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What is the required mW of a blue laser to burn dark colored paper?

NotPig

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I’m new to lasers and trying to find what mW is required for blue lasers to burn paper.

edit: I currently have a 150 mW 445 nm blue 304 laser from Sanwu lasers
 
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brendon7358

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White paper probably 300-500mW. Black paper probably 75mW will make it smoke. Igniting paper if you take something printed on normal printer paper and burn the back text can be done with 200mW but takes some effort. All of these assume the laser is focused and held still.

Wavelength (color) isn't super important for dark colors but will make a big difference with lighter colors or colors the same as the laser.

Watch these videos
Part 1
Part 2
 

NotPig

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White paper probably 300-500mW. Black paper probably 75mW will make it smoke. Igniting paper if you take something printed on normal printer paper and burn the back text can be done with 200mW but takes some effort. All of these assume the laser is focused and held still.

Wavelength (color) isn't super important for dark colors but will make a big difference with lighter colors or colors the same as the laser.

Watch these videos
I just bought another one on sanwu coming in 7-15 days and it’s a red 200 mW do you think that’s enough to burn white paper?
 

brendon7358

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I just bought another one on sanwu coming in 7-15 days and it’s a red 200 mW do you think that’s enough to burn white paper?
Unless you point it a black text, no. The higher the wavelength the more sensitive it is to what color the thing your burning is. So therefore red is pretty much the worst choice.
 

NotPig

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Unless you point it a black text, no. The higher the wavelength the more sensitive it is to what color the thing your burning is. So therefore red is pretty much the worst choice.
So if I get a 100 mW violet it should be able to burn paper easily
 

GSS

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I think your Sanwu 304 is a 405nm violet.
Unless Sanwu is doing something new??

Edit: My bad I guess Sanwu is offering 304's with a 445:unsure:
405's will focus to a tighter spot so just maby it will burn paper a little..
 

paul1598419

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White paper doesn't catch fire nearly as easily as brown paper from bags. Years ago when I was lighting paper on fire I often used brown bag paper because it reflects light far less than white paper. Even a 2 watt laser at close range is not always enough to catch white paper on fire.
 

steve001

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Way back when red laser pointers were the only pointers, there was a site demonstrating how to burn with such a pointer. The only modification was optical manipulation of the beam.
 




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