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An Ikea Bowl Has Been Setting Things on Fire

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Re: An Ikea Bowl Has Been Setting Things on Fire

#11

Post by masklinn »

symmetricsaurus wrote: post #4

It concentrates the sun from what I could understand from the article. Should work the same for any spherical bowl (parabolic would work even better) that is shiny enough.

The curvature of the bowl would also influence the "focus point", apparently Blanda is curved in such a way that the mirror's focus point is within the bowl, thus being able to set its contents on fire (in the same way the walkie talkie is curved such that its focus point is the focus point is on the sidewalk opposite the building)

Re: An Ikea Bowl Has Been Setting Things on Fire

#12

Post by Freak_NL »

The same phenomenon occurs with glass spheres. If you think about it it is obvious enough (most people are familiar with how a magnifying glass concentrates the ray of the sun in a single spot), but it is something people tend to overlook when employing glass spheres as elements of your interior design — e.g., glass door knobs, large marbles, and decorative knick-knacks (which people have a tendency to place on their windowsills).

Every once in a while a house fire is started because the sun sat at just the right angle at a certain time of the year, placing the focal point on the curtains. But because the risk is so low (it doesn't happen that frequently) many people are completely unaware of the phenomenon.

Re: An Ikea Bowl Has Been Setting Things on Fire

#13

Post by gebruikersnaam »

symmetricsaurus wrote: post #4

It concentrates the sun from what I could understand from the article. Should work the same for any spherical bowl (parabolic would work even better) that is shiny enough.

It's a known way of cooking[0], saw them in Tibet years ago.

[0] https://en.wikipedia.org/wiki/Solar_cooker

Re: An Ikea Bowl Has Been Setting Things on Fire

#17

Post by masklinn »

jlebrech wrote: post #8

they can change the description to self lighting bbq and give it legs. It's also on my list of things to bring on a desert island.

You'd probably be better off with a magnifying or fresnel lens (or set of lenses), they're available as portable/survival tools (sometimes called "fire lenses" or "burning glass").

Fresnel are convenient as they're available in flexible flat rectangular plastic (e.g. credit-card sized). You lose in image quality so it's not great if you're trying to look at mosses or small critters, but to set stuff on fire it's really great as they're light, easy to pack and can be much larger than glass magnifying lenses (of equivalent or lower convenience).

Re: An Ikea Bowl Has Been Setting Things on Fire

#18

Post by buserror »

Freak_NL wrote: post #12

The same phenomenon occurs with glass spheres. If you think about it it is obvious enough (most people are familiar with how a magnifying glass concentrates the ray of the sun in a single spot), but it is something people tend to overlook when employing glass spheres as elements of your interior design — e.g., glass door knobs, large marbles, and decorative knick-knacks (which people have a tendency to place on their…

Actually one of the official 'old school' tool to measure sun exposure thru the day in meteo stations is a glass sphere with a calibrated piece of paper underneath. Needs to be changed everyday, but the burn mark is quite neatly drawn on the chart.

EDIT: Found it again https://en.wikipedia.org/wiki/Campbell%E2%80%93Stokes_record...

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