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Exploding glass coffee table

  1. May 31, 2007 #1
    I had a glass coffee table, it was 12mm thick (approx 1/2 ")
    I had this table for approx 5 months when one night, it just gave off a bange and collapsed (I wasn't in the process of placing anything on it, etc, it had no chips). Some small fragments were embeded into my wife and my hands. The only explanation I can think of is that as it was 1.2M from a heater (approx 4 feet). The heat from the heater caused unequal thermal expansion one one side, and the stresses resulted in the coffee table table exploding. The glass wasn't toughened (it broke into normal shards like std annealed / float glass). The manufacturer stated that the glass is slowly cooled after they bend it to form the table.
    The question I have is
    1- is it possible fro this to have occured in a normal domestic environment ?
    2- is the thermal expansion the likey cause ?
    3- if it was toughened glass, could this have been avoided, or be less likely to occur?
    The company that made the table said this is an impossiblity !
  2. jcsd
  3. May 31, 2007 #2
    Hi Veejo,

    How large is your table? the larger the easier to get a bange i think.
    1. It is not possible for this to have occured in normal domestic environment, with some exceptions like heat source (in your case).
    2. Surely it is thermal expansion causing that. Glass has very low thermal conductivity. 1 meter is quite near and the temperature can be very high in one side. That heat is mainly IR so it can not transmit to the other side.

    3. Clear off the fire/heater
  4. May 31, 2007 #3
    the size of the table was 126cmx72cm (top) 2 sides of 40 cm, and 12 mm (1/2" thick. A fairly large size, 125cm is about 4 feet, that's why I thought expansion and low termal conductivity could be one explanation. I hadn't thought about the IR heat issue, I thought uneven heat might have been caused by warm air hitting the leading edge, and rising, and so not cooling the fair table edge. Uneven heat in any case.
  5. May 31, 2007 #4
    If I had to throw in a guess it would be that there were air bubbles in the glass and they are what expanded at a different rate than the glass and cracked.

    Also if the glass had a metal frame, they may have put the frame on too soon during cooling and preloaded it with stress.

    CraigD, AMInstP
  6. May 31, 2007 #5
    So I can guess your table was cracked because of the heater. It's all because of the heat radiation, not the hot air (or very little effect). If you stand in front of the heater about 1 m away, your face must feel the hot beam, not just the air. Those beams are mainly IR.
    You can test this by placing the remained part of the table about the same distance from the heater for quite a time (the whole day) and then touch the side facing the heater, it must be very hot ?
  7. May 31, 2007 #6


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    Science Advisor

    How is the glass held in the table? It is possible that the heat was only partially to blame. Depending on the temperature of the heater, you may have simply heated the glass to expand and the constraint of the glass in table caused the breakage due to lack of ability to move.

    The really important question is where do you live that allows a manufacturer of a glass top table to make one out of a non-safety glass? That is a product liability case just waiting to happen.
  8. Jun 6, 2007 #7
    It is a glass table, a sheet that is bent, so metal support isn't an issue. I'd say the problem is infra red from the heater heating the edge. Infra red travels in straight beams so it would heat the edge much more than other parts of the table, hence uneven expansion.
    I contacted the manufacturer (I'm in Australia), whose response is that they aren't legally obliged to ensure that the glass is heat treated, toughened, or otherwise designed to ensure this can't happen. In Australia we have standards to ensure glass attached to buildings, or in walkways is treated to ensure thermal expansion will not cause failure if there is a likey hood of thermal changes causing failure. It seems the table is pure annealed glass, and because it's not attached to a building, is exempt from regulations.
    I've lodged this oversight with the govt consumer bureaus' safety divison. A case of a manufacturer meeting their minimum legal obligations vs world best practices.
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