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You are here: Home arrow Articles arrow Make your own arrow Making soap from woodash lye


Making soap from woodash lye

Written by sally_in_wales

Please note, this article is offered primarily as a novelty. Whilst you certainly can make soap successfully from woodash lye, it is a slightly hit and miss process and you may find it faster and more reliable to make soap using a commercially available lye carefully weighed to convert exactly the right amount of fats into high quality soap. Please also note that any form of soapmaking involves working with highly caustic substances, and all sensible precautions should be taken. In the photos I am not wearing gloves and goggles- I really should be.

Stage one: Collect your ash.

Ashes for soapmaking have historically come from a wide range of sources including seaweed and bracken, but for our purposes the ashes you want come from burnt hardwoods. Softwoods don't give nearly as good a result. You need far more than you might think, so save up your ashes over the winter, preferably from fires that haven't involved firelighters, masses of paper or other rubbish, and keep them somewhere dry and airtight until you need them. Mine were from a mix of primarily beech, oak, ash and a bit of other typical British woodland trees, and the cold ashes went into a plastic lidded dustbin where they sat for a year waiting for me to get round to this.

Stage two: Set up your lye barrel.

Traditionally, one uses an old wooden barrel or lye hopper for this, even hollow treetrunks in some areas, but in this day and age the trusty plastic dustbin is probably the most accessible container. Drill a hole near the bottom and fit a bung so you can draw off the lye later.

In the bottom, put a filter made from a couple of inch depth of twigs, and the same again of straw or hay. This helps ensure the lye comes off moderately clear.

Stand the lye barrel up high enough to get a container underneath (plastic, glass or stainless steel is usually best, be aware that lye will eat through aluminium), make sure it is stable, and fill it up with those ashes.

Add water. It will take far more water than you think, I had to come back a couple of times and add more as it soaked into the ashes.

Tasty looking isn't it! Anyone for cindersoup? Leave it all overnight. In my case, my bung isn't a perfect fit so it was already dripping nicely into my container when I got up, but if yours is watertight, draw the bung and let the lye run out into your container.

At this point learn from my mistakes! I came down to half a bucket of what looked very much like cold coffee, and whilst I was expecting it to be alkaline, I forgot just how strong it was likely to be at first run, so I put a drop of the slick, soapy feeling liquid on my tongue to test the relative alkalinity. Bad move, it was painfully strong, and I was lucky not to do myself a mischief. Whilst cautiously taste testing lye and soap is a time honoured way of estimating strength, its not necessarily the most sensible, and using ph papers wouldn't be a bad move instead.

I decanted this off into a storage jar and put the bucket back to catch the next batch as it dripped out.

Stage three: check your lye strength

A lot of the old soapmaking texts say lye is strong enough for soap when you can float a fresh egg in it with a good portion showing above the surface. Mine from the first run of lye floats an egg with a small amount showing above the surface. (Its got to be a fresh egg, because an old, stale egg will float anyway.)

From here, I could boil down the lye to concentrate it, but as its not that far off strong enough I decided to carry on and adjust the soap as I went with more oil or lye as needed.

Stage four: make your soap!

I'm using olive oil for my batch, I want a soft soap that can be used for a variety of household tasks. Other fats work fine, but your batch may look a bit different to mine.

In this picture I have added a pint of oil (transparent and faintly greenish gold in colour) to a pint of lye (looked like black coffee)and whisked it together. I immediately got this milky looking slightly emulsified concoction, and yes, those are a few soap bubbles on top! This is with cold ingredients and about 2 minutes whisking.

I'm expecting to need to heat this up for the reaction to work properly, and I'll almost certainly need to add more lye or oil later on. For now though, it can have a few hours sitting quietly and being whisked every time I walk past it until we put the stove on later.

2 hours later it visually looks about the same except there are more bubbles when its whisked. I put it on the edge of the stove at this point to warm it up gently.

After 2 hours on the edge of the stove barely simmering away, we have trace! This is the point at which you can see the trail left by the spoon in the soap for a few seconds, and its always really encouraging. Its still a long way from done and the alkalinity is very high still, but I'll leave it settle overnight now and will test and adjust in the morning. That dark colouration has just about gone as well, doesn't look much different to soap made with granulated lye at this point.

The next morning, we have a thick creamy mass in the pan similar in texture and appearance to thick yogurt. Its still highly alkaline by the pH papers (although interestingly, soap does odd things to pH papers and they aren't always fully accurate on soap for some quite complicated reasons, soap is often a higher pH than the papers indicate), but it is neutral on the tongue and there is a lot of oil left when its rubbed between the fingers. So, another pint of lye is going in, and it will get warmed up at lunchtime and we shall see what happens.

It might seem odd to be adding more lye when it is still showing as more alkaline than finished soap should be, but whatever is still in there is no longer doing its thing to create soap, so topping it up will hopefully bring the conditions back up to a point where the reaction starts up again. Soap is pretty much always alkaline even when finished unless you add things to get it close to neutral, but there is a point where its definately alkaline but not enough to create more soap from any fat that hasn't been converted yet. I won't pretend to completely understand the chemistry at this precise point in the conversion from fat and lye to soap, I'm just doing it according to the old methods and using touch and taste to indicate what needs doing next- without the indicator paper, the taste and touch tests would have suggested it was more or less 'neutral' in the broadest sense of the word even though the actual ph is still quite high.

After a couple of hours more very gentle cooking, during which time we have had the full repertoire of 'boiling goo' 'imminent volcano' 'bloop bloop gloop' and other interesting visual effects, the pan looks like this. (Best description I can offer is to say it as the colour and texture of those strange butterscotch puddings that come in packets and which you add milk to, the sort of thing you may have had for pudding when you were about 5 or so). It also now comes away from the side of the pan when you tip it.

With normal soft soap, I would expect it to be turning darkly transparent about now, but possibly due to impurities in the lye, its staying opaque.

A sample mixed in water now does this- bubbles! It now feels and acts like any other soft soap, the ph of the bubble mixture is down to about 9, thats only a little bit higher than a plain handmade soap that hasnt been superfatted, and it has stopped 'biting' when tasted. This may also come down a little bit with time as soap continues to finish for several days after making.

The soap now gets to cool down very slowly in a warm place, but essentially that worked. Twice the volume of lye in which you can float an egg to oil, and a lot of slow steady cooking = soap.

The finished product:

This is the soap potted up the next morning, a good pint or so of finished soft soap.

and this one is the empty pot getting washed up, those bubbles are all from the soft soap residue in the pan. They feel lovely and creamy on the skin and have a pH (by indicator papers, so may be off slightly) of about 8. This batch of soap will probably mostly get used for scrubbing down woodwork and washing greasy fibre.