I would have thought this to be a fairly simple value to discover, but
after some pretty extensive searches on the internet, I have to admit
I'm coming up empty.

Does anybody here happen to know the density of positive photoresist
solids (novolak)?

I'm curious, because I'm trying to determine the actual efficiency of a
spray coating system.  My specific case:

I am able to spray coat a 100mm wafer with a 5um layer using 230ul of
AZP4620.  AZP4620 is stated as being 41% solids, but I believe this is
on a weight/weight basis. It is a simple enough calculation to determine
the volume of the resist coat (0.039 ml), but I have no direct
correlation between this and the actual amount of resist dispensed. The
only hint I have is that the specific gravity of PGMEA is 0.926, and the
specific gravity of AZP4620 is 1.08.  Unfortunately, I cannot assume
additive densities, since the process of the resin entering solution may
modify the overall density of the system.

Does anybody have any information?

Best Regards,
Chad Brubaker