Martin Eastburn fired this volley in
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A rug would be good, but grabs dirt.


....not as likely to, upside-down over the top of the thing.

But any _really_flat_black surface ought to work. "Just black paint"
might not... even some of the 'flats' are kind of glossy. But something
sooty black will likely work quite well... unless it ends up heating to
the point of re-radiating that IR!

In that case, a heat-conductive underlayment is called for, to move the
warmth away from the hot-spot. I'd be tempted to try a heavily-sooted
sheet of aluminum. It'll never be touched up there.

Black velvet might work, too.

Lloyd