Published Dec 19, 2018
Mark Issenberg shares some ceramic glaze recipes that utilize fireplace wood ash to create an ash glaze surface. Plus he shares his tips for using a spray gun to apply the glazes. Judging from the brutal winter, fireplace ash should be easy to come by. And, hopefully, you can clean out your fireplaces and not have to fire them up again until next winter! - Jennifer Poellot Harnetty, editor.
I started using ash glazes because I liked the idea of utilizing a material that many would consider waste: wood ash from a fireplace. While living in Miami after Hurricane Andrew in 1992, there was an abundance of wood for fires on cool nights, so I had a source of ash. I decided to make ash glazes using 50 parts Redart and 50 parts ash.
Through my experimentation, I learned to use sprayers for applying an ash glaze. To begin, prepare ashes by running them through a flour sifter to remove unburned wood, charcoal and big chunks of debris, then run the dry ash through a 40-mesh screen. I usually process a 5-gallon bucket of ash at one time.
Caution: Wood ash is caustic, so work in a well-ventilated area with a respirator, and wear safety goggles and chemical resistant gloves.
The next step is to weigh equal amounts of ash and Redart clay. I only mix up what I'll use in one firing (1000 grams of each) since the ash glaze does not store well. After mixing with water, run the glaze through a 40-mesh screen then through an 80-mesh screen to get it to the right consistency for spraying. Use a thinner glaze than you would for dipping or pouring.
Work with the spray gun about 5-12 inches from the surface and use steady even strokes to avoid getting excess glaze in any one spot where it can drip. Use a sponge to clean the footring. I don't use wax on bowls because the glaze builds up and runs off the wax, but I do wax flat bottoms. I then flip the bowl and spray the inside using a couple of different glazes. When fired, ash glazes run but some of the other glazes don't run at all. Testing determines how certain combinations will behave.