Abstract: A composite glass ceramic material which comprises silicon nitride (Si.sub.3 N.sub.4) whiskers in a glass ceramic material comprising nitrogen doped cordierite, which composite material has greatly increased strength at elevated temperatures, good microwave transparency, and good thermal shock resistance.The invention further comprises a method for manufacturing the composite material by blending ground nitrogen doped cordierite glass with between about 5 and about 50 percent Si.sub.3 N.sub.4 whiskers by weight of glass. The blend is then formed into a desired shape and is sintered at an elevated temperature of from about 1000.degree. to 1400.degree. C.The invention also includes the novel nitrogen doped cordierite glass and glass ceramic made therefrom.

Abstract: This invention is directed to the production of glazes exhibiting an earthenware appearance which are particularly suitable for decorating ceramic dinnerware. The glaze composition consists essentially of about 4-8% by weight SnO.sub.2 and 4-8% by weight TiO.sub.2, the total SnO.sub.2 +TiO.sub.2 being about 10-14%, and about 0.025-0.04% by weight MnO.sub.2 incorporated into a base frit consisting essentially, as analyzed in weight percent on the oxide basis, of about______________________________________ SiO.sub.2 37-49 Al.sub.2 O.sub.3 4-7 B.sub.2 O.sub.3 6.5-11 ZrO.sub.2 0-1.75 Na.sub.2 O 1.75-3.5 K.sub.2 O 0.75-2.5 PbO 21-32 CdO 0-0.75 CaO 1-9 TiO.sub.2 0-0.35 F 0-0.6 ______________________________________The fired glaze contains crystallites of rutile and cassiterite.

Abstract: Spontaneous sodium fluoride opal glassware is treated to improve surface durability against aqueous attack by controlled sodium depletion and subsequent heat consolidation of the glass surface. The method comprises extracting surface sodium ions using water or dilute aqueous acidic solutions and subsequently consolidating by heat the surface to produce a glossy surface without any migration of sodium ions.