Last year I decided to resume my passion for modeling clay and in particular stoneware and porcelain clay.
I decided to specialize in single firing (I had a book taken in Scotland several years earlier).
At the moment I'm cooking at 1240°C, non-stop. The cooking lasts 3 hours between 0 and 200°C and then travels at a speed of about 100°C per hour (if I remember correctly: the oven is not mine).
I'm doing glazes experiment using wood ash. This idea came from the fact that we use the fireplace and in particular the pellet stove for the winter.
Wood ash from the pellet stove is probably not ideal: because some of the finer particles are lost and the sieve work is longer and give a coarser material. But I have a lot of ash from this stove and it's a shame not to use it, if possible.
I had some book from Scotland about ash glazes and cone 6 glazes and I'm starting from them.
To make my life easier, I use wood ash washed several times but I do not dry it: I let it settle and remove the surface water leaving only about 1 cm of water.
At the beginning I used a volumetric system in the first 2 recipes (photos).
Recipe 1:
- 1 jar of dense slip of 1250°C spotted stoneware clay
- 1 jar of thick potassium feldspar slip
- 2 jars of dense wood ash slip
Recipe 2:
- 1 jar of dense slip of porcelain clay
- 1 jar of thick potassium feldspar slip
- 2 jars of dense wood ash slip.
Than I made 2 little experiment with a little of cobalt and copper oxide.
I calculated that those slips contain approximately 50% water and 50% clay or feldspar. Instead, I estimate a quantity of about 300 grams of dry ash in a liter of ash slip. The calculation is very approximate but future experiment I am conducting will be based on this hypothesis.
First experiment with wood ash glazes
by Luca
Feb 20, 2021
Last year I decided to resume my passion for modeling clay and in particular stoneware and porcelain clay.
I decided to specialize in single firing (I had a book taken in Scotland several years earlier).
At the moment I'm cooking at 1240°C, non-stop. The cooking lasts 3 hours between 0 and 200°C and then travels at a speed of about 100°C per hour (if I remember correctly: the oven is not mine).
I'm doing glazes experiment using wood ash. This idea came from the fact that we use the fireplace and in particular the pellet stove for the winter.
Wood ash from the pellet stove is probably not ideal: because some of the finer particles are lost and the sieve work is longer and give a coarser material. But I have a lot of ash from this stove and it's a shame not to use it, if possible.
I had some book from Scotland about ash glazes and cone 6 glazes and I'm starting from them.
To make my life easier, I use wood ash washed several times but I do not dry it: I let it settle and remove the surface water leaving only about 1 cm of water.
At the beginning I used a volumetric system in the first 2 recipes (photos).
Recipe 1:
- 1 jar of dense slip of 1250°C spotted stoneware clay
- 1 jar of thick potassium feldspar slip
- 2 jars of dense wood ash slip
Recipe 2:
- 1 jar of dense slip of porcelain clay
- 1 jar of thick potassium feldspar slip
- 2 jars of dense wood ash slip.
Than I made 2 little experiment with a little of cobalt and copper oxide.
I calculated that those slips contain approximately 50% water and 50% clay or feldspar. Instead, I estimate a quantity of about 300 grams of dry ash in a liter of ash slip. The calculation is very approximate but future experiment I am conducting will be based on this hypothesis.