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DIY Soap Making Natural From Scratch, Part 2

  • DIY

How to Make Lye out of Ashes



Before discussing how to make lye, it is important to note that lye is very dangerous and extreme caution should be used when making or handling lye – whether commercial or homemade. Lye should never come in contact with aluminum, as it will react with the metal. Lye can cause chemical burns if it comes into contact with skin, and blindness if it gets in your eyes.

There are numerous ways to make lye from wood ash. Some instructions suggest that you mix ash with hot water and let it set before filtering out the ash. Others will tell you to drill holes in the bottom of a barrel, cover with straw, and then fill with ash. Water is poured over the ash and lye is leached as the water filters through the barrel and is collected by a pan underneath the barrel. This works, but your lye is likely to be discolored by the straw. When lye reacts with lignin in the straw, the bonds are broken down and the fibers are left behind. After enough leaching, the remaining straw fibers work as an effective filter, but will no longer discolor the lye.

Regardless of the method used, the more times you run the lye solution through a bed of ashes, the stronger the lye will become. Instead of successive leaching, you can also boil the lye to strengthen it. The water will evaporate but the lye will not, so the solution will contain a higher percentage of lye.

One of the difficulties when making lye is determining proper strength. One traditional method of determining strength is to see if a chicken feather will start to dissolve when placed in the lye water. A more accurate measure is to float an egg (still in the shell) in the lye solution. If the lye is of proper strength, the egg will float but only a quarter sized circle of the egg will be raised out of the water. If it floats too high, the lye is too strong. If it doesn’t float high enough, then the lye is too weak. Discard the egg after testing; it is not safe to eat. Source

You need:

  • Ashes from wood (3/4 of your bucket)
  • Rain- or distilled water (fill your bucket up to the “top”)


  1. Make wood ashes. Your wood should be burned in a very hot fire to make very white ashes so the wood has to burned hot and complete. You can burn dried palm branches, dried out banana peels, cocoa pods, kapok tree wood, oak wood and other wood trees – no pine. Hardwood trees will result in better quality lye than if you use ash from soft woods or conifers.
  2. When the fire is out and cold, gather only the finest of ash. Avoid any wood chips.
  3. Place 3/4 of ashes in a bucket or barrel. Do not use metal. Use wood, glass, or plastic containers.
  4. Slowly, fill up the rest of your bucket with (boiled) rain water or a ”soft water” (distilled), because it does not have metallic or acidic chemicals in it which will interfere with the soap making chemistry. Do not add the water too fast, don’t allow the ashes swim/float around.
  5. Let this sit over night or even longer.
  6. Continue with separating the ash from the brown lye water, by using mesh to strain it very finely.
  7. Do the egg (fresh) test, if it sinks you have a weak lye water which means you need more ash to raise its strength. Do this by continuing the steps above by using more ash. Add the lye water to the new mix and again let it set over night. If the egg or a potato floats, then your lye water is ready. Be sure the egg doesn’t rise too high (less than half submerged) as this is an indication that the lye is to strong. Add soft water until the egg doesn’t float that high.

Source 1, Source 2

Alternate Instructions for Making Lye from “Rogueturtle”

  1. Fill your lye-making barrel or drum with ashes to within 10cm of the top.
  2. Boil 1/2 bucket of soft water (5 liters) and pour over the ashes.
  3. Slowly add more cold soft water until liquid drips out of the barrel.
  4. Close the tap or block the drain hole.
  5. Add more ashes to the barrel, adding water as needed to fill it up. Don’t let the ashes “swim” in the water.

A nice shown video about making lye. With the difference that ash and water are heated up together.

Preparing fats from animals
Cut away the fat without any of the meat still attached. 100% pure fat! This cleaning of fats is called rendering. Fat obtained from cattle is called tallow while fat obtained from pigs is called lard. Then, place the fat in a cast iron frying pan or a big pot.

Cook it on really low heat! Don’t burn the fat and also don’t overcook it so it becomes rancid. Let it fully render until it turns to liquid. Stir it from time to time. This may take about to 3-4 hours. When it’s done, there are these hard pieces left which are called crackles. They are quite hard so you can tell all the soft parts have now become liquid. Strain the liquid through a cheese cloth for purifying it and it is best to do so directly in to a glass container. If the fat cools down, it will get hard again but it can be melted up if needed. You can store the fat in glass containers for quite a few years in a dark and fresh room. You can also use the fat as a candle, with a wick in the middle. Source 1, Source 2

For more details of rendering and melting fat, watch this video.

Making Soap – Final

Too much lye will cause the soap to burn the skin! The lye mixture is added to heated fat. You can also use a lye calculator if you use different fats and Sodium Hydroxide (NaOH) or Potassium Hydroxide (KOH). Source

How to video from “Mike Reed Outdoors”
4 gallons (15L) wood ashes (in a 5 gallon (19L) bucket)
2 gallons (7.6L) of hot water
1 pound (500g) of lard
3.04 oz (90ml) lye
6.67 oz (200ml) water

Saponification Calculator

To find the right measurement, depending on which fats or oils you use, the value of Potassium or Sodium has to be valued. SAP for Saponification and the value in milligrams of Potassium or Sodium means X ml Potassium or Sodium required to saponify 1g of fat. Source

For example with Coconut Oil
1g Coconut Oil needs 6 mg Sodium hydroxide (NaOH)
1g Coconut Oil needs 8 mg Potassium hydroxide (KOH)
You can find a whole list (US measurement) here
Or use an online calculator

Please let me know if you have experience with making soap out of lye and which measurements worked for your soap!

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