Patent 11059739 was granted and assigned to Schott AG on July, 2021 by the United States Patent and Trademark Office.
A sightglass for a stove is provided that has a substrate made of transparent coloured lithium aluminium silicate glass ceramic. The sightglass has a light transmittance of 0.1% to 50%. Standard illuminant D65 light, after passing through the glass ceramic, at a thickness of 4 mm, has a colour locus in the white region W1 determined by the following coordinates in the chromaticity diagram CIExyY-2°: