Introduction: How to Make Soap

Picture of How to Make Soap

I know this has been done before, but I thought I would document the latest batch of soap I've made. Hopefully this instructable should give you some practical hints as well as help you with the theory of making soap from leftover fat.

Soap makes a unique and personal gift, especially when it is home made. You can also sell your soap at a farmer's market or just use it yourself. And it's a great way to get rid of old grease and fat that would otherwise find it's way to sewers or landfills.

The process uses caustic chemicals, so it is slightly dangerous. But if you follow general safety guidelines and keep your wits you should be fine. You might make a mess, but it should be easy to clean up because most of the spills will be made of soap!

I got most of my info from this page and this lye table

I was inspired by this instructable:

Note: I would've gotten better pictures, but it's hard to use a camera with eye goggles and rubber gloves.

Step 1: Supplies

Picture of Supplies

Ingredients you will need:
1. A lot of animal fat or vegetable oil.
2. I added some olive oil to my recipe to make it milder.
3. Lye (NaOH) crystals. You can get this at the hardware store next to drain openers.
4. Distilled water. You can use tap water, but I wanted to make sure there were no dissolved minerals that could ruin the soap.
5. Essential oils for a scent. This is optional, but I think it helps. I use tea tree oil and jasmine oil. You can find these at a natural foods or drug store.

Tools you will need:
1. Safety equipment: Rubber gloves, goggles, and an OPEN bottle of vinegar withing easy reach, in case you need to neutralize any spilled lye. Lye (NaOH) is very basic and caustic, and it WILL burn your skin, or any part of your body for that matter. If you've ever seen Fight Club than you know what I mean.
2. A large glass or ceramic bowl to mix everything in. Anything that touches lye must be glass, because lye can react with plastic, wood, and especially metal. I was lucky enough to find a big Pyrex bowl in my attic that an old roommate left behind.
3. An accurate scale. It doesn't matter whether you measure in grams or ounces, but you must be accurate. I have a digital scale that works in grams or ounces.
4. Something to stir with. You can always just use a big spoon, but it will take a long time and you will get tired quickly. I got a stick blender at Goodwill for a couple dollars that worked well until the motor burned out. So for my second batch I just pulled it apart and mounted the business end to a power drill. Make sure that whatever you use for mixing, you wash it very well before using it on food. I have dedicated equipment that I use for mixing soap and nothing else.
5. Some kind of mold to pour the finished soap into. Besides a casserole pan or plastic bin, you can also use lengths of PVC, or paper cups to mold the soap into round shapes (see the main photo).
6. Notepad and pen along with a calculator to make conversions.
7. You will also need a few more tools like bowls and scrapers etc.

Lay down some newspaper on a big table or counterspace. You will need plenty of room to make soap.

Step 2: Obtain Clean Rendered Fat

Picture of Obtain Clean Rendered Fat

To make soap, you need some kind of fat or oil. Vegetable oil will make a softer soap than saturated fat like lard or shortening, so it's a matter of personal preference of whether you like a hard bar soap or a somewhat squishier soap. Blending several kinds of oil or fat together can give you a wide variety of characteristics.

Some commenters have pointed out that vegan (and therefore kosher and halal) soap can be made with only vegetable fats. Check out SoapyHollow's profile for vegetable oil recipes.

I got my fat mostly from bacon and hamburger drippings, with some olive oil too. It is important to make sure that you have each kind of fat separated and pure; i.e., don't mix beef tallow and lard together until after you have weighed them, or else it will throw off your calculations and your soap will not turn out right. Then you must render and clean the fat. Rendering is the process of melting the fat to separate it from water or bits of meat. In my case, I just fried my bacon and poured off the extra grease into a jar.

To clean the fat, you can either boil it, filter it, or both. I first filtered everything through an old sock and a coffee filter in a funnel that I made by punching a hole in a plastic cup. Then I boiled it in a big tall pot with half water and half fat. This gets rid of any water-soluble dirt or salt left in the fat. Boil it for about 20 minutes, then cover and let it cool (in a fridge or outside in the winter) until the fat floats to the top and solidifies. Then you can scoop out the purified fat and throw away the nasty water at the bottom. Scrape any dirt off the bottom of the fat.

Step 3: Make Measurements and Calculations

Picture of Make Measurements and Calculations

A big part of making soap is being precise. You need to weigh out ingredients precisely so you have them in the right proportions. Never measure by volume.

First weigh the containers you will put the fat into, then weigh out the fat. I measured 1626 grams for the bowl and the fat, then subtracted 906 g for the Pyrex bowl, leaving 720 grams of fat. I also measured out 102 grams of olive oil in another cup and added that to the rest of the fat for a total of 822 grams of fat.

In order to use the right amount of lye and water, you need a table of saponification values. You can find one set here:

You can also use this online lye calculator:

Since I am aiming for 5% residual fat at the end, I used values of 0.132 for lard, 0.129 for olive oil, and 0.38 for measuring the water.

720 g lard x 0.132 = 95 g NaOH
102 g olive oil x 0.129 = 14.2 g NaOH
Total: 108.2 g NaOH
Now is a good time to put on your gloves and goggles. Weigh out the lye crystals into a bowl. It is OK to use plastic at this point because the crystals aren't wet.

822 g of total fat x 0.38 = 312.4 g water.
On this last measurement you don't need to be too accurate. Just add a little extra water if you're not sure, since it will mostly evaporate in the end. Put the water in a smaller glass bowl so you can mix the lye in. I used a coffee pot because it is made of glass and has a pour spout.

Now CAREFULLY and SLOWLY add the lye to the water. NEVER add water to lye, because it can spit out of the container and burn you. Stir slowly as you add the lye, making sure to dissolve all the crystals. The water will heat up, but if you mix it slowly enough it won't heat up too much.

Step 4: Mix Lye and Fat to Make Soap!

Picture of Mix Lye and Fat to Make Soap!

Now comes the part where you actually make the soap. Keep your safety goggles and gloves on, because there is still a risk of chemicals splattering.

Make sure that both the fat and the lye/water mixture are warm, about 100F. This will keep the fat from solidifying before it actually turns into soap.

While stirring, slowly pour the lye/water mixture into the fat. The fat will start to turn milky and thick as you stir. If you're using a blender this step will go much quicker.

Once the soap is the thickness of pudding, test whether it is ready by trying to leave a "trace." Drip a trail from the spoon onto the surface of the soap. If it leaves a trail for a few seconds, that means it has "traced" and is ready to be molded. If the trail quickly drops back under the surface it isn't ready and you need to stir it more. Keep the mixture warm, and remember that you can't really stir it too much.

After it has traced, you can add whatever scent you want. You can also add ground spices or herbs. I added some nutmeg, ginger, and orange zest (mostly because that's all I had around). Just don't add anything really scratchy like coffee grounds, since you will end up making sand paper out of your soap. I learned that one the hard way! Also don't add anything with alcohol, acid, or any chemicals that might throw off the reaction.

You can now pour the soap into whatever mold you want. I used a simple casserole dish. After it solidifies (this takes a few hours or overnight) you can cut it into bars and wrap it. It's good to keep most of the air away from the soap while it cures to prevent carbonic acid from forming on the surface. This can happen due to a reaction with carbon dioxide in the air. Plastic wrap or wax paper works well for this. You can also imprint a brand or logo into the soap while it is still soft.

Now you have to wait. It takes about 3 weeks for soap to fully cure. During this time, any excess lye will reacting with any remaining fat. If you use the soap before this time, it could irritate your skin. Use this time to read a book or take up another hobby, like homebrewing (that's my next project).


SHOE0007 made it! (author)2017-04-28

I have made a similar thing but using bought lard fat and heating it with excess nutmeg. Some nutmeg converted into carbon by heat while I used 10-15 g of Potassium Hydroxide 100%. Here one pic in 1 L. I only used half of it and saved the rest for later.

icelandinthesun (author)2011-08-06

I am really interested in making my own soup but i am not sure that i will be able to get Lye (NaOH). Is it necessary or would it be ok to skip it?

Housedog (author)icelandinthesun2012-07-20

If you are indeed making soup, then you should definitely skip the lye!

insightz1 (author)Housedog2017-02-08

Hey Housedog, don't be nasty. It's un-American.

Housedog (author)insightz12017-02-10

I find a lack of a sense of humor to be "unAmerican", but to each their own.
When this instructable was originally posted, the auther made a typo and called it making "soup", not "soap".
So as a silly joke, i recommended not using lye!
Obviously the typo has been corrected. So you then jumped to the conclusion that i am nasty and unAmerican.

ThomasP5 (author)2015-01-13

I found these directions from 1833 on how to make soap.

ThomasP5 (author)2015-01-10

If you are interested in making soap you should checkout

tinyinkling (author)2013-09-11

The Walton Feed soapmaking link has moved. It's now here:

mrmerino (author)2012-07-20

Hey, do I have to make this in an abandoned house?

Rikitiki (author)2012-07-20

This is a good idea.

Calis (author)2009-12-05

Please don't use vinegar to neutralize lye on your skin.  While it will neutralize it, it also causes a chemical reaction that releases a great deal of heat.  This can cause thermal burns on top of your chemical burns.  If you get lye on your skin,  brush it off with a dry gloved hand, or wisk broom get the idea.  Then rinse the area thoroughly with water.

abadfart (author)Calis2010-01-14

his name is Robert Paulson LOL meatloaf  

his name is robert paulsen... his name is robert paulsen...
lol im watching that movie right now.

very nice i use fight club a a test for new girlfriends

cuchulain92 (author)abadfart2011-10-20

HEY! First rule!

that...sounds a little creepy :D

haha well if they like the movie then there chances go up... the girl im seeing right now quoted it the first time we met so i knew she was a good choice

PhylC09 (author)2011-01-13

I also make soap and sell to make extra money and I use good old shortening in 35 lb blocks from restaurant supply. For home purposes, the one pound blocks of shortening or lard works fine. Some shortenings are blends, which also include beef tallow.
It makes a great soap and I like to add other ingredients to make it hard, but it's not necessary for home use. Just make sure to use coconut oil and olive oil (not the extra virgin), it's what makes the soap later well. Here are some links for other info:

Happy Soaping

nax (author)2010-08-27

I almost lost my house cleaning fat yesterday. I'd done the boil it and then scoop off the fat three times, and I was melting the clean fat to make the soap. A bubble of water hit a hot spot in the fat and popped hard. Fat everywhere, including the stove - huge grease fire. I was lucky, the grease fire went out by itself soon after I turned off the heat. Lost about half my fat, which was a coffee can full. Spent most of the day cleaning it off the floor, walls, and ceiling. I am not joking about the ceiling.

discontinuuity (author)nax2010-08-29

Sorry to hear about that. I have an electric stove so I hadn't thought of the fire hazard. I usually boil in a tall stock pot with a lid to minimize any spills or splatter, and melt fat in the microwave.

nax (author)discontinuuity2010-08-29

I probably would have been fine if I had kept stirring. The tall stock pot is a good idea too.

Not so sure about the microwave - I know people who have had candle wax ignite in the microwave. But if you keep the bursts short and pay attention you should be fine.

I tried again the next day using vegetable oil, and it looks fine so far. Still has to age before I know how good it will be.

All's well that ends well. I got divorced the day before the mishap and I felt like I didn't care about anything anymore. Turns out I care quite a bit about flaming death and destruction. Got my emotions back online. Effective, but not recommended.

GorillazMiko (author)2008-01-10

Neat. Looks like messy work kind of, but it's worth it!

It cleans up pretty easily, because all the mess is just soap! Laying newspaper down on your work table helps a lot though.

SoapyHollow (author)2008-07-24

I don't know where you got the idea that vegetable oils can't be used for soap. I've been making vegan safe vegetable soap for years and years. It makes a much better soap than those with animal fats; it lathers better and is better for your skin. (As well as being safe for kosher, halal and vegan lifestyles.) The oldest soap company in the world has been operating in Palestine since the time of Christ, and they make Castille soap, which is olive oil and palm oil. Animal fats in soap are a relatively recent tradition, starting in the early 19th century when large amounts of animal fat were available to the common man. Secondly; NEVER EVER add water to lye. You add lye to the water. Also, using glass for the NaOH and water blend is a bad idea for anything but very small batches. Glass tends to crack. Your best bet is stainless steel all the way around. For the record; coffee grounds make a fabulous addition to soap. You have to grind your own, but my Coffee deodorizing soap is a huge seller. It is significantly better to cure traditional soap in open air, or like we do, in dessication cabinets rather than wrapped, especially using animal fats.

I stand corrected. Some of the links at the top of the page (which now seem to have gone dark) it seems gave me some incorrect information. I'll be editing this instructable to be more accurate, and when I make my next batch of soap (probably some combination of olive/palm/coconut oil), I'll make an instructable about that too.

The only real reason I've been making soap from bacon fat is that it is free and abundant, and makes some pretty good soap. And because I saw this instructable before I made mine.

drawe21 (author)discontinuuity2009-12-31

Waltonfeed web link changed, new one is below.

discontinuuity (author)drawe212010-06-06

Thanks, I updated the link.

Yeah...I didn't mean to sound as bitchy as it does when I re-read it. Soap is a bit of a passion for me, and like all geeks, I get weird about my subject area. ;)

I've got a good small batch recipesmall batch recipe in the instructable that I used to make little "cake" soaps, but the recipe works in any mold. Alternately, I'd be glad to share recipes with you, or help you fine tune something if you ever want any help. :)

Not bitchy at all. I appreciate your knowledge, since most of mine seems to be apocryphal and based on old wives' tales, or something I read once and half remembered. My next batch of soap is still a ways out (I've got other projects to deal with), but I will definitely consult with you before beginning. I would like to make a few pounds to sell at the local organic market, to see if I can make some spare cash from selling soap

I've had a soap company for a long time, and we recently had to stop selling because of insurance issues. There was only one company in the country that would underwrite product liability insurance for small manufacturers at a reasonable price, and they decided that after reviewing the new legislation that is about to impact companies like mine, to more than quadruple the rates...bringing my insurance rates close to what I actually *made* each year.
(here's a link to stuff I've written about the pending federal legislation )


We have yet to be able to find another underwriter, even though there has never, in the history of tort system in the US, ever been a successful claim against a soap manufacturer due to product liability.

But, this being America, land of the courtroom land shark, it's absolutely insane to sell anything without insurance.

I tell you all of that, because liability insurance is one of those things you may want to consider. Without insurance, if someone slips on a bar of soap, and decides to sue you, they can bankrupt you in legal fees alone before a judgment ever gets rendered. All personal assets are up for grab unless you're a corporation, and even then, they can try to attach personal assets of owners and board members. The tort system is crazy and only the lawyers win, really.

The odds of anything happening are really low. But, for me, I couldn't take the chance, so I stopped selling until I can find insurance. Unfortunately, that meant putting everyone who worked for me out of a job too, and then that rolls into my suppliers needing less people and warehouse space, etc.... The system really is stacked against small businesses.

Just something to consider.

dave999 (author)SoapyHollow2009-06-28

please tell me the ingredients for vegan soap my mail id is thanks for your most valuable info

noname420 (author)2010-06-04

LMFAO well Tyler Durden says "Hi." Sorry i saw the warning you are not held responsible for the actions of us and or our imaginary friends to make homemade dynamite is classic. I wonder how many other people got that joke. The first rule of project mayhem is don't talk about project mayhem.

discontinuuity (author)noname4202010-06-06

Sorry, I can't talk about that.

taluntain (author)2010-05-07

would i be able to use fat that a slaughter house just throws in the trash

discontinuuity (author)taluntain2010-05-09

Yes, just be sure that it isn't rotten, and you know what animal it comes from.  Then you will need to cook down all the fat until you get clean lard and use it normally.  Although if the slaughterhouse is throwing it away it might be nasty already.

taluntain (author)discontinuuity2010-05-10

not always i used to work in one and if the cow is to fat they cut off extra fat to make the meat leaner

abadfart (author)2009-05-18

nice fight club joke

grenades_and_ham (author)2008-01-10

good idea. but still either way your reaction is going to heat up. it simple chemistry. there will be a set amount of energy released. now how that amount of energy is dissipated over time would depends on the temperature. but i usually heat my fat up anyways. helps catalyze the reaction.

Yes, you want to keep it warm, since cooling the mixture might make the fats solidify before they've fully reacted.

CherryPie (author)2008-01-11

Anyone know how to do this using wood ash to make your own lye?

mg0930mg (author)discontinuuity2009-01-19

Dead link.

casey321b (author)discontinuuity2008-09-11

it may be my moms crappy comp but i think its a dead link...

NinjaSloth (author)2008-12-08

FIGHT CLUB!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! you use human fat at times to make soap? just curious...

GreenDay (author)2008-01-10

"Now CAREFULLY and SLOWLY add the lye to the water. NEVER add lye to water, because it can spit out of the container and burn you. Stir slowly as you add the lye, making sure to dissolve all the crystals. The water will heat up, but if you do it slowly it won't heat up too much." You say to add the lye to the water, but then you say that you never want to add lye to water :P

casey321b (author)GreenDay2008-09-11

you said never add lye to water XD

discontinuuity (author)GreenDay2008-01-10

Everything should be fixed now.

Pat_Maroney (author)2008-07-12

hehe, FIGHT CLUB. where's the part about removing the layer of glycerin??? Great instructable I'm serious btw......

SoapyHollow (author)Pat_Maroney2008-07-24

Heh, Fight Club stuff aside, traditional soap leaves the glycerin in. That's what makes it feel so rich on the skin. To separate the glycerin requires boiling the soap and then doing some neat tricks with sugar and alcohol. (I make mine in 50 pound batches because it takes the better part of 11 hours to do it.)

moelle (author)2008-05-18

Can you clarify this comment: "Vegetable oil will not make real bar soap by itself." I'm confused. I make my living selling 100% vegetable soaps that I make myself. What do you mean by "real"?

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