Thursday 27 September 2018

How to Make a Wood Ash Glaze (Revisited)

Wood Ash Glaze Tests

One of my most popular posts on this blog has been the one about how to make a wood ash glaze. It seems there's quite a few potters out there looking for information on this. So I thought I'd do an update in case anyone finds it useful or interesting!

I've completely run out of my first ash glaze - the one I made back in 2013. It was such a lovely glaze I used it on lots of pots. Since then I've moved house and now have a garden with mature trees which are always dropping branches. So I've got plenty of opportunities to gather wood ash from fires. I now have 2 bags of ash from the last 2 years of collecting.

Some of the trees in my garden

I don't separate the wood types when burning because it would take too long to gather enough ash. So the ash I've collected is a mixture of lots of different wood types including Ash, Chestnut, Apple, Oak, Damson and Hazel. We've also got a wood burning stove, so there's a mixture of 'shop bought' logs in there too.

Last time I posted about ash glazes I showed the glazing part. But this time I thought I'd do an update showing the ash sorting process. It's pretty simple really. Get your 'white' ash from a fire. It will have bits in it (leaves, twigs, charcoal etc). Then I use a normal kitchen-type sieve to separate the lumpy stuff from the white ash. 

Sorting Ash

At first I used a brush to help pass the ash through, but this was pushing bigger pieces past the mesh which I didn't want. So in the end I just tapped the sieve repeatedly on the side of the bucket and this was enough to shake it all through.

And that's it! No mystery. It does take a while to do least a couple of hours just to sort through two buckets. These photos were actually taken back in July on a very hot day. Sorting ash is a messy business so I sat in the garden in the shade under the trees wearing a mask and goggles and tried to avoid breathing in dust!

The first bucket of ash had hardly any debris because it came from outdoor firings (lots of leaves, twigs and cardboard burned). But the second bucket had lots of charcoal pieces left over from the wood burner - as you can see in the photo below. I've also kept the charcoal separately because it still had plenty of fuel left in it and I intended to use that for something else - which I will post about another time! And you might notice I also broke my sieve doing this bucket!

As you can see from the photo below, the end result is quite a uniform fine grey/white ash. And this is what I use as a dry ingredient in a wood ash recipe. I don't bother washing the ash because it seems to work fine without. (This might be because it's a mixture of wood types rather than just one.) I then use a 60 mesh to sieve the glaze. I usually don't use a finer mesh than this because I feel it takes out some of the 'material' that makes the glaze unique.

Wood Ash: ready to use

I've also made a couple of glaze recipe tests. The top tile test is the same recipe as the one from my original post. But it's a bit dry and matte this time around. So I think I'm going to try it again with a percentage of iron oxide - this might loosen it up a bit and make it more glossy. That's my guess anyway!

Wood Ash Glaze Test Tiles

But the bottom tile I really like. It's a recipe from Emmanuel Cooper's The Potter's Book of Glaze Recipes 181 page 102. A lovely pale green with a fleck. So I'm going to make a batch of this and try it out on some pots. I'm looking forward to seeing how they turn out!

Anyway, I hope you enjoyed that - and it might have been interesting or useful to someone! Thanks for reading!

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