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Old 19 October 2007, 09:38 AM
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Default Crystal Ornament Causes House Fire

I've seen this as an urban legend - a glass or crystal ornament refracts sunlight and sets fire to the room. However, this is from today's news (complete with photo):

Firefighters said the crystal ball on a woman's windowsill had refracted the low, strong October sunlight on to the curtains, setting her lounge on fire.

I'm not sure if this is "life imitates myth" or "myth being based on rare real event".
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Old 19 October 2007, 09:53 AM
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I had a giant [knee-height] clear glass whiskey bottle in our yard, filled with water.
By the end of summer there was a strip, almost 1cm deep and 20 cm long charred into the wooden fence behind the bottle.

Needless to say, I moved the bottle out of the direct sunlight!
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Old 19 October 2007, 02:58 PM
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This is definitely possible. There is an instrument used to record sunlight, which consists of a glass ball against a concave surface, and the burn markings were read off it.

Is this also why beer bottles are made of coloured glass, to prevent fires when they are tossed into long grass. I've heard that is the case in Australia.
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Old 19 October 2007, 04:03 PM
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Quote:
Originally Posted by Skeptic View Post
Is this also why beer bottles are made of coloured glass, to prevent fires when they are tossed into long grass. I've heard that is the case in Australia.
Sounds like an UL. AFAIK beer bottles are usually made of brown glass to prevent ageing.
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Old 20 October 2007, 06:50 AM
Troberg Troberg is offline
 
 
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Quote:
Is this also why beer bottles are made of coloured glass, to prevent fires when they are tossed into long grass. I've heard that is the case in Australia
and

Quote:
Sounds like an UL. AFAIK beer bottles are usually made of brown glass to prevent ageing.
Both are right, in a way. Green or brown bottles are used to prevent ageing. It's also tradition, beer is supposed to be in a green or brown bottle.

On the other hand, forest fires are occasionally started by discarded bottles, and colored glass would be less likely to do that. It's not a perfect protection, though, as they can start both through refraction through the glass and reflection in the glass surface. Colored glass only fixes the first problem.
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Old 21 October 2007, 09:31 AM
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Beer bottles in the US aren't all made from colored glass, but even here in the high desert, I can't imagine a discarded bottle starting a grassfire (haven't been here in New Mexico that long yet, but haven't heard of it, either). An angled bottle, one filled with water, or various other shiny yard decorations, maybe so, but never heard of that before, either (until reading marrya's post).

However, I personally know of a crystal that started a small fire, and it wasn't even a real crystal or even cut glass, or an actual deliberate prizm.

When I was a teen (cerca 1970s) in the San Jose, California area, we had a plastic globe with cut sides (no particular geometric shape that I know or can identify - just a cheap trinket) hanging in our kitchen window facing east. It produced little rainbows or other optical effects when the morning sun hit it. One day I noticed a small burn in our curtains, right where light from the "crystal" would have been focused before the curtains were opened. The curtain was not near the stove, and as we rarely fried anything, there no chance of it was caused by a grease splatter (no smokers in the house, either). The burn was pea-sized or smaller, and was smoldered right thru, with charred edges (hence, how we knew it was a burn).

I can't remember all the details from over 30 years ago, such as if we discovered it (or smelled it) immediately, or how long the ball had been hanging in the window. But, thank goodness the curtains were either not very flammable, or that the poor optical quality of the globe delayed the ignition of our curtains while the sun rose high enough to no longer hit our window at the necessary angle. The fabric was at just the right distance from the "crystal" for it to focus just enough light to ignite it, though.

Perhaps the globe was there for as long as it was (before the problem manifested itself) due to the season, and therefore the angle of the sun, and because we usually opened the curtains first thing in the morning.

Just an almost forgotten memory (until reading this OP), but I remember discovering this danger, which is indeed possible, however rare it may be. We felt quite fortunate that the fire was limited to a tiny hole in the kitchen curtains.
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Old 18 November 2007, 09:06 PM
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I had a solid glass ball about the size of an orange that nearly started a fire. I kept it in a room with a western window. One afternoon I smelled smoke. It seemed that the ball was refracting the afternoon sunlight to burn a hole in the cloth between the ball and the stand that supported it. Had the material been more flammable (or stored near something flammable), I can see how it potentially could start a fire.
Note that it had been there some time before the burning incident happened. Maybe the sun caught it at the right angle that day. Or maybe it's a rare thing.
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Old 20 November 2007, 03:23 PM
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Thanks, Namowal, for the add'l story confirming that this can happen. We obviously didn't imagine this!

It may be rare, as you said, but certainly is possible, and there's no way I'm ever hanging any prizm-like objects in the sun again, especially now that I live in the high desert!

Also, welcome to Snopes!
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