|Monthly Tech-Tip |
It makes sense to maximize the percentage of wood ash. This glaze was the product of preparing a large ash batch and a project to develop a glaze specifically from it. This one contains a little iron to brown it. Ash generally contains low percentages of Al2O3, a critical oxide needed for stable glass development. I added kaolin (about 20%), it suspends the slurry and supplies Al2O3. Ashes contain lots of fluxing oxides, but they still may need a little help to melt a glaze at cone 6, so I added feldspar (it also supplies more needed Al2O3). For better melting add some borax frit (like Ferro frit 3195). If crazing occurs use frit 3249 instead. Use whatever feldspar and kaolin you have.
Wood Ash Glaze
Common washed wood ash has a chemistry akin to a ceramic glaze, so it can comprise significant percentages in a recipe. Plus it can produce unique visual effects.