o.k., thanks, bill, for that. It's apparently the same with using diffuse colours on objects. multiplying an object's colour by white (1) gives the unmodified colour, but multplying an object's colour by black (0) can only give black as a result. it may just be a bug in my version of P7, but the glass/mirror ball material sets Reflect_Lite_Mult at 1, whereas the metal/chrome material sets Reflect_Lite_Mult at 0, hence the only one that works for me, unmodified (with IBL alone) is the latter.