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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

#121

Post by buserror »

shagie wrote: post #91
buserror wrote: post #18

Earlier quoted context omitted.

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...

One of the photographers that I'm intrigued by is Michael Wesely ( https://en.wikipedia.org/wiki/Michael_Wesely ) who takes ultra long exposures (a two week long exposure is "short" - his flower photographs are in that range). The museum of modern art was about two years. http://www.amusingplanet.com/2010/08/unusually-long-exposure... You can see the tracks of the days and the cloud cover in those photographs. Note t…

Thanks for the reminder on the reciprocity rules! I used to take super-long exposure with my 4x5/10x8 view cameras as well... basically after a few minutes, it doesn't /really/ matter anymore so stop counting in minutes/seconds, more in teacups+newspaper pages :-) I always loved the tonal range you get on way, WAY overexposed film.

Re: An Ikea Bowl Has Been Setting Things on Fire

#122

Post by shagie »

buserror wrote: post #121
shagie wrote: post #91

Earlier quoted context omitted.

One of the photographers that I'm intrigued by is Michael Wesely ( https://en.wikipedia.org/wiki/Michael_Wesely ) who takes ultra long exposures (a two week long exposure is "short" - his flower photographs are in that range). The museum of modern art was about two years. http://www.amusingplanet.com/2010/08/unusually-long-exposure... You can see the tracks of the days and the cloud cover in those photographs. Note t…

Thanks for the reminder on the reciprocity rules! I used to take super-long exposure with my 4x5/10x8 view cameras as well... basically after a few minutes, it doesn't /really/ matter anymore so stop counting in minutes/seconds, more in teacups+newspaper pages :-) I always loved the tonal range you get on way, WAY overexposed film.

Digging up an old page (I am not sure if the film still has that characteristic curve), Provia 100F had some very nice lack of reciprocity failure. http://home.earthlink.net/~kitathome/LunarLight/moonlight_ga... (from http://home.earthlink.net/~kitathome/LunarLight/moonlight_ga... - its an old frames page).

The correction for a 1200 second (20m) exposure on Kodak black and white film was at 12x (for 14400s, 4h). However, the extrapolation for the curve for Provia 100F put the reciprocity failure for 1200s at 2.35 for a 3000 second exposure.

Looking at the methods and results is interesting, though I've gone nearly full digital now.

Re: An Ikea Bowl Has Been Setting Things on Fire

#123

Post by thesz »

tekromancr wrote: post #120
thesz wrote: post #70

Can't help myself: https://www.youtube.com/watch?v=uJuuFLo1a84&t=252s Getting fire with the spoon (!) in Siberia's (!!) Winter (!!!). The sun light is not very bright at that time, just for a note. Sun is about couple tens of degrees above horizon and (infrared) light mostly caught by the atmosphere.

"Sure, it's cold—but to a fire, everything is cold" https://what-if.xkcd.com/155/

My note was mainly about sun ascension, not temperature.

Re: An Ikea Bowl Has Been Setting Things on Fire

#124

Post by dekhn »

ythn wrote: post #90
dekhn wrote: post #74

Earlier quoted context omitted.

I can set a piece of cardboard on fire with visible flames in a few seconds. I carry a small fresnel lens, https://www.amazon.com/3-Pack-Credit-Card-Pocket-Fresnel/dp/...

I still maintain that it is much more difficult to start a fire with a lens or mirror than people seem to think. Post a video of using your fresnel lens on different material types (paper, cardboard, wood, pine needles) and see how quickly you can get a visible flame. I'm betting you won't be able to easily get a visible flame on most materials you try.

it's not hard for me for any of these. But then, I build telescopes and microscopes in my spare time and so I'm quite familiar with getting a good focus.

Re: An Ikea Bowl Has Been Setting Things on Fire

#125

Post by shanev »

camiller wrote: post #95
shanev wrote: post #87

A similar phenomenon causes birds to spontaneously combust when flying near industrial solar power plants: https://www.youtube.com/watch?v=ICLXQN_lURk .

Hmmm.... spontaneous would be without an external source of ignition, which is the solar concentrators of the power plant. Probably more accurate to strike spontaneously and simply say "...causes birds to combust when flying near ..."

Right, but the source of ignition here is invisible to the human eye. So it's bit of a grey area.

Re: An Ikea Bowl Has Been Setting Things on Fire

#126

Post by stcredzero »

Florin_Andrei wrote: post #118
stcredzero wrote: post #97

Earlier quoted context omitted.

But because the risk is so low (it doesn't happen that frequently) many people are completely unaware of the phenomenon. Also, people can't apply what they were supposed to learn in high school physics. It's not only Brazil that has this problem: http://v.cx/2010/04/feynman-brazil-education

> Also, people can't apply what they were supposed to learn in high school physics. Well, it's very rare and therefore you don't think about it. I make telescope mirrors, so I can't be accused of being unaware of the laws of optics. Yet until now I never thought about crystal balls (heck, even acrylic balls) as a potential fire hazard inside the house .

Well, it's very rare and therefore you don't think about it.

Approximately spherical transparent objects are common. Approximately cylindrical and spherical reflective surfaces are common. Situations where you can apply high school physics are very, very common. Most of us just don't, because we're not trained to do so. We're trained to do the homework problems and answer the test questions. But don't we learn this stuff so we can use the knowledge in life?

I can't be accused of being unaware of the laws of optics. Yet until now I never thought about crystal balls (heck, even acrylic balls) as a potential fire hazard

So you're over halfway there. Now we collectively have a chance to learn the meta-lesson about applying knowledge.

Re: An Ikea Bowl Has Been Setting Things on Fire

#127

Post by maxmcorp »

I suddenly smelled smoke one morning and could not figure out where it came frome. Turned out it was a paper napkin i had left in one of those bowls on my kitchen table. And the sun came in through the window in just the right angle. Took me a few minutes to figure out what the reason was.

Re: An Ikea Bowl Has Been Setting Things on Fire

#128

Post by joeframbach »

dsfyu404ed wrote: post #48

I hope they don't change the design. This would be great for camping/hiking/backpacking. Having a bowl that's also capable of starting a fire is a nice extra safety measure and it takes up almost no space because you pack stuff into it.

I can't quite remember the exact make or model, but years ago there was a lightweight folding camp chair which has a removable plastic support. Its shape was perfect for a makeshift arm splint. Many people suggested that this camp chair should be part of their go-to gear. The following year the chair was redesigned without the removable support :(

Re: An Ikea Bowl Has Been Setting Things on Fire

#129

Post by HeyLaughingBoy »

cr0sh wrote: post #115
logfromblammo wrote: post #93

Earlier quoted context omitted.

Unfortunately, my kids already know from watching How It's Made that most wiener-type sausages sold in the US are fully cooked at the factory, and when you "cook" them at home, you're just heating them up. One would just eat it without bothering with the foil for even one minute, and the other doesn't eat hot dogs at any temperature. I remember, as part of a wilderness survival challenge, being told to eat some break…

> that the tinder had KMnO4 in it, and the arrow popped a hidden balloon with some glycerol For those that don't know, KMnO4 is also known as potassium permanganate: https://en.wikipedia.org/wiki/Potassium_permanganate As noted in that wikipedia article, when combined with glycerol or other glycerin containing products (like automotive antifreeze) it can also be used as a fire starter. It can be easily found online o…

You just had to post that, didn't you!!!

Got a bottle of KMnO4 next to my iron filter and at least one jug of glycol antifreeze in the garage.

Guess what I'm doing when I get home :-)

Re: An Ikea Bowl Has Been Setting Things on Fire

#130

Post by classybull »

Camillo wrote: post #114
jefurii wrote: post #101

Earlier quoted context omitted.

> The same phenomenon occurs with glass spheres. Also clear water bottles (filled with water). In 1991 there was a brief period where homeowners all over Japan were putting clear PET bottles (PolyEthylene Terephthalate) at the edge of their properties because it was asserted on some talk show that the sparkles would keep animals away. This ended abruptly when a series of fires were started by the bottles.

Some people still do it. I've seen it this year in Akasaka.

Its a fairly common thing in restaurants, at least in the South, to hang outside clear plastic bags half full of water from any sort of awning or overhang, especially around dumpsters.

Supposedly it confuses flies and they'll leave the area alone. I've never seen any evidence of this.

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