Zircon cords have been known and referred to in literature for over 50 years, and although they can represent a difficult problem for the glassmaker, the industry does not appear to be any closer to preventing their occurrence. In fact, quite the opposite, there is an impression that there are more and more cords appearing today. Though some may disagree, it is generally accepted that the majority of - or possibly even all - zircon cords originate in the melter. The increase in the use of fused cast AZS materials in the superstructure of modern furnaces may be one reason for the apparent increase in cords, aided by the fact that superstructure temperatures tend to be a little higher than in the past. In this article, the author, Richard Sims of Nikolaus Sorg, offers a solution to the problem.
