'Reflectivity' is a widely employed technique for surface characterization. 
It is known that smoother surface reflects more as compared to the rougher.

We have carried out surface reflectance measurements to identify the smooth 
and rough surfaces on samples of all types of glasses that are being used 
for RPC fabrication in our laboratory.

Reflectance from a circular region (of about 6 mm diamater) was recorded 
from both surfaces of all samples, as a function of the incident wavelength 
(visible region). These measurements are shown in the graphs below. It must 
be noted that all the measurements in our experiment are only 'relative', 
and by no means absolute. 

All measurements have been thoroughly checked for reproducibility, and this 
enabled us to unambiguously identify the rough and smooth surfaces.