Method for manufacturing coloured glass-ceramic slab articles from a base mix, comprising the steps of a) preparing a mix comprising a colouring pigment, at least one binder and a preponderant amount of a glass frit having a specific composition, b) distributing the mix in a forming support, c) compacting the mix, d) drying the mix, e) sintering the compacted and dried mix by firing to obtain a slab article, and f) cooling the articles under conditions such as to prevent—even partial—devitrification and/or crystallization of the glass frit. The invention also relates to a glass frit for manufacturing base mixes and a coloured glass-ceramic slab article obtained from the base mix.

Method for manufacturing coloured glass-ceramic slab articles from a base mix, comprising the steps of a) preparing a mix comprising a colouring pigment, at least one binder and a preponderant amount of a glass frit having a specific composition, b) distributing the mix in a forming support, c) compacting the mix, d) drying the mix, e) sintering the compacted and dried mix by firing to obtain a slab article, and f) cooling the articles under conditions such as to prevent—even partial—devitrification and/or crystallization of the glass frit. The invention also relates to a glass frit for manufacturing base mixes and a coloured glass-ceramic slab article obtained from the base mix.

The present application provides transparent glass-ceramics of β-quartz of composition containing a small content of lithium, articles constituted at least in part of said glass-ceramics, glasses precursors of said glass-ceramics, and also a method of preparing said articles. Said glass-ceramics have a composition, free of arsenic oxide and antimony oxide, except for inevitable traces, expressed as percentages by weight of oxides, containing: 62% to 68% of SiO.sub.2; 17% to 21% of AI.sub.2O.sub.3; 1% to <2% of Li.sub.2O; 1% to 4% of MgO; 1% to 6% of ZnO; 0 to 4% of BaO; 0 to 4% of SrO; 0 to 1% of CaO; 1% to 5% of TiO.sub.2; 0 to 2% of ZrO.sub.2; 0 to 1% of Na.sub.2O; 0 to 1% of K.sub.2O; with Na.sub.2O+K.sub.2O+BaO+SrO+CaO<6%; optionally up to 2% of at least one fining agent comprising SnO.sub.2; and optionally up to 2% of at least one coloring agent.

The present application provides transparent glass-ceramics of β-quartz of composition containing a small content of lithium, articles constituted at least in part of said glass-ceramics, glasses precursors of said glass-ceramics, and also a method of preparing said articles. Said glass-ceramics have a composition, free of arsenic oxide and antimony oxide, except for inevitable traces, expressed as percentages by weight of oxides, containing: 62% to 68% of SiO.sub.2; 17% to 21% of AI.sub.2O.sub.3; 1% to <2% of Li.sub.2O; 1% to 4% of MgO; 1% to 6% of ZnO; 0 to 4% of BaO; 0 to 4% of SrO; 0 to 1% of CaO; 1% to 5% of TiO.sub.2; 0 to 2% of ZrO.sub.2; 0 to 1% of Na.sub.2O; 0 to 1% of K.sub.2O; with Na.sub.2O+K.sub.2O+BaO+SrO+CaO<6%; optionally up to 2% of at least one fining agent comprising SnO.sub.2; and optionally up to 2% of at least one coloring agent.

In a process for manufacturing glass, a mixture of solid glass-forming materials may be melted by application of heat from one or more submerged combustion burners to produce a volume of unrefined molten glass comprising, by volume, 20% to 40% gas bubbles. A refining agent may be introduced into the unrefined molten glass to promote gas bubble removal from the molten glass. The unrefined molten glass including the refining agent may be heated at a temperature in the range of 1200° C. to 1500° C. to produce a volume of refined molten glass. The refined molten glass may comprise, by volume, fewer gas bubbles than the unrefined molten glass. A colorant material may be introduced into the refined molten glass to produce a volume of molten glass having a final desired color.

In a process for manufacturing glass, a mixture of solid glass-forming materials may be melted by application of heat from one or more submerged combustion burners to produce a volume of unrefined molten glass comprising, by volume, 20% to 40% gas bubbles. A refining agent may be introduced into the unrefined molten glass to promote gas bubble removal from the molten glass. The unrefined molten glass including the refining agent may be heated at a temperature in the range of 1200° C. to 1500° C. to produce a volume of refined molten glass. The refined molten glass may comprise, by volume, fewer gas bubbles than the unrefined molten glass. A colorant material may be introduced into the refined molten glass to produce a volume of molten glass having a final desired color.

Modified copper chromite spinel pigments exhibit lower coefficients of thermal expansion than unmodified structures. Three methods exist to modify the pigments: (1) the incorporation of secondary modifiers into the pigment core composition, (2) control of the pigment firing profile, including both the temperature and the soak time, and (3) control of the pigment core composition.

Modified copper chromite spinel pigments exhibit lower coefficients of thermal expansion than unmodified structures. Three methods exist to modify the pigments: (1) the incorporation of secondary modifiers into the pigment core composition, (2) control of the pigment firing profile, including both the temperature and the soak time, and (3) control of the pigment core composition.

The present invention relates to semitransparent pearlescent pigments, to processes for producing them, and to the use of such pearlescent pigments, where the pearlescent pigments comprise monolithically constructed substrate platelets composed of a metal oxide having an average thickness of 1 to 40 nm and a form factor, expressed by the ratio of the mean size to the average thickness, of at least 80, which are enveloped by at least one substantially transparent coating A composed of at least one low-index metal oxide and/or metal oxide hydrate, having a refractive index of less than 1.8, and at least one interference layer in the form of a coating B composed of at least one high-index metal oxide, having a refractive index of at least 1.8.

The present invention relates to semitransparent pearlescent pigments, to processes for producing them, and to the use of such pearlescent pigments, where the pearlescent pigments comprise monolithically constructed substrate platelets composed of a metal oxide having an average thickness of 1 to 40 nm and a form factor, expressed by the ratio of the mean size to the average thickness, of at least 80, which are enveloped by at least one substantially transparent coating A composed of at least one low-index metal oxide and/or metal oxide hydrate, having a refractive index of less than 1.8, and at least one interference layer in the form of a coating B composed of at least one high-index metal oxide, having a refractive index of at least 1.8.