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What is Lye?

Lye is a strong alkali that is used in soap making, among other things. It is also known as caustic soda or sodium hydroxide (or historically potassium hydroxide).

Lye Ingredients

The ingredients for making lye are wood ash and water. Preferably rain water, as it is soft, although tap water will work just as well. The ash should come from hardwoods as soft woods are too resinous to mix with fat. Ash and Beech give good results.

The Traditional Method of Making Lye uses Wooden Box or Barrel

Take an old wine barrel or stout open wood box and make sure that it is clean. Elevate it so that you can then place an iron bowl, bucket or similar underneath the leaching hole at the bottom of your barrel/box to collect the lye water when it is ready to emerge. Place a bung in any existing opening in the wine barrel, and drill a smaller hole into the barrel/box that is only 1/8th inch wide. What you are aiming for is a hole wide enough for the water to drip through but small enough for the ashes not to fall out. Keep this hole closed up with a small bung until later.

Now pack the bottom of the barrel with clean river stones. If using a box a layer of charcoal will do. This works as a filtration system. After the filter place a generous layer of straw on top. Your straw should take up at least half way up the barrel/box.

Shovel in your ashes until the barrel/box is as full as you want it. You can add a thin layer of straw to keep the ash in. After that, pour over some hot rain water in small amounts so that the whole contents are wet and soaking but not flooding. Using hot water is important as the hot water will draw out more potash from the wood ash than cold water, making your lye stronger.

Traditionally, a little lime was mixed with the ashes to 2 – 5% which then guaranteed that you would have good lye for soap making.

On day 2 you can add more ash and water after allowing the ash from the previous day to settle.

  • If your ashes start floating to the top then you know that you have added too much water.
  • Make sure that what you are placing in the bucket is the fine, white ash, as opposed to any charcoal bits.  These you don’t need.
  • To make your lye potash more like caustic soda you can sprinkle a little quick lime onto your ashes before pouring on the hot water. (Not easy to get in small quantities these days, and treat with caution as it needs to be handled with extreme care.)

On day 3, make sure your receptacle is ready under the opening on the barrel/box, remove the bung and wait for the lye water to slowly trickle out. Don’t expect to have a bucketful. You will only be getting a small amount as this should give you the right strength needed to make good natural soap.

At this stage you need to get it to an even strength to use for your soap making. Boil this liquid again until you are able to do the “float test” and get it to work. See instructions below.

This is the traditional way to make lye. Winchester’s have a suitable box which you can use to demonstrate the process. It needs to be set up in a tilted position and draining into a suitable receptacle.

If you make lye this way, take care at this stage as the lye is caustic and if it splashes onto your skin and into your eyes it will burn. You will need to wear gloves (and safety glasses if out of the public eye) at this point.

Once you have enough lye water boil it carefully and then pour it back into the bucket/box for a second go. This will strengthen the lye.

How to Test the Strength of your Lye

To make lye and be successful at soap making your lye has to be at the right strength. Now there are 2 ways in which this can be done, both of which indirectly involve chickens.

Test 1

This is a simple test. Take a chicken feather and place it in the lye. If the feather dissolves, the lye is strong enough and you can use it for your soap. If not, you will have to re-boil the lye water when it emerges and repeat the process until your chicken feathers dissolve.

Test 2

This test involves using a fresh, whole egg or a potato works just as well. Take the egg or potato of similar size and place it in the cold lye water.  If it sinks, your lye is not strong enough and you will have to repeat the process until it does.

If the potato floats with just a little of the lye water above it; about an inch showing above the water, or the head of the egg sinks to just half-way down, then the strength is just right.  If the potato or egg floats too high, almost on top of the lye water, then the strength is too strong.  You can compensate by adding a little bit of fresh water to the lye water and try again.

Now to Make Natural Soap with your Lye

Here is an original pioneer soap recipe using your homemade lye water.


2 pounds fat or lard
1 gallon homemade lye water
2 tablespoons white vinegar
1/2 cup hot water


Place the fat and lye water in a large pot suitable for soap making (not aluminium).  Add the vinegar mixed in with the water.  Keep on a rolling boil until thick and slimy.  This can take several hours.

If at this stage you want to use it as soft soap it is ready after straining through several layers of cheesecloth before placing in storage containers.  One cup of homemade liquid soap per load is all that is needed.

If you want hard soap you will need to add 1 teaspoon of salt dissolved in a little water to the mixture at this stage and boil for longer.  Skim the foam off the top and place the liquid into moulds and allow to set.  There are wooden soap moulds in the Winchester’s soap making kit.  These should be lined with cloth to enable you to extract the soap once it has hardened.

Another Pioneer Soap Recipe using Homemade Lye

Fill a pot 2/3rds full of homemade lye.  Place on the stove over a medium heat and ladle in spoonfuls of melted lard and stir until your mixture is creamy.  Now add pinches of salt to the mixture and stir until a ring of soapy mixture is left behind and very evident on the stirring spoon.

Remove from the heat and allow the soap to harden.  After it has hardened you will need to drain the remaining lye water off the soap.  You can make soft soap in the same manner if you don’t add the salt at the end of the process.

Basic Lard Soap Recipe


16 oz (454 g) lard
7 fluid oz/ one third of a pint of lye.


Prepare the soap moulds.  Melt the lard in a saucepan until it has all melted entirely.  When it has cooled to around about 50ºC (125ºF) slowly pour in the warm lye in a thin stream with constant, slow stirring.  The mixture should start to thicken.  Trickle some of the mixture off the back of a spoon to see if it will leave a trace.  Wear gloves or gauntlets when in Living History.

Add any optional colouring and essential oils and stir.  Pour into the moulds.  Cover and leave for several hours to set.  Then cut the soap in the moulds with a metal knife to the size of bars you want to finish.  Once you have cut into bars, leave the soap in the moulds for at least a week before removing it.  Place in a dry place for a month to harden further.

To Make Lye using Caustic Soda

Use distilled water if possible, or plain tap water.  Place the water in a metal saucepan (there is one in Winchester’s kit).  Wearing rubber gloves (and eye protection if possible) add caustic soda, stirring constantly.  It will react strongly and get hot.  Cover with a cloth and leave to cool to about 50ºC (125ºF).

It is then ready to add to the melted fat/lard.  This should be done slowly in a thin stream, stirring constantly.