| abstract |
A mixt. is made contg. by wt. 70-99.5% milled stone materials (I), plus 0.5-30% of one or more meltable substances (II) which are insol. in water, and/or substances (III) which increase the covering power of the glaze. Materials (I) contain 40-85% SiO2, 5-20% Al2O3, and have a m.pt. below 1450 deg.C, and are volcanic rocks. Materials (II, III) may include 5% max. pigments. Materials (I) are pref. waste obtd. by crushing stones and/or boring tunnels, or gangue obtd. from ore- or mineral- mines, whereas materials (II) are pref. calcium borate, CaF2, alpha- calcium silicate, and/or scrap glass. The mixt. is pref. baked onto ceramic objects at 1000-1250 deg.C, or sprayed at much higher temps., e.g. via a plasma, onto concrete. The mixts. obtd. are crude glazes, which do not need initial fritting, and are therefore inexpensive, esp. when they are made from waste prods. |