 | Bob Crager of Lewis Street Glass is a 26 year veteran in the glass business. Lewis Street Glass is a leading Wichita Glass company, serving the entire Wichita/Sedgwick County area since 1919. They do anything and everything having to do with glass, both residential and commercial. They also do Auto glass. They are located at 743 South Market, facing Kellogg on the South, and you can reach them by phone at (316) 263-8259. You can email Bob Crager at bcrager@lewisstreetglass.com |
Glass
2003-11-01 09:16:00
My fireplace doors exploded!
: The glass in my fireplace doors was fine for years and one day it just exploded. Was it defective?
ANSWER: No, the glass probably was not defective. Most likely it was tempered glass (that is glass that has been heated then cooled quickly to strengthen it) which, on occasion, can undergo spontaneous breakage. The same process that makes tempered glass so strong also makes it vulnerable to this type of breakage. The same process that strengthens tempered glass also creates some inherent problems. Through the tempering process, a system of residual stresses is introduced to convert normal flat glass to safety glass when the stress level is high enough. Glass is tempered by heating sized, edged glass in a tempering furnace to approximately 1,200 degrees F, then rapidly cooling, or quenching, the glass to approximately 400 to 600 degrees F. In quenching, air jets quickly cool and set the surfaces, leaving the inner portion of the glass thickness relatively hot and cooling at a slower rate. The surfaces become rigid, but the center is still pliable and contracting as it cools, thus compressing the surface. Compressive residual stresses imposed on the glass surface, which close up any cracks, are balanced by residual tensile stress in the center of the glass. These stresses make tempered glass approximately four times stronger than annealed glass, making it ideal for applications where maximum resistance to thermal and cyclic wind loading pressures is required. In addition, if broken, fully tempered glass breaks into relatively safe, small pieces, rather than shards. However, distortion and point inclusions are a natural part of the tempering process.
