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Behavior of Glass at Elevated Temperatures

NCJ Number
Journal of Forensic Sciences Volume: 37 Issue: 5 Dated: (September 1992) Pages: 1358-1362
J J Lentini
Date Published
5 pages
This series of tests was conducted to examine the usefulness of crazed glass as an indicator of abnormal fire behavior.
Crazed glass is defined as glass with numerous, tightly spaced random cracks. In a study of multiple fire losses that occurred with the 1991 Oakland, California fire, the author noted the presence of crazed glass in 12 of 50 residences examined. More crazing of glass appeared to occur around the edge of fire-damaged neighborhoods than in the center, suggesting that fire suppression efforts may have caused crazing. To determine if crazing could be induced by rapid heating or rapid cooling, tests were conducted using four regimes: slow heating to 800 degrees C, rapid heating to 800 degrees C, heating in a propane flame, and heating to low fire temperatures. Despite widely held beliefs that glass crazing results from exposure to rapidly increasing temperature, test results showed that glass does not craze except when its temperature is decreased rapidly. Because crazing is actually due to rapid cooling rather than rapid heating, it is likely to be a much less significant indicator of a fire's behavior than previously thought. 6 references and 4 figures