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How to Make Soap with Lye

So, here’s the deal. Making cold process soap is pretty universal. Have oils, mix lye into water (NEVER the other way around), mix lye water into oils, blend until just about pudding, pour into molds, and ta-da! You have soap. There’s plenty of recipes out there, but each person has their own recipe.

There are different oils and butters, how much of each is used if multiple oils are used, that sort of thing. How much water to how much lye to how much oils. Everyone has a different recipe. This is the one we use at Sweet Sisters Vegan.

Safety Measures when Making Soap

I have 100% gotten splattered with freshly blended soap and then managed to wipe it onto my face or under my ear. It stings, then burns, but not right away. It will leave you with a sore patch of red skin for a couple days depending on how long it has been left on there before you raced to the sink to scrub it off.

Now, that’s the diluted stuff. Imagine getting the actual lye water on your skin. It’s probably 100 times worse. I admit I’m lucky in the fact that I take care when it comes to my lye water and mixing the two together. I’ve seen it strip the finishing off a wooden table. Thankfully it was the crappy kitchen table rather than the expensive dining room table, but still. I don’t want any of that on my skin, thank you very much.

So, what should you wear when you start making soap. An apron. Not the most essential thing, I know, but as a girl who constantly wears dresses, it saves a lot of money to keep them looking good without faded patches and holes in them.

You should also wear long sleeves and gloves. It can be a bit messy and you don’t want your arm or hand to suddenly feel like they are on fire. Closed toed shoes are also a great option cause you don’t want to have to try to hop to the bathroom.

Some form of goggles or safety glasses to protect your eyes are essential. It also protects your glasses if you wear them. If it can strip the finish off a wood table, imagine what it would do to your very expensive prescription glasses. Also, a face mask as the fumes are just the worst thing. It will make your lungs burn if you inhale so make sure you’re covering your mouth and are doing this in a well ventilated space.

Why Make it?

If it is so dangerous, then why do it? Have you ever gone to the store and picked up a bar of “soap” and looked at the ingredients? Yeah, that’s not soap. According to the FDA in order for your product to be soap it must meet three basic requirements.

  1. What it is made of.
    1. mainly alkali salts of fatty acids.
      1. Or, the combination of fatty acids with an alkali (ex. oils and lye).
  2. What ingredients make it cleansing.
    1. the alkali salts of fatty acids is the only thing that result’s in the product’s cleansing action.
  3. How it is intended to be used.
    1. It has to be labeled and marketed for use as soap.

This is one of the many reasons why the stuff you see at stores are called “beauty bars” or “cleansing bars”. They don’t meet the very first requirement to be called a soap. They use synthetic detergents to create the cleansing properties in these bars.

Let’s talk glycerin. It’s the leftover oil components in soap. It’s what makes soap moisturizing. Most companies actually take out the glycerin that’s made in these bars and add it to lotions so you have to buy 2 things rather than just one.

Sneaky, huh? Which is why I started making it at home, for myself. I get to reap the rewards of having a single product that I can use and I made it myself.

Do I still use lotion? Yes. We make lotion bars and they work wonders. Especially after stepping out of the shower. I only hit my problem areas where I get super dry skin.

So, What Do You Use in Your Soap?

In a single pound batch of soap we use:

  • 10 oz. olive oil
  • 3 oz. grape seed oil
  • 1 oz. Shea butter
  • 1 oz. cocoa butter
  • 1 oz. mango butter
  • 3-4 oz. distilled water
  • 56-57 g sodium hydroxide (lye)

We wanted a soap that was super hydrating as well as cleansing. This soap does lather, but not as much as other soaps. Since we strive to be as allergen friendly as possible we don’t use any coconut or nut oils or butters.

We prefer to use distilled water so there are as few contaminants in it as possible. The lye is measured in grams to be more exact in our measurements since it is that component that actually makes the soap

Now, let’s talk “superfats”. Superfats are the fats that are left over after the lye has done it is thing. It’s what makes soap so moisturizing. This can be anything from 1% all the way up to 20%. 1-4% are considered to harsh for our skins. I plan to make a 1% olive oil soap which will get turned into detergent for my clothes. 5-8% is the range that is suitable for skin and also creates a hard soap. 9% and up are also suitable for skin, but creates a softer soap since there are a lot of excess oils left over.

Our soap sits between 8 and 9%. So it is hydrating while also making a bar that isn’t really hard, but isn’t falling apart either.

How Do you Make Soap, Then?

Other things you will need before your begin:

  • 1 large bowl for mixing everything together
  • 1 smaller heatproof/resistant bowl for measuring your water and mixing your lye into
  • 1 small, completely dry bowl for measuring your lye
  • 1 whisk/wooden spoon that will only be used for soap
  • 1 silicone spatula that will only be used for soap
  • Something to dump your soap into
    • We use silicone soap molds
    • If that’s not your thing then a heat-resistant glass baking dish with plastic wrap in it will work just fine
  • Some form of thermometer to measure the heat of your lye/oils
  • A hand/stick blender – it should be only used for soap, but I’ve read other people being a-okay with using theirs for soap and then food. I just have never wanted to risk possibly poisoning myself or my loved ones.
  • A kitchen scale

First, make sure you are in a well ventilated space with plenty of working room. If ruining your table or counter isn’t an option either cover them with old tablecloths that you don’t mind ruining, newspaper, or trash can liners.

Second, make sure you have all your stuff out and ready to go. It’s the worst to get into the middle of something and realize that the one thing you need is the one thing you don’t have.

Third, put on all of your protective gear. Make sure you have a sink nearby just in case any accidents occur and I’ve been told that white vinegar helps neutralize the lye, but I’ve never had to do this myself, so you should be good.

Alright now you can make the soap. There are a couple different ways to do this, but the basis is simple. For us, we don’t want to add the lye and oils together if they are both over 110 degrees. We don’t mind tracing them at lower temperatures, and in fact we prefer it.


  1. Measure out the lye – this should be done in a completely dry bowl so it doesn’t activate until we want it to.
  2. Measure the water
  3. Combine the lye into the water and whisk until dissolved
    1. The water should never be combined with the lye as it may set off a chain reaction that could cause the lye to explode and that would be a disaster for yourself no matter how much protective gear you are wearing.
    2. There will be fumes, it will smell, and the lye and water does heat up very rapidly. It can get so hot that it can boil. BE VERY CAREFUL.
  4. Place lye water in freezer for 5-10 minutes to cool. Please extend the cool time if you are making larger batches.
  5. Measure and melt solid butters. This can be done by shoving it in the microwave for 30 second intervals until completely melted, or using a double boiler on the stove.
  6. Measure and add in liquid oils.
  7. Pull the lye out of the freezer and check the temperature.
  8. When under 110 degrees go ahead and add the lye water to the oils.
  9. Blend with a stick blender until trace forms.
    1. Trace is a thickening process in which you can see drops of liquid being held up by the base liquid.
    2. I honestly just pull my stick blender straight up and if I can see the outline of my blender then I’m good to go.
  10. Pour into mold and put in a dark place, preferably a cupboard that doesn’t get opened or the oven if you don’t use plan to use it in the next 24 hours.
  11. Wait roughly 24 hours.
  12. Un-mold your soap and cut into bars
  13. Then wait a very long 4 weeks for the soap to fully cure (we sometimes package at 3 ½ weeks depending on if we are in a time crunch)

At the end of that 4 week wait period you will have soap. Our 1 lb. batch makes about 6 bars of soap, so it will last for quite some time.

After you get that down you can start adding in essential oils for smell or add in color with mica colorants, clay, or even cocoa powder if that’s you thing.

Clean up will be a breeze if you wait until the next day. All the oily residue that was left behind will have turned into soap as well, which makes for an easier time of it. (It makes my mom’s dishwasher smell fantastic! – C)

You’ve done It!

Or maybe you haven’t. It seems like a lot, but after a while it doesn’t take too much time and you can start playing around with additives like pumpkin puree, applesauce, even oatmeal. I swear there are more that aren’t food related, but I can’t think of them right now.

The possibilities are endless and if you don’t want to make it yourself there are crazy people like us who can make it for you. Check out our shop for all the fantastic ideas we’ve come up with. There are more soaps coming out every month so be sure to check back.

Want something that we don’t have in stock? Drop us a line and let us know. We might just be inspired enough to take it in a direction you didn’t want nor did you ask for. Either way, it is sure to be an awesome ride.