I once took one of those infrared heat guns with me to the auto auction

IR radiometer ?

"Heat guns" was a POOR choice of words. The only gun I pack as a Glock. G

Raytek non-contact IR pyrometer - would have been more accurate.

I used to be a gunsmith, you can keep your Glock™. I carry what goes with
what I am wearing. My 45 won't conceal very well with shorts.

Back in 1973 I used to work for a company that made IR radiometers. I guess the
difference between pyrometers and radiometers is in the eye of the beholder.

As for the emissivity of paints perhaps a single layer sheet of the composite
you intend to build your flying machine with can be used for tests. Paint small
spots with the actual paint you's like to use. Place the sheet out in the sun
and measure the temperature from the reverse side at each spot using your
radiometer. Do this as soon as you place the sheet in the sun. Then again at
each half hour interval there after including cool down times as the sun sets.
This will allow you to plot a rough curve for each colour.


Dan, U. S. Air Force, retired