All about Lye, and how to make it

Here is your ultimate guide to LYE – absolutely everything you need and want to know.  In this post, you will find the answers to the following questions:

  • What is lye and what is it used for?
  • Why do we need lye?
  • Is lye dangerous and what can go wrong?
  • Where can you buy lye?
  • How is lye made? (with a DIY recipe)
  • What are the alternatives to making lye? Can you make a shampoo bar without lye? (Spoiler: yes you can)

What is lye, and what is it used for?

You may have heard of lye already. We use it for making soap and cleaning products, including drain cleaner. You may have and heard all sorts of safety warnings about it too. 

Lye is a common name for Sodium Hydroxide, which has the chemical symbol NaOH.

It is a liquid we make by leaching ashes of potassium carbonate or potash. It’s an alkaline (basic) liquid with a pH is around 13. This is very alkaline, about as high as you can get.

Lye is a traditional soap that people used to make from lard and ashes.  Because it is very caustic, it is useful for cleaning.  We don’t use lard and ashes to make lye anymore.  Chemists normally make lye in a laboratory, however you can still make it yourself if you want to (not from lard!) – just scroll down for a couple of recipes. I’ve included an authentic lye-making recipe and an easier option.

Even though it might seem strange to use such a caustic substance to make something you put on your skin, you don’t need to worry.  Lye is often part of the process of making soap and shampoo bars, but the final product isn’t as caustic and is perfectly safe. We’ll explain this further soon.

Why do we need lye?

We need lye because in order to make soap and shampoo bars, we need a chemical reaction called “saponification”. Saponification describes the process when fat or oil is converted into soap by heat, in the presence of a liquid alkaline substance.

When we make soap bars and shampoo bars, lye is the “alkaline substance” we use, and the fat / oils are whatever we have in our shampoo bar recipes. People used to use animal fats, but now we (well, most of us) use oils such as coconut oil, shea butter, olive oil, cacao butter… there are a lot of oil options, outlined in our post on common ingredients in shampoo bars.

The chemical reaction of saponification creates what we call the “salts” of fatty acids, and the salts are the soap (the solid part) that is produced.

In the chemical reaction “saponofication”, the alkaline solution (the lye) almost completely disappears leaving behind just the soap, which we then use in regular soap bars or in shampoo bars. Conditioner bars usually don’t contain lye as they are designed to soften and moisturize rather than clean your hair. Shampoo bars do the cleaning part.

Is lye dangerous?  How to handle it:

You must handle pure lye carefully because it is caustic, or alkaline.  Caustic substances can burn the skin (think washing powder, dishwasher powder, drain cleaner etc) or corrode equipment. It has a pH of about 13, and that’s almost as alkaline as you can get (14 is the max).

But… lye doesn’t have to be dangerous, and a small amount along with other carefully chosen ingredients, can be a great way to make sure your shampoo bar cleans your hair properly.

This is what you need to do to use lye safely:

  • Wear protective clothing – goggles or glasses, gloves, long sleeves and shoes (just in case you drip or spill some).
  • Work in a very well-ventilated area. This means no enclosed spaces.  It’s a good idea to open your windows and turn on any ventilating fans etc.  Make sure you are breathing fresh air, not fumes.  Working outside is an option, and wherever you work with lye, make sure you keep it out of reach of animals and children.
  • Clean up as you go – if you spill lye, clean it up straight away, and if you get it on your clothes, change them.

So is lye dangerous?  Pure lye can be dangerous, but if you handle it correctly and use the right safety precautions you have nothing to worry about. But lye burns really hurt.  Follow the points above to make it as safe as possible.  And it goes without saying – keep out of reach of children.  If you do get it on your skin and you do get a caustic burn – apply first aid and see a doctor.

The good news is that the finished shampoo bar won’t actually contain anything dangerous – it’s just part of the soap or shampoo bar making process that we described above.

You’ll most likely have everything you need to handle lye safely at home already, but if not, here are some options from Amazon. Supermarkets, hardware stores also sell these items.

Where to buy Lye

If you’re wondering where to buy lye, the easiest place by far is Amazon. You can also buy it anywhere that sells soap-making supplies.  It’s often labelled or described as “lye for soap making”.  It is pre-made for you, comes in a safe container, and is already at the required pH for successful shampoo bar making or soap making. 

Buying pre made lye is a safer, simpler option than making it. You don’t need to mess about with collecting ashes and rainwater, and it’s a lot less messy. If you do want to try making lye yourself, I’ve included a few methods, just scroll down.

Here are some pre-made lye options to suit most budgets:

Some people ask if lye is vegan.  As it only contains ashes and water, yes – lye is vegan. As long as you use vegan oils to make your shampoo bar (coconut oil, shea butter etc) rather than animal fats, your finished project will also be vegan. I don’t think anyone would use animal fats to make soap or shampoo bars these days. Almost all shampoo bar recipes are vegan.

How is lye made?

Originally people made lye with wood ashes and water. These days we make it in a lab.  This makes our life much easier – you can just buy pre-made lye solution to use in your shampoo bar recipes.  But if you want to make pure lye at home, you can.  It is not complicated.   You just need two ingredients, and you can make it at home in your garden or kitchen. We’ll explain what you need and how to make it (two methods, one authentic and a cheats / easy version).

What you need to make Lye at home:


  • Ashes from a hardwood fire. The ashes should look really white.  A hardwood fire is a fire from wood like beech, hickory or ash wood.  These are known as hardwoods, and contain potassium (important for lye making).  Don’t use soft woods as there won’t be enough potassium and they are too resinous for shampoo bar making.  Pine, fir, spruce or other softwoods won’t work.
  • Water – The water you use should be soft water.  This is because it contains less minerals and will make a shampoo bar that lathers well.  We all like bubbly shampoo!  If your tap water is hard water, try collecting rain.  Read more here about soft vs hard water.

We are including two methods you can use to make lye at your home or in your kitchen. The same two ingredients are in both methods – hardwood ash and water – but each method has a very different process.

Method 1 is the normal, probably more authentic method. You’ll need a bit of extra equipment, but as long as you can find the right things, the process is simple.

Method 2 is a bit of an easier method and doesn’t require as much equipment.

Method 1 (normal method):

Equipment: Wooden barrel, on a stand or raised surface, drill, bucket, stones and straw, pH testing strips.

If you don’t have a wooden barrel (let’s be honest, who does) then you could try to source a second-hand, old one online. You can sometimes find them at hardware stores, gardening stores or wineries, but an old one will do. Any stones will do, and straw is easy to find as it is sold in most pet stores.


  1. Drill holes near the bottom of the barrel.  Put stones and straw in the bottom , and put the ash on the top (as much as you have – the more ash, the better).
  2. Set the barrel up so that water will drain out of the bottom and collect in a bucket.  You will need to put the barrel on a higher surface or stand, or pile of wood. Add water (soft / rain water) to the barrel and fill to the top.
  3. Let the water drain through the ashes and into the bucket. This can take a long time, you can leave it for hours, or overnight.
  4. Tip the water back into the top of the barrel and let it drain through the ashes again.
  5. Collect a small amount of water, and test the pH using the testing strips. 

When the pH is 13, you can use it to make shampoo bars or homemade soap. If the lye liquid is not alkaline enough, tip it back into the barrel and let it filter through the ash again.

Method 2 (the easy method):

Equipment: Pot or pan, large spoon or ladle, pH testing strips.

Use old or second hand equipment, that you can keep just for shampoo bar making.


The easy way to make lye is to boil the ashes in water on the stovetop then turn off the heat. After the ash has settled, scoop the liquid off the top.  Remember to wear gloves, goggles and boots and try not to spill any. Don’t breath in the steam when the water is boiling, and make sure you open the kitchen windows and turn on the ventilating fan if you have one.

Test the pH using the testing strips or a digital pH tester.  When the pH is 13, you can use it to make shampoo bars or homemade soap. If it’s not alkaline enough, put the liquid back in to the pot and repeat the process.

You can buy pH testing strips anywhere that sells swimming pool supplies.  You can buy them at your local hardware store, or order them online. Here are some options:

What are the alternatives to lye?

In this section, we explain what you can use if you don’t want to handle lye. Although using lye is relatively simple, some people don’t want the bother of handling it at all. Or, they may want to involve children in making shampoo bars, and therefore need to make the process as safe as possible. No problem – there are other options!

There are couple of ways to make shampoo bars without lye. You can use a pre-made soap base, where the lye part has already been done for you, or you can make a shampoo bar using a completely lye-free recipe. We’ve discussed both below, so that you can choose the option that suits your needs.

1. Use a pre-made melt and pour soap base 

Technically this still includes lye, as it is part of the process of making the base.   But when you use a pre-made melt and pour base, you don’t need to make or handle any lye yourself.  You don’t need to avoid lye, but if you don’t need to handle it yourself, all the better.

A melt and pour base comes in bars which you, as suggested by the name, just melt, add your other desired ingredients, then pour into your own soap molds.  There are lots of different kinds of melt and pour base, so you can choose one to suit what you are looking for. If you, like us, like to avoid palm oil in products, make sure you check the ingredients in the base you are using. Most are palm oil free, but it’s best to check.

You will have the cleansing benefits of lye without the hassle of handling a caustic substance.  Lots of recipes call for a soap base.  Here are a couple of excellent melt and pour options:

2. A completely lye-free shampoo bar recipe

Although hard to find recipes online – you can make a shampoo bar that is completely lye-free! 

Lye is alkaline, which means it has a high pH. Sometimes our skin just doesn’t like it.  Read more about why here.

You might have to be a bit more organised to make this recipe as you need more ingredients, but the result is worth it.  If you click on the image to the right or on the link below you will find a recipe for a completely lye-free soap on this website, with detailed descriptions of the ingredients and process to follow.

Click here for lye-free shampoo bar recipe



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