TV panel glass has very high quality requirements. Today's larger sizes & more stringent quality demands even lower defect levels. One of the major glass defects has been a viscous knot that is often referred to as "cold glass" because of its characteristic appearance of a clear glass piece stuck to or included within the glass panel. Thomson has, in the past, experienced furnace operations where this defect represented the largest loss item for the entire campaign & was considered as the number one glass defect problem. Some of the knots were clear & others had crystals present that contained primary zirconia. A study of the knot compositions found them very similar to that seen at the glass-refractory interface between CTV panel glass and fused AZS refractory. Model studies discovered that the convection flow patterns in the melter were not as expected.
