Quote Originally Posted by efikim
... and I've remembered where I found the reflectances (in a book on building greenhouses).

I remembered it wrong, so my apologies!

white paint reflectance 80-90%
glass mirror 80-90%
polished aluminium 60-70%
aluminium paint 60-70%
stainless steel 55-65%
Thanks for the info, any idea what polished chrome would be?