Abstract: This invention is directed to the production of glass-ceramic articles exhibiting great toughness, a modulus of rupture of at least 20,000 psi, and, in the form of bars having dimensions 5".times.0.5".times.0.1", sagging during the crystallization heat treatment of no more than 0.2" over a 4" span, and wherein potassium fluorrichterite constitutes the predominant crystal phase but wherein cristobalite is also present in an amount of at least 10% by volume. The inventive articles having an overall composition consisting essentially, in weight percent on the oxide basis, of:______________________________________ SiO.sub.2 65-69 Na.sub.2 O 1.5-3.3 Al.sub.2 O.sub.3 0.75-3.5 K.sub.2 O 4.2-6.0 MgO 13.5-17.5 BaO 0-2.5 CaO 3-4.8 P.sub.2 O.sub.5 `0-2.5 Li.sub.2 O 0.5-2.0 F 3.3-5.

Abstract: The present invention is concerned with the preparation of glazes which are especially suitable for application to glass-ceramic articles containing potassium fluorrichterite as substantially the sole crystal phase. The glazes consist essentially, expressed in terms of weight percent on the oxide basis, ofSiO.sub.2 :46-50Al.sub.2 O.sub.3 :5-8ZrO.sub.2 :0.3-1Li.sub.2 O:1-2Na.sub.2 O:2-3.5K.sub.2 O:1-2CaO:1-4ZnO:2-6SrO:2-6B.sub.2 O.sub.3 :9-11PbO:20-25.

Abstract: There is disclosed a highly crystalline glass-ceramic article exhibiting superior toughness against fracture propagation, a modulus of rupture in excess of 20,000 psi, a predominant crystal phase of potassium fluorrichterite, and having an overall composition consisting essentially ofSiO.sub.2 : 50-70CaO: 4-15MgO: 8-25F: 3-8Na.sub.2 O: 2-9K.sub.2 O: 2-12Li.sub.2 O: 0-3Al.sub.2 O.sub.3 : 0-7Canasite may be a secondary phase, but a crystal phase composed essentially of potassium fluorrichterite is preferred for dinnerware.

Abstract: The instant invention is concerned with the production of spontaneous opal glasses exhibiting tints ranging from ivory-through-beige-through-tan-to-brown, depending upon the shade sought, and demonstrating a Fe.sup.+3 reading between about 6.5-9 consisting essentially, expressed in weight percent on the oxide basis, of about______________________________________ SiO.sub.2 64.5 .+-. 2.0 Al.sub.2 O.sub.3 6.25 .+-. 0.5 Na.sub.2 O 3.0 .+-. 0.5 K.sub.2 O 3.0 .+-. 0.5 MgO 1.25 .+-. 0.3 B.sub.2 O.sub.3 4.5 .+-. 0.7 F 3.25 .+-. 0.5 CaO 14.5 .+-. 1.0 NiO 0.02 - 1.

Abstract: There is disclosed an integral vitreous article composed of an opacified interior portion encased within a surface layer of glass that is transparent except for an opacified zone of predetermined configuration. The article may be produced by momentarily contacting an exposed surface on a molten glass charge with a chilling member before forming the glass.

Abstract: The instant invention is directed to the production of spontaneous opal glass compositions which limit the generation of CaF.sub.2 and crystals having a xonotlite structure therein when heat treated at temperatures higher than the annealing point, but lower than the softening point of the glass. The glasses consist essentially, as analyzed in weight percent on the oxide basis, of about:______________________________________ SiO.sub.2 64.5 .+-. 2.0 Al.sub.2 O.sub.3 6.25 .+-. 0.5 Na.sub.2 O 3.0 .+-. 0.5 K.sub.2 O 3.0 .+-. 0.5 MgO 1.25 .+-. 0.3 B.sub.2 O.sub.3 4.5 .+-. 0.7 F 3.25 .+-. 0.5 CaO 14.5 .+-. 1.

Abstract: The present invention is concerned with the production of spontaneous opal glasses which, after thermal tempering, demonstrate a dense coloration ranging from ivory through yellow-beige to tan to a grayish-brown appearance, consisting essentially, by weight on the oxide basis, of 8-9% Na.sub.2 O, 2-2.5% K.sub.2 O, 5-6.5% CaO, 8-10% ZnO, 1-2% B.sub.2 O.sub.3, 10-11% Al.sub.2 O.sub.3, 3-4% F, 0.005-0.1% NiO, 0-2% CeO.sub.2, 0-4%TiO.sub.2, 0.5-6% CeO.sub.2 +TiO.sub.2, 0-0.5% As.sub.2 O.sub.3, and 57-61% SiO.sub.2.

Abstract: Glasses in the Li.sub.2 O-Al.sub.2 O.sub.3 -SiO.sub.2 -MgO-ZnO-TiO.sub.2 composition field, additionally containing PbO and/or one of B.sub.2 O.sub.3, Na.sub.2 O and P.sub.2 O.sub.5 are rapidly crystallized to beta-spodumene glass-ceramics at temperatures not exceeding 1000.degree. C. to provide white, opaque glass-ceramic products exhibiting both low thermal expansion and good chemical durability.

Abstract: This invention relates to the production of essentially transparent glass-ceramic sheet useful as surfaces for smoothtop cooking stoves which will display a warm brown coloration sufficiently dark to conceal the heating element when not in use, but permitting visible observation thereof when in operation. The products consist essentially, on an analyzed basis, of 2.5-4.5% Li.sub.2 O, 1-2% MgO, 1-2% ZnO, 19.5-21% Al.sub.2 O.sub.3, 66.5-68% SiO.sub.2, 4-5% TiO.sub.2, and 0.02-0.2% V.sub.2 O.sub.5.

Abstract: Glasses in the Li.sub.2 O--Al.sub.2 O.sub.3 --SiO.sub.2 --MgO--ZnO--TiO.sub.2 composition field, additionally containing PbO and/or one of B.sub.2 O.sub.3, Na.sub.2 O and P.sub.2 O.sub.5 are rapidly crystallized to beta-spodumene glass-ceramics at temperatures not exceeding 1000.degree. C. to provide white, opaque glass-ceramic products exhibiting both low thermal expansion and good chemical durability.

Abstract: Photosensitive laminated glass useful for providing strong, lightweight glass articles incorporating integral surface decorations resistant to mechanical and chemical deterioration in use are described.

Abstract: There is disclosed a method of making composite glass tubing, and a molten glass feeding apparatus uniquely designed to carry out such method. The feeder apparatus comprises concentrically-arranged cylindrical containers, a blow tube located within the central container, and a plug member mounted on the base of the blow tube. The bottom portion of each cylindrical wall is downwardly and inwardly directed to provide restricted annular bottom openings. The bottom edges of the cylindrical walls and of the plug are positioned in such relation to each other that orifices are provided through which annular streams of molten glass may flow and contact adjacent streams in the fluid state, thereby forming composite glass tubing having at least three layers.

Abstract: Subsurface-fortified glass laminates exhibiting improved breakage characteristics and increased resistance to delayed breakage are described. Such laminates have particular utility in the fabrication of glass tableware.