Usage of Colemanite in Transparent Wall Tile Glazes

Abstract

Boric oxide has an important place in glaze technology and is the second most important network-former after silica. Lower thermal expansion coecient; higherchemical and mechanical durability; good glaze appearance are some of the benets of boric oxide. In wall tile production; generally transparent frits with 17% boric oxide are used to obtain glossy transparent glaze. It can be said that boric acid is the fourth expensive raw material in frit production after zirconium, zinc oxide and potassium carbonate due to its high cost limits its usage in frit production. The aim of this study is to investigate colemanite (CaB3O4(OH)3•H2O) mineral usage in transparent frit production instead of using boric acid. To achieve this aim, four dierent frit mixtures Std, K.1, K.2 and K.3 with 0 wt.%, 3 wt.%, 6.5 wt.% and 11.5 wt.% colemanite content were prepared respectively. For comparison of the thermal behavior of frits, hot stage microscope was used. It was observed that, all of the samples prepared with colemanite have lower sintering and softening temperatures than the standard recipe because of its high earth alkaline oxide content. The obtained glazes were characterized by X-ray diraction, dilatometer, Harcourt and Autoclave tests.