Glass doorknob causes fire

Knob shot 2969722b

A glass doorknob acted as a magnifying glass, focusing sunlight into a burning beam that torched some clothing and set fire to a bedroom in a south London home.

"The focal length from the window was just the right distance and it became the same principle as when you try to set fire to paper with a magnifying glass when you are a child," The London Fire Brigade's Charlie Pugsley told The Telegraph.

Apparently, a crystal ball and a mirror are to blame for similar fires in London this year.

Notable Replies

  1. "The Sinister Ray" - In chapter five of the cliffhanger serial SHADOW OF CHINATOWN (1936), the villainous Victor Poten (Bela Lugosi) positions a hanging spherical goldfish bowl over the head of our unconscious hero, such that the magnified rays of the sun will burn his brain! Will he survive?

  2. My wife made a few crystal balls when she was an art student. These have left scorch marks on wood and cloth surfaces on a couple of occasions (despite being far from optically perfect). Though they've never started an actual fire, I wouldn't rule it out as a possibility.

  3. Glass spheres are used in this way as sunshine intensity trackers; just add a strip of paper in the morning and retrieve it in the evening, the scorch marks are the record.

    I also saw such assembly used for tactical recording of above-ground nuclear explosions. Same principle, the marks then record relative position and intensity.

  4. That's shitty luck, the sun only comes out three times a year over there and each time some poor assholes have their house burn down

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