Hydrated aluminas are fine granular white powders that have good flow properties. As with any form of alumina, this material has a very high melting temperature. Notwithstanding this, it disassociates enough in many glaze types to be useful as a source of Al2O3 to the melt (however the finer the particle size the better). The hydrated version of alumina stays in suspension better in glaze slurries and has better adhesive qualities. Also using hydrated alumina in glazes and glass can promote the fining operation of coalescing and removing finely dispersed gas bubbles. Small additions of fine alumina hydrate added to a glaze can also enhance the color of Cr-Al pinks. Larger additions of fine material can impart matteness if the glaze is able to take it into solution (sourcing alumina from kaolin, feldspar and frits may be more practical). Alumina hydrate promotes opacity in enamels and glazes by generating gas bubbles in the glaze melt.
Chemical Formula: Al2O3 3H2O
Synonyms: Hydrated Alumina, Alumina Hydroxide