IR Absorbing Paint 1

[mprice]

Is it possible to buy paint which absorbs IR light?
I would like to measure the temperature of a small target (1mmx1mm) using an optical pyrometer. The problem is that I will probably end up measurinmg the reflected heat from the the surfaces around the target. It has been suggested that I could paint around the target with a paint that would reduce the IR reflections. Any clues?

Regards
Matt

 

[IRstuff]

Krylon 1602 flat black is the simplest and cheapest solution to reflections.

However, high absorbance means also high emittance. Therefore, a black background will emit a truckload of energy anyway. You need to cool the background. This can be done with either a reflective or absorptive background.

TTFN

FAQ731-376

 

[mprice]

IRstuff,
Thanks for your response.
I intend to cool the back ground with water flowing through a tube near to the surface.

Regards
Matt

 

[IRstuff]

The surface prep is quite important. A rough surface is good, but an ideal surface is one with pyramidal pits, to mimic an ideal blackbody cavity. The paint only gets you to somewhere around 95% emissivity. The cavities can get you past 98% emissivity.

TTFN

FAQ731-376

 

[JStephen]

I remember reading in times past of people testing paint specifically for use in solar collectors. As I recall, the black color of a specific brand wasn't always the one that absorbed the most IR, contrary to what might be expected.

 

[IRstuff]

Krylon's 1602 has been the "poor man's" blackbody paint for over 20 yrs.

TTFN

FAQ731-376

 

[swertel]

You can check out this website for a whole supply of various IR paints.

http://www.intermat.gr/

--Scott

http://wertel.eng.pro

 

[rustbucketguy]

Check the instruction manual that came with the pyrometer. You need to find the spot size ratio information along with the minimum and the maximum distance to the target. When measuring the temperature of the target, the spot must not extend beyond the edge of the target. The black paint on the target should help raise the emissivity and enhance the accuracy of the measurement. If the temperature varies as you move the pyrometer side/side or up/down, then you are most likely incorporating the surrounding temperatures in an average reading. It is entirely possible that the target size may simply be too small to read with your pyrometer.

 

[danw2]

You want the target to be as black and as highly emissive as possible.

You want the adjacent area to contribute as little IR energy as possible, so the poor man's black body black paint is not appropriate for the adjacent area.
I'm not sure how emissive the shiny aluminum spray paint is, but what about surrounding the adjacent area with aluminum foil or something shiny and reflective with very low emissivity?

Dan

 

[davefitz]

another trick when using aluminum (as with lagging) is to specify anodized aluminum- it has an emissivity of 0.95. \although it increases the radiative loss of heat, it also leads to a lower surface metal temp so as to meet OSHA 140 F limit.