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Thursday, June 5, 2014

What would cause a glass outdoor table top to explode spontaneously?

Q. This happened a couple of weeks ago and when we found it the glass was shattered into hundreds of tiny pieces and was making a crackling noise. There were no sudden changes in temperature and it was not struck by any type of missile.
Very strange!!


Answer
Even without a sudden change in temperature a glass table top could "explode", especially if it was fitted or held in place with screws or other structures that ran through holes in the glass.
Assuming it was a glass/metal table, heating (by sunlight) could have caused differential expansion of the glass and metal. This could have caused the metal to expand in the screw-holes and crack the glass.
Another process that may have happened (and both may have happed simultaneously) would be for the table or table top to expand in a way that put tension on the glass table top.

Glass is a "fragile" material (this is the technical term, not the common one). A fragile material cannot deform, so if the tension exceeds the material resistance it cracks (sometimes in a spectacular way, as in your example).
The opposite of "fragile" is "ductil", a material that is able to deform under tension (like metal). Within limits, the material is able to deform and return to its original shape (like a rubber band). Above that limit the material deforms permanently, like a crushed Coke can.

The fact that the glass pieces were "crackling" suggests termal expansion caused tension in the glass past its resistance limit and it cracked. Because there were no previous cracks or defects in the glass (i.e., weak spots) the whole piece suffered sudden "catastrophic failure" (another technical term from materials science). Once the tension released, the broken pieces were returning to their original configuration macking the crackling noise.
This is a bit like the sounds you can ear from ice when you drop it on your juice glass. Sometimes you also get the ice cubes to crack.

Where can i find a large outdoor patio table with solid, sturdy legs?




jc


All of the tables i've found are hollow metal and poorly made. They bend too easily and don't stay perpendicular to the ground. Need indoor dining table quality, but weather proof and big. Thinking marble or granite. Any suggestions?


Answer
If you are looking for solid sturdy outdoor table, maybe you can consider buying these 3 kinds of patio table, Iron patio table, teak patio table or wood patio table with stone leg.

First and second type of patio table you can find it on eBay, Amazon and other online store. The last one, you need to customize desktop and stone leg in different place.

If you do not have space to store your patio table, and you do not move your patio table often, you can consider buying a large waterproof outdoor patio furniture cover to cover your patio table when you not use it.

Outdoor patio furniture covers could keep your patio table from dust, rain, bird droppings and so on. It will decrease times of cleansing for you.




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