Soap Making

We are interested in soap making as a useful skill to manufacture something we currently take for granted and can buy very cheaply.

Since we have wood heating we have been building up a bit of a stockpile of wood ash which is currently stored in bins close to the house. I use a small amount to feed plants when applying pellet fertiliser (usually Dynamic Lifter).

So we have a lot of potash which can be used to make lye (sodium hydroxide). The technique is simple enough. A hopper is made to contain the ashes, and water is periodically poured and allowed to seep through to a collection container. This is kept out of the rain. The concentration of the lye can be increased by either running it through ashes again or boiling off water.

We had about 100 litres of wood ash. I sifted out the charcoal. I will think of what to do with the charcoal. It could be put back on the garden, used in a water filter, or burnt up in the fireplace.

Sifting Potash

Sifting Potash

Here is a picture of my Lye barrel. I practiced a bit of welding to make the small stand for the tub to sit on. A 6 inch hole was cut into the bottom of the tub and a bit of bird wire and shade cloth place over it to stop the ash from falling out.

After a few hours and about 30 litres of water gently poured onto the ash, brown liquid (potassium hydroxide, KOH) started to drip through. The following day we had about half a bucket of lye. It is difficult to know the concentration of the lye. And old method is the so called feather test. A bird feather is dipped into the liquid, if it starts to dissolve then the concentration is high enough for soap making. My feather did not appear to dissolve but went rather soggy.


Lye Barrel Full Of Potash

This type of Lye is apparently only suitable for making soft soaps. The recipes I have checked out so far are basically 2:1 ratio of tallow/oil to lye (or there abouts).

The first recipe I will try is:

  • One cup lye solution
  • Two cups oil

Since my Lye is already mixed into solution, I don’t need to add KOH crystals to water (which is an exothermic reaction). This is the the most dangerous part of the process and gloves and goggles are required.

There are heaps of articles on the Internet about soap making. Most describe accurate measurements for the ingredients. Since our Lye is of unknown concentration, it will be a bit of hit and miss.

Too much hydroxide and the soap will be caustic, causing skin burns.

Too little hydroxide and the soap will be greasy.

I have read that the pioneers would taste the soap (a little on the end of the tongue) and if it burned it was too caustic. I think I will use my soil pH test kit.



Hard Soaps

In order to make hard soaps, you need to use Sodium Hydroxide (NaOH). Typically you mix drain cleaner with water to make the Lye, a much more volatile reaction and very dangerous. So gloves and goggles are essential.


We don’t have a large supply of tallow. We slaughter a small number of chooks and may be enough to provide enough fat for some small batches of soap. We can make soap using a variety of oils (olive oil, vegetable oil). I think we will experiment making different types to learn about soap making. Producing a reasonable amount of tallow or vegetable oil ourselves is something we will need to investigate.

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