A glass-ceramic includes SiO.sub.2 in a range of 40 mol. % to 80 mol. %; Al.sub.2O.sub.3 in a range of 5 mol. % to 20 mol. %; MgO in a range of 5 mol. % to 20 mol. %; and at least one of B.sub.2O.sub.3, ZnO, and TiO.sub.2, each in a range of 0 mol. % to 10 mol. %, such that the glass-ceramic further comprises a magnesium aluminosilicate crystalline phase at a concentration in a range of 5 wt. % to 80 wt. % of the glass-ceramic.

A CuO-containing glass has a refractive index n of at least 1.7, a minimum absorption coefficient in a visible wavelength range from 380 nm to 780 nm is located between 450 nm and 550 nm, a difference of the absorption coefficient normalized to CuO weight percent at a wavelength of 700 nm and the minimum absorption coefficient normalized to CuO weight percent in the visible wavelength range from 380 nm to 780 nm is at least 10/cm. The glass includes the following components (in % by weight based on oxide): 0-70 wt-% La.sub.2O.sub.3, 0-70 wt-% Y.sub.2O.sub.3; 20-70 wt-% a sum of La.sub.2O.sub.3+Y.sub.2O.sub.3+RE.sub.2O.sub.3; 10-40 wt-% B.sub.2O.sub.3; 0-40 wt-% SiO.sub.2; 0-10 wt-% Nb.sub.2O.sub.5; 0-30 wt-% ZnO; 0-20 wt-% ZrO.sub.2; 0-20 wt-% Ta.sub.2O.sub.5and 0.1-10 wt-% CuO. RE.sub.2O.sub.3 includes Ce.sub.2O.sub.3, Pr.sub.2O.sub.3, Nd.sub.2O.sub.3, Sm.sub.2O.sub.3, Eu.sub.2O.sub.3, Gd.sub.2O.sub.3, Tb.sub.2O.sub.3, Dy.sub.2O.sub.3, Ho.sub.2O.sub.3, Er.sub.2O.sub.3, Tm.sub.2O.sub.3, Yb.sub.2O.sub.3, Lu.sub.2O.sub.3 and mixtures of two or more thereof.

The present invention relates to an alkali-free glass substrate in which when the alkali-free glass substrate is melted, and while holding a temperature at 1400° C., reduced in pressure from an atmospheric pressure to 33.33 kPa at a constant pressure reduction rate for 20 minutes and held at 33.33 kPa for 5 minutes, a diameter of a grown bubble is at least 3 times a diameter of an initial bubble. A bubble having a diameter of 0.1 to 0.3 mm contained in a molten glass at 1400° C. before starting pressure reduction is defined as the initial bubble. A bubble after held at 33.33 kPa for 5 minutes corresponding to the initial bubble is defined as a grown bubble.

An embodiment of the present invention relates to a plasma-resistant glass, and a manufacturing method therefor, and the present invention is intended to provide a plasma-resistant glass having improved plasma resistance properties, and a manufacturing method therefor. To this end, the present invention provides a plasma-resistant glass including SiO.sub.2 in an amount of 40 to 75 mol %, Al.sub.2O.sub.3 in an amount of 5 to 20 mol %, MgO in an amount of 10 to 40 mol %, and MgF.sub.2 in an amount of 0.01 to 10 mol %, and a manufacturing method therefor.

The present invention relates to a black quartz glass consisting of a composition comprising 63 to 65 mass % of SiO.sub.2, 18 to 24 mass % of TiO.sub.2, and 12 to 17 mass % of Al.sub.2O.sub.3, wherein the sum of SiO.sub.2, TiO.sub.2 and Al.sub.2O.sub.3 is 100 mass %; and to a method for producing black quartz glass comprising: mixing 63 to 65 mass % of a SiO.sub.2 powder, 18 to 24 mass % of a TiO.sub.2 powder and 12 to 17 mass % of an Al.sub.2O.sub.3 powder, filling the mixed powder into a mold and then melting at a maximum temperature of 1700 to 1900 C. in an oxygen-free atmosphere, and cooling to room temperature to obtain the black quartz glass; and further to a product comprising a black quartz glass member made of the black quartz glass. The present invention allows to provide a black quartz glass which has an excellent light-shielding property, has no risk of causing contamination in a step of using it, has sufficient color uniformity when the size is enlarged, and is capable of producing a large ingot, and to provide a method for producing the black quartz glass with excellent productivity even in the large ingot, and to provide a black quartz glass product made of the black quartz glass.

The glass contains a Ti component in a glass composition, in which a Ti.sup.3+ ion content is 80 ppm or less.

Disclosed are a miserite crystallized glass for an artificial tooth and a method for coloring same, the method enabling a production of a uniform shade without degrading the physical properties of a crystallized glass by means of simply adding a small amount of coloring additive powder when preparing the crystallized glass. A miserite crystallized glass for an artificial tooth according to the present invention is colored with any one of the shades in groups A, B, C and D of the Vita shade guide which is a tooth shade reference. The miserite crystallized glass has a miserite crystal phase as the main phase and comprises a hydroxyapatite crystal phase and a xonotlite crystal phase as additional phases.

An alkali-free glass has a strain point of 650 C. or more, an average coefficient of thermal expansion at 50 to 350 C. of from 3010.sup.7 to 4510.sup.7/ C., and a temperature T.sub.2 at which a glass viscosity reaches 10.sup.2 dPa.Math.s of from 1,500 to 1,800 C. The alkali-free glass contains, as represented by mol % based on oxides, SiO.sub.2: from 62 to 70%, Al.sub.2O.sub.3: from 9 to 16% B.sub.2O.sub.3: from 0 to 12%, MgO: from 3 to 10%, CaO: from 4 to 12%, SrO: from 0 to 6%, and Fe.sub.2O.sub.3: from 0.001 to 0.04%, provided that MgO+CaO+SrO+BaO is from 12 to 25%. The alkali-free glass has a -OH value of from 0.35 to 0.85/mm.

The subject matter described herein includes a method of manufacturing colored borosilicate glass including, preparing a raw material composition to form a homogenous powdered mixture, placing the homogenous powdered mixture in a container, heating the mixture to a temperature of 2500-3000 F., charging the container with additional homogenous powdered mixture until the container is full, melting the homogenous powdered mixture until it forms molten borosilicate glass, and refining the molten borosilicate glass between 2800-3200 F. to allow air to escape and the glass to fully homogenize.

Disclosed are a wollastonite crystallized glass for an artificial tooth and a method for coloring same, the method enabling a production of a uniform shade without degrading the physical properties of a crystallized glass by means of simply adding a small amount of coloring additive powder when preparing the crystallized glass.