emissivity(?) of molten lead

[tanelorn]

Hi Folks,

I spent about 45 minutes using my google-ese, and I wasn't able to find the information I was looking for about lead.

The scale for iron is easily found that shows at what temp iron glows what color. I'm looking for something similar for lead.

would someone please point me in the right direction?

Thanks in advance.


Kind regards,
T

[Crazycowbob]

I'll have to dig up my CRC when I get home, so I could have this totally wrong, but I think lead evaporates long before it gets hot enough to have a significant change in color.

[tanelorn]

thanks for looking into it!!

much appreciated.

Kindest regards,
T

[Gilmar]

I'll have to dig up my CRC when I get home, so I could have this totally wrong, but I think lead evaporates long before it gets hot enough to have a significant change in color.

Drat! Now I may have to modify my plans to pour red-hot molten lead over the parapets onto the attacking rabble below.

[casebro]

Wouldn't anydamnthing that gets heated to 450f give of infra red? More so if liquid- the phase change takes more energy.

[Dilb]

The neat thing about blackbody radiation, as you would get from molten lead or iron, is that the colour almost completely depends on the temperature. According to whatever Google brings up, glowing red occurs for temperatures between roughly 1000K to 1400K. Lead melts at 600K, but doesn't boil until 2000K, so it should easily be possible to pour glowing, molten lead onto whoever is cluttering your parapets.

[Gurdur]

...,.so it should easily be possible to pour glowing, molten lead onto whoever is cluttering your parapets.

Bloody expensive in the end though. Pitch is far easier and cheaper.

[PixyMisa]

Lead melts at 600K, but doesn't boil until 2000K, so it should easily be possible to pour glowing, molten lead onto whoever is cluttering your parapets.
Woohoo!

Well, that's next Halloween sorted out at Pixy Central.

[rehn]

Emissivity tells me the relation between reflected and transmitted radiation from a surface.
In the case of molten lead this must vary depending on how "shiny" it is. If it is free from oxide I image the the emissivity must be quite low.

http://en.wikipedia.org/wiki/Emissivity

The colour of the transmitted radiation is almost entirely a function of temperature so if that is what you want you might as well use the tables for steel,
or this:
http://en.wikipedia.org/wiki/Image:Blackbody-colours-vertical.png

In the case of molten lead (~600K ) all radiation is within IR. ( the phase change makes no difference )
The intensity if transmitted radiation increases with the 4:th power of temperature.

[tanelorn]

Thanks everyone,

I can see that I didn't word my question well enough.
I was thinking more along the lines of visible wavelengths.


In the case of molten lead (~600K ) all radiation is within IR. ( the phase change makes no difference )
The intensity if transmitted radiation increases with the 4:th power of temperature.

so if this statement is true, it won't "glow" per-se...??? (unless you can see in the infrared. which unfortunately, I can't... :( . ) I can see from the responses that I didn't make myself clear. I'll read the links you posted as well as the others that have been posted.

I'm a little out of my element (heh) and I appreciate the responses.
Thanks,

Kindest regards.
T

[Cuddles]

so if this statement is true, it won't "glow" per-se...??? (unless you can see in the infrared. which unfortunately, I can't... :( . ) I can see from the responses that I didn't make myself clear. I'll read the links you posted as well as the others that have been posted.

Not quite. Lead melts at 600K, but that does not mean all molten lead is at 600K. If you heat it up so it is only just runny then yes, almost all the radiation will be infra-red. On the other hand, if you heat it up to just under 2000K it certainly will glow. And of course it will glow at higher temperatures, but lead gas is probably a bit harder to play with.

Edit: The Wiki (http://en.wikipedia.org/wiki/Black_body) article on black body radiation explains it quite well. The important thing to remember is that the actual material doesn't really matter, the only important thing is the temperature.

[Dabljuh]

That's not quite true. The material *does* matter. Some materials, or rather, objects, are better blackbodies than others. I learned this when investigating the 9/11 conspiracies (Rumsfeld totally did it), this professor compared molten aluminium and molten iron at 2000°F, and found that molten aluminium does not really glow even at 2000°F, while molten iron glows brightly.

If both materials were perfect blackbodies, they would of course give off the perfect, identical blackbody radiation. But materials, and also objects, have different properties when it comes to blackbody-ness.