I tried to determine the CR particle size by diluting 1:100 in IPA, but the particles seem to agglomerate. My understanding is that a particle size smaller than the wavelength of the laser is needed, otherwise the particles act as a photoblocker.
Initial particle size was 700 nm, after 1,5 h I found 3000 nm. I guess the primary particles as dispersed in resin are smaller.
It is a real problem that particle size can not be determined while dispersed in resin only. Any diluent might change particle size.