOH is an alkaline substance. That soapy feeling is actually the NaOH turning the fat in the cell walls of your skin into soap, enjoy! :D. Don't worry though, either way the soapy feeling will go. Because you will either have no skin left, or the pH balance has been corrected ;)

kibrun (author)one_fake_user2012-04-02

Yeah, i think you're right. In the next batch i reduced my NaOH by 10%. Still give me a good soap :) I think we can make do with this recipe, it is up to the individual to make adjustment to him/ her liking. In my case, maybe the quality of oil that I used, and maybe the quality of my NaOH ( i bought it from a very remote hardware store somewhere in a suburban area 90km from my home). This stuff is already illegal to the public (in raw form) in my country because they said somebody can make some kind of ecstacy drug or something with it.

The soap is good though. I'm using them to wash my dishes. Thanks Vitorgil :)

AmyLuthien (author)2009-12-10

"1. mesure the cooking oil and put on a recipient after filtering impurities out"
What is a recipient?

xerofdv (author)AmyLuthien2012-01-23


soapwytch (author)2009-09-16

Soap made with lye should be cured a MINIMUM of 4 weeks before using on your body. Old, used oils should not be used to make soap unless it's for laundry soap and even then it would be iffy because the oils will go rancid. Unless it was just for an experiment I would never suggest using "used" oil for soap making.

jennivie (author)soapwytch2012-01-01

If you're making cold process soap then yes 4 to 6 weeks to cure the soap, but if you make hot process soap it can be used as soon as it hardens.

dggriffi (author)soapwytch2010-03-16

using used vegetable oil for soap is common and just fine.  Impurities should be filtered out before the process begins.

nubiana str (author)2010-05-07

how do you filter the used cooking oil? Also, did it smell like fish or chicken in soap form?

vitorgil (author)nubiana str2011-06-26

Fish can be hard, but the caustic soda will take almost any smell.

alchristinechan (author)2010-08-28

in following this soap making process, what kind of soap will it produce? laundry soap or soap for the body? just wondering. :)

vitorgil (author)alchristinechan2011-06-26

It´s more indicated to wash your hands or the laundry. I like to paint usually I use it to clean the brushes it works perfectly.

geta (author)2010-12-05

Eu am inteles ca daca a pus balsam de haine inseamna ca este pentru rufe .

s.g. (author)2010-07-27

what type of oil are u using? and specifically, what is the use of this soap? is it for laundry or is it a hypoallergenic soap? thnk u very much! :))

Bretzielovesjedi28 (author)2010-01-19

question....Y my soap doesn't turn turns brown???

Darcy777 (author)2009-08-13

Friendly note to the readers. ALWAYS pour the lye crystals into the water and not the other way around - for safety reasons. It is shown correctly but I wanted to really emphasize this. If the lye in the water becomes a hard clump, no worries, GENTLY keep stirring and it will dissolve.

sam12587 (author)2009-06-25

Does it just pop out of those accurate cups after curing?? And can you just slice it up like a cake from that cat box or do you need to pop it out first? I might try this and I just want to make sure I understand the whole process & don't destroy my soap at the end :-)

vitorgil (author)sam125872009-06-27

Yes it's easy to pop out of the cups, you can do since you feel the soap have become solid then slice it.

dchall8 (author)2009-06-17

If you are trying this in the US, find a recipe in ounces and pounds before you try it. Soap is a relatively safe chemistry experiment that can go dangerously wrong if you make one simple mistake. Caustic soda (sodium hydroxide or lye) is not something to play around with.

lemonie (author)2009-06-11

Bacon-aroma soap? L

vitorgil (author)lemonie2009-06-11

No way it will smell like real soap. Just try it!

lemonie (author)vitorgil2009-06-11

Thanks - I actually want to make bio-diesel, but I might try it. You don't mention adding any fragrance, so I imagine the smell is just "soapy"? L

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