A method of modifying glass frit involves treating the frit with a grain-boundary-healing compound. The method increases transmission and clarity, and reduces haze of a fired enamel coating made from such modified glass frit as compared to a coating not made from such modified glass frit. The grain-boundary-healing compound influences the chemistry at the grain boundaries to prevent haze. The compound burns out to yield a fluxing material that dissolves alkaline carbonates or bicarbonates on the surface of the glass frit. The dissolved species are incorporated into the enamel coating, thereby promoting the fusion of the glass frit and reducing the amount of haze in the enamel coating. The additives also function to prevent the formation of seed crystals on the surface of the glass frit that may inhibit the fusion of the glass frit.

A process for the preparation of multi-coloured dental restorations is described, in which glasses and glass ceramics with various compositions are given the shapes of dental restorations and colour changes are effected in the glasses and glass ceramics by irradiating them with artificial electromagnetic radiation and subjecting them to a heat treatment.

A black enamel composition includes a glass frit, a black pigment and an organic vehicle, wherein the glass frit includes 50 to 70 wt % of Bi.sub.2O.sub.3, 7.0 to 10.0 wt % of SiO.sub.2, 6.0 to 8.0 wt % of B.sub.2O.sub.3, 10.0 to 15.0 wt % of ZnO, 1.0 to 2.0 wt % of Al.sub.2O.sub.3, 3.2 to 10.9 wt % of the total of Co.sub.3O.sub.4, NiO.sub.2 and Fe.sub.2O.sub.3, based on the total weight of the glass frit, wherein the black pigment is 3 to 10 wt % relative to the total weight of the glass frit.

One aspect relates to a process for the preparation of a quartz glass body. The process includes providing silicon dioxide particles, making a glass melt out of the silicon dioxide particles in an oven and making a quartz glass body out of at least part of the glass melt. The oven has a gas outlet through which gas is removed from the oven, wherein the dew point of the gas on exiting the oven through the gas outlet is less than 0° C. One aspect further relates to a quartz glass body which is obtainable by this process. One aspect further relates to a light guide, an illuminant and a formed body, which are each obtainable by further processing of the quartz glass body.

A lithium aluminum silicate glass ceramic, which, apart from unavoidable impurities, is As2O3-free and Sb2O3-free. The lithium aluminum silicate glass ceramic has keatite as primary crystal phase and a keatite peak temperature TP of the keatite solid solution formation in the range of 980° C. to 1090° C., and the keatite peak temperature TP is determined by dynamic differential calorimetry (DSC) in accordance with DIN 51007:2019-04 at a heating rate of 5 K/min. A ceramization method is also described.

A method for the manufacture of a worktop formed of at least one glass-ceramic substrate with a surface area of greater than 0.7 m.sup.2 in which at least one cycle of ceramization of a glass plate with a surface area of greater than 0.7 m.sup.2 is carried out in a manner where the rate of passage is reduced or the length of the ceramization furnace or the residence time in said furnace is increased.

The present disclosure relates to fusion formable highly crystalline glass-ceramic articles whose composition lies within the SiO.sub.2—R.sub.2O.sub.3—Li.sub.2O/Na.sub.2O—TiO.sub.2 system and which contain a silicate crystalline phase comprised of lithium aluminosilicate (β-spodumene and/or β-quartz solid solution) lithium metasilicate and/or lithium disilicate. Additionally, these silicate-crystal containing glass-ceramics can exhibit varying Na.sub.2O to Li.sub.2O molar ratio extending from the surface to the bulk of the glass article, particularly a decreasing Li.sub.2O concentration and an increasing Na.sub.2O concentration from surface to bulk. According to a second embodiment, disclosed herein is a method for forming a silicate crystalline phase-containing glass ceramic.

Disclosed herein are glass-ceramics having crystalline phases including β-spodumene ss and either (i) pseudobrookite or (ii) vanadium or vanadium containing compounds so as to be colored and opaque glass-ceramics having coordinates, determined from total reflectance—specular included—measurements, in the CIELAB color space of the following ranges: L*=from about 20 to about 45; a*=from about −2 to about +2; and b*=from about −12 to about +1. Such CIELAB color space coordinates can be substantially uniform throughout the glass-ceramics. In each of the proceeding, β-quartz ss can be substantially absent from the crystalline phases. If present, β-quartz ss can be less than about 20 wt % or, alternatively, less than about 15 wt % of the crystalline phases. Also Further crystalline phases might include spinel ss (e.g., hercynite and/or gahnite-hercynite ss), rutile, magnesium zinc phosphate, or spinel ss (e.g., hercynite and/or gahnite-hercynite ss) and rutile.

A method is provided for producing a glass or glass ceramic article that includes: providing a sheet-like glass or glass ceramic substrate having two opposite faces, which in the visible spectral range from 380 nm to 780 nm exhibits light transmittance of at least 1% for visible light that passes from one face to the opposite face; providing an opaque coating on one face where the coating exhibits light transmittance of not more than 5% in the visible spectral range from 380 nm to 780 nm; and directing a pulsed laser beam onto the opaque coating and locally removing the coating by ablation down to the surface of the glass or glass ceramic article, repeatedly at different locations, thereby producing a pattern of a multitude of openings defining a perforated area in the opaque coating, so that the opaque coating becomes semi-transparent in the area.

The invention relates to a coated glass substrate or glass ceramic substrate with resistant, multi-functional surface properties, including a combination of anti-microbial, anti-reflective and anti-fingerprint properties, or a combination of anti-microbial, anti-reflective and anti-fingerprint properties where the substrate is chemically pre-stressed, or a combination of anti-microbial and anti-reflective properties where the substrate is chemically pre-stressed. The coated glass substrate or glass ceramic substrate exhibits a unique combination of functions which are permanently present and do not exert a negative effect on each other.