I thought of making a frame before glass door an install very fine sreening .Screen would slow down ash hitting glass an you can still see the fire .Never did it as my Alaska stoker created too much fly dust for the wife . my 2 cents jack
My Alaska came with a screen to protect the glass from fly ash. I never used it until this year when I had to replace the glass. It does help a to keep the fly ash from sand blasting the glass. I clean the screen with my shop vac with a HEPA filter about 1 a week.