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!!
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.
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.
Help with outdoor fabrics...?
scorpiowom
I am repainting a metal outdoor table and recovering the seats of the matching chairs. I really want a black and white pattern, but all the outdoor fabrics I am finding are either just single colors or they are ridiculously expensive and have to be special ordered. Are there any treatment products out there to use on cottons or other fabrics that might work or any online resources for ordering cheaper outdoor fabrics?
Answer
I had a bistro set with 4 chair seats I wanted to recover inexpensively. I bought a large (52" x 120") vinyl-coated fabric outdoor table cloth for less than $12 (it was either at TJ Maxx or the sale bin at Pier One) and cut the covers from it. I had more than enough left over to make matching placemats, too. The fabric seemed to hold up well to weather and sunlight. (don't know for how long -- I sold the set after 2 years.)
I've also covered outdoor cushions with just regular fabric. Drapery yard goods or even fabric shower curtains are cheap sources -- I've even used brightly printed bed sheets (that's what is covering my porch couch right now.) I wrap the cushions with plastic first, so they won't soak through if the chairs get left in the rain, then put the fabric covers over that. They can be removed and machine washed.
If you have a choice, pick polyester or other fabrics instead of cotton or nylon. Poly is more resistant to dying so the dyes that are used for polyester tend to hold up better to fading in the sun. It also resists staining and mildew better than cotton or nylon, at least in my experience.
You can also get a paint-on or spray tent waterproofing liquid at some large camping good stores, but it will tend to discolor some fabrics and it really does not make them completely waterproof.
I had a bistro set with 4 chair seats I wanted to recover inexpensively. I bought a large (52" x 120") vinyl-coated fabric outdoor table cloth for less than $12 (it was either at TJ Maxx or the sale bin at Pier One) and cut the covers from it. I had more than enough left over to make matching placemats, too. The fabric seemed to hold up well to weather and sunlight. (don't know for how long -- I sold the set after 2 years.)
I've also covered outdoor cushions with just regular fabric. Drapery yard goods or even fabric shower curtains are cheap sources -- I've even used brightly printed bed sheets (that's what is covering my porch couch right now.) I wrap the cushions with plastic first, so they won't soak through if the chairs get left in the rain, then put the fabric covers over that. They can be removed and machine washed.
If you have a choice, pick polyester or other fabrics instead of cotton or nylon. Poly is more resistant to dying so the dyes that are used for polyester tend to hold up better to fading in the sun. It also resists staining and mildew better than cotton or nylon, at least in my experience.
You can also get a paint-on or spray tent waterproofing liquid at some large camping good stores, but it will tend to discolor some fabrics and it really does not make them completely waterproof.
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Title Post: What would cause a glass outdoor table top to explode spontaneously?
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