Glass doorknob causes fire




The unintended consequences of forgetting a variable in design process. Oops.

There are more cases of such unintended solar concentrators. Entire buildings can serve this purpose.

Another such case here, explanation here.


This story sounds like something Adam Savage and Jamie Hynemann would try to "bust"


I have to admit I'm skeptical too, but it's not completely impossible. I would not be surprised to discover that the homeowner was also a smoker with mild dementia or something.


I would want to ask the owner if he has don't anything blasphemous or heretical in the recent past? I mean... that doorknob wasn't brand-new, was it?


"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?


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.


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.


Imagine what would happen if light from the Walkie-Talkie skyscraper hit one of these knobs!


This happened with a plastic Fresnel lens on the window of our family car when I was a kid. My mom had just bought the car, and a previous owner had stuck a 20x25cm lens on the rear window, probably so they could better notice cars that would otherwise have been hidden by the car's blind spots.

The care was always parked outside, and one sunny caused a 15-cm scorch mark on the top of the rear passenger seat - all the way through the velour upholstery and maybe 1.5cm into the foam. Whatever flames there might have been went out by themselves.


This aberration really is spherical.


We were doing a photo shoot with a crystal ball a few weeks ago and it kept burning people. It melted part of a plastic witch hand and basically just shot death rays everywhere. I was pretty blown away...


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


living in a house with antique glass doorknobs, this is of particular interest to me. we always thought that they stopped making glass handles for doors because they tended to shatter in fires, making them dangerous and impossible to escape. ours aren't spheres, so there's that, but i never thought about them focusing sunlight and starting a fire. maybe that's one of the reasons behind the old-timey faceted doorknobs?


Surely the distance to the window is irrelevant. It's the distance from the knob to the flammable items. Sun rays are pretty much parallel by the time they get here.


maybe, but arson forensics is a pretty advanced field. there's a lot of motivation for arson, and the police and insurance companies have a lot of motivation to identify it. i'm not saying that this was arson, just that we have a lot of skill in this area.

there have been cases of clothes left in a dryer starting a fire. there's enough heat to smolder a piece of lint, at which point it's all over. if there were a splinter in just the right (or wrong) place, a doorknob like this could pretty easily spark it.


There are also cases of oily rags starting fire. A heap of clothes contaminated with oil (the unsaturated triglyceride kind, not as much the mineral kind), and the heat evolved by the slow oxidation of the double bonds can set the heap in fire from within. A bane of varnish painters and massage therapists.

Regarding fires, lots of fun and case studies is in this book.


Yeah, that bugged me too.




This topic was automatically closed after 5 days. New replies are no longer allowed.