While the ash of most plants is very high in fluxing oxides like CaO and MgO, some plants take up much more free silica from the soil and have ash that can be high in silica particles (e.g. rice husk ash). Prolonged breathing of such exceptionally fine particled ash over time can cause silicosis.
When added to glaze suspension the ash will generally create a caustic and corrosive base that can cause skin reactions in some people (even severe reactions), thus is best to wear rubber gloves when working with ash glazes.
|Materials||Rice Straw Ash|
|Materials||Rice Husk Ash|
Silicosis and Screening
SILICOSIS and SCREENING by Edouard Bastarache
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.