Will a 2K+ Lumens generate enough heat to combust a thin piece of paper.

Off-topic Chatter
1

Wicked Lasers has a flashlight which @2K Lumens is purported to
Light paper. Cook an egg. Flash Torch

Is it possible they are exaggerating a bit?

At $125-$199 a pop, I can use a BIC for laughs.

& buy some BLF customs with
The rest.

2

Straight from their website, "The FlashTorch is a compact, portable searchlight that is capable of producing an incredible 4100 lumens of intense white light."

That said, they're using a "12v 100W halogen" so I imagine it does start fires. For what it's worth, though, my D4 should be doing over 5000 at turn-on and only causes dark-colored surfaces to smoke, but Texas Avenger put up a video of one of the HaikeLite's lighting a white paper envelope at over 20,000 lumens.

3

Thing is, the flashlights they are selling use halogen bulbs.

That means they emit an insane amount of infrared radiation, basically heat.

So, it’s like having a soldering iron in the form of a light.

4

I have some KANDOlite 50W 6V halogens to play with.

Question is, won’t it melt the (plastic?) reflector if it is producing intense
heat at the IR
Part of the spectrum….

Focusing the output without melting— glass reflector?

TY for all your collective knowledge

5

Plenty of yootoob videos of using a 50W halogen bulb with reflector as an infrared (de)soldering station, so…

6

i almost torched my own shirt with the FW3A, accidentally
it was a nylon/synthetic/athletic type, dark grey
FW3A was about 2” away, accidentally got into turbo
in 2 sec there was smoke

so it basically depends on focus, or area that the 2k lumens are in

2k / square inch will do it

i also have a cheap green laser that is probably less than 10mw, it will burn dry leaves and dark paper
it isn;t 2000 lumens but if the dot is .05” square [roughly] then it would only take 5 lumens to be the same intensity

i THINK 10mw of green is about 65 lumens…?
2 mw would be 13 lumens at that rate
there is a number for watts to lumens, which happens to be pretty accurate at the color of a green laser

wle

7

Mmm, something tells me that’s not the best way to get “smokin’ hot abs”…

8

Yeh. Good thing things didn’t go (further) south…. ouch

Sounds like I need a SW3A in my pants

9

This.

  • LED lights emit almost all of their light in the visible spectrum. The LED also produces a lot of heat, but that heat comes out the back of the LED and heats up the flashlight body. It isn’t radiated out the front with the beam.
  • Halogen bulbs are less efficient and produce even more heat. But that heat is produced mostly in the form of infrared radiation (heat) that radiates out the front. Basically a 4100 lumen halogen light should be much better at starting fires than a 4100 lumen LED light.

Even so, it’s quite possible to start a fire with an LED light like the Emisar D4 outputting 4000 lumens.

10

even a cheap legal laser can set thin dark combustible stuff on fire, pop balloons, etc.

esp if it is powered by 18650, and may be above its legal max anyway

i think the cheap ones frequently are

i;ve also had some of them become fritzy from what i thought was normal use, but may have been driven out of spec, or just poorly designed [same thing]
they go dim, the beam gets out of shape, intermittent brightness shifts, etc

i also had one burn its own ‘holographic filter’ up
but that may have been a blue one, which is definitely out of bounds on power….

wle

11

Has anyone tried using a magnifying glass to focus a flashlight as a firelighter? Like people do with the sun?

12

No, doesn’t work all that well due to physics.

Why?

1. Sunlight not only includes visible light, but also IR light and some UV light. So total energy density is lower.
2. How lights focus.

13

Thanks, interesting to know :+1:

14

Here is a cool xkcd "what if" about using moonlight to start a fire (spoiler: it doesn't work) but it does get into the related physics in an easy-to-understand way

15

Thanks, Scallywag, that was a good read!