Abstract: An analysis method for the effect of change in behavior of basalt fiber-reinforced plastic specimens in initial state and after residence in a climatic chamber at 60 ºС and 100 % humidity for 1 month by comparing micrographs of specimen surfaces is suggested herein. This technique involves digital processing of surface micrographs in Anaconda3 software package and rendering them into a grey-shade distribution histogram. Surface micrographs of specimens before and after weathering at 100, 500, 1000, 2000 and 3000 zooms were processed. The difference between the states (initial state and after ageing) was evaluated by comparing the cumulative distribution function. The greatest difference in surfaces of the specimens was observed when processing the micrographs at 500, 1000 and 2000 zooms. A major change in the surface of specimens was observed after 1-month exposure and a minor change was noticed in two months.