Defect glass

R. Kirchheim. Interstitial diffusion in glass. Defect and Diffusion Forum, 95-98 1159-1164, 1993. 

Fanderlik M., Glass Defects (in Czech), SNTL, Prague, 1963 (Vady skla, SNTL, Praha). Fanderlik M., The Structure of Glass (in Czech), SNTL, Prague, 1971 (Struktura skla, SNTL, Praha). 

Fast-mixing oxy/fuel burners can overheat the glass locally, leading to numerous glass defects such as cord and seeds. On the melt surface, foam formation or reboil is... 

Dimensions may be measured automatically by either gauges or instruments. Typical gauges are shown in Figure 6.18 and are detailed in Appendix 6.1. Glass defect terminology is given in Appendix 6.2. Appendix 6.3 gives a typical bottle specification. 

Two refractory groups will be considered in this paper, AZS based and alumina based. For AZS based products, refractories made with fusion-casting, dry pressing, and vibro-casting processes will be considered. The Alumina based products include only fusion-cast and vibro-cast rehactories. Although the bulk of the paper will focus on performance of these materials in a corrosion test, some information on glass defect potential will also be provided. 

Whereas fused-cast alpha-beta alumina refiactories have been used in the feeder chaimel application for many decades, the use vibro-cast alumina in feeder channels is more recent. In this application, the key performance criteria include glass melt contact corrosion resistance and glass defect potential. Service temperatures are expected to be in the range of 12S0 C - I3S0°C. 

Glass industry can benefit from thorough evaluation of post-campaign samples of bonded AZS pavers, vibro-cast AZS and alumina products. Such a study, coupled with glass defects data from furnace campaign, can be immensely useful in determining the cost vs. benefit of using lower-cost refractories. 

Sometimes, during batch melting and fining, the gas huhhles do not hurst when they reach the melt surface, but rather create a foam layer. Such foaming adversely affects heat transfer into the melt and can lead to glass defects, and so should he avoided hy whatever means is effective. 

Melter-Created Glass Defects. Despite best efforts to generate a perfectly uniform glass melt, within any melter there are naturally occurring processes that oppose those efforts. These include refractory corrosion (dissolution), electrode corrosion, and preferential volatilization of some species from the melt surface. These produce localized and sometimes more global deviations from the desired glass composition. Localized composition deviations lead to inhomogeneities in the product, called cord and striae. 

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