Isotropic reflector ideas please

[Supersmithy]

Hi there,

If this community doesn't have the answer I'm at a loss

I'm wanting to create an isotropic reflector of infrared light. That is, a metal panel that I can point a thermal imaging camera at and what the camera will see is the reflective temperature of the entire room - be that the camera operator, a radiator on an adjacent wall etc etc.

The 'target' wants to be in the order of 200x200mm in size and importantly we want to produce lots that all behave in the same way i.e. a repeatable process.

Current line of thought is:

3mm polished aluminium sheet to start
CNC blasting using a fairly large grit, glass bead or peaner

The challenge is identifying an approach that can be applied consistently whilst creating fairly deep large indents (curved or flat faces) that are smooth/don't imprint a roughness, retaining the overall reflectiveness....whilst also not deforming the flat plate. A concern about aluminium would also be that it might dull and be less effective with time but SS is perhaps too hard to dent and form? A final finishing process could also be considered.

Any thoughts on process options, suggested grits and beads to try as well as other ideas welcome. And if I could be pointed in the direction of a company that might be able to help with samples, that would be even better!

Many Thanks