This is a good reference on selection of white acrylic sheets from eplastics.com
(http://www.eplastics.com/ACRY75080-187PM24X96 )
There are 3 whites in the WHITE color line:
2447 - a lighting white
7328 - a sign white for illuminated signs
7508 - an opaque white for signage.
In the white colors, light transmission changes with the
thickness of the material. The thicker the white material, the less the light
transmission. This is also true in all translucent acrylic sheets (i.e. sign
colors). All transparent shades of acrylic (i.e. bronze, gray, etc.) remain the
same color and light transmittance regardless of thickness.
Reference chart:
0.125" 2447 white - 50% light transmittance - typically
used in overhead lights, xray chart readers
0.125" 7328 white - 31% light transmittance
0.125" 7508 white - 09% light transmittance
0.187" 2447 white - 42% light transmittance
0.187" 7328 white - 23% light transmittance
0.187" 7508 white - 06% light transmittance
0.250" 2447 white - 35% light transmittance - typically
used for photog light tables
0.250" 7328 white - 17% light transmittance
0.250" 7508 white - 4% light transmittance
0.375" 2447 white - 27% light transmittance
0.500" 2447 white - 19% light transmittance.