[TheForge] IR emissivity #2

[peter fels]

Sorry about the previous goof up.

Try again here.
I got my new Chinese IR gun Fri and it's neat!..Goes to 1250*.
Pointed it at the home made fireplace when it was really cooking and the hot spots were over 750*F.
Much more than i would have guessed.

Reading the instruction sheet...typically awkward and ambiguous Chinese translation...i ran across the matter of emissivity.
It seems that different metals radiate very different % of their IR heat! 
And it seems that the surface composition, oxidation and roughness also strongly influence the reading.
My intent in getting the IR gun was as an adjunct to  hot forging non-ferrous metals. It is adjustable for different emissivity values.
It seems that the emissivity of aluminum and silver is dinky and copper alloys also have diminished emissivity and so on.
The charts i found seem to be all over the place for values.
So, i'm guessing that functionally, I'll have to heat the metal to where it craps out , measure that temperature, and stay under it.

What am i missing here?