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Burning white objects....

Schrecken_Licht

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I was wondering exactly what amount of power is need to burn white objects, like paper, with a visible light or near IR-UV laser. None of my visible light lasers can do it, and neither can my YAG, despite the fact that it has roughly equivalent to 3 watts of power. Still it behaves pretty much (other than being pulsed) like a visible red laser, burning only dark colored things.


My CO2 can of course do it, but that's mainly because color isn't an issue at that mid-far IR wavelength. Everything (well, most everything) absorbs the beam.

But say you have a 532, a 473, or a 660nm laser of high power (running CW), what power would you have to have at minimum to torch something white? This is the point where the laser's power overcomes the reflectivity of the material (the reason why YAGs can cut and weld metal at very high power).

Perhaps the guy with the 4 watt argon can answer this? I don't know who else here has a visible laser of a few watts. How about multi-watt IR diodes? What power do you need to burn white stuff with those? Has anyone here done it?
 

Murudai

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Do you mean burn or ignite?

My 200mW dilda can't, but my 290mW red from jayrob can JUST burn white paper. Sometimes it can, sometimes it can't. I'm guessing minor imperfections in the paper can start it burning.
 

GooeyGus

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200mW of 405nm has no problem with white paper or objects. Even at 100mW i'm sure 405nm will be able to burn white paper when focused correctly.
 

Murudai

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:eek: Damn!

My 70mW blu-ray JUST managed to burn some white paper. It was only a little pin prick, but it burnt through it :eek:

Man, I can't wait for this technology to develop. I want me a 300mW blu-ray burner ;D
 

cybob101

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stf 300mw i heard a 1wat br diode is coming out ;D ;) for those around me if i ask for a permant marker start running :eek:

poke with marker then focus br on them = :p :-[ :-[ :-[ :-[ :-[
 

Switch

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I don't think that at some power level the laser just "overcomes" the reflectivity.White absorbs too, but a very small percentage.The power needs to be high enough so even that small percentage will be enough to burn.If we'd know the absorbance rate of black and white paper, it would be pretty easy to calculate. :p
 

rkcstr

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My ~100mW violet diode with burn white paper as well... I was thinking it maybe had to do with the fluorescence?  Since the paper is absorbing the light, which causes it to fluoresce, it only takes so long until that absorbance causes enough heat to burn.  Compared to most other wavelengths which are mostly reflected by white, hence the need to color them darker.
 




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