Effects of the duration of chemical etching on the transmittance, absorbance and optical band gap width of the CR-39(Polyallyl digly colcarbonate detectors irradiated to high neutron doses (12.7,22.1,36.0 and 43.5 Sv) were studied. The neutrons were produced by bombardment of a thick Be target with 12 MeV protons of different fluences. The unirradiated and neutron-irradiated CR-39 detectors were subjected to a step wise chemical etching at1 h intervals. After each step, the transmission spectra of the detectors were recorded in the range from 200 to 900 nm,and the absorbances and optical band gap widths were determined. The effect of the etching on the light transmittance of unirradiated detectors was in significant, where as it was very significant in the case of the irradiated detectors.The dependence of the optical absorbance on the neutron dose is linear at short etching periods, but exponential at longer ones. The optical band gap narrow swith increasing etching time. It is more significant for the irradiated dosimeters than for the unirradiated ones. The rate of the narrowing of the optical band gap with increasing neutron dose increases with increasing duration of the etching.