This doesn't have to do with PJ screens, but it does have to do with reflecting light off a surface.
One of my other hobbies is photography. A DIY project that I have in progress is to build a DIY beauty dish. For reference, this is a beauty dish:
Basically it is a big bowl with the flash in the middle.
The desire is to find a white paint mixture for the interior surface that maximizes the gain, with minimal to no hotspotting and gives zero color cast.
Most people that DIY a beauty dish just hit it with a couple of coats of flat white spraypaint, but I was wondering if improved performance might be found in using a mixture that maximized light reflection and dispersion without moving to a fully silver/polished/reflective dish that gives a light quality I am not looking for.