So the best way to keep the glass clear is a Powerful Air Curtain inside the cabinet. Before we purchased the one we have now we looked into the nicer cabinets, but I bet price was the decider for the one we got. Another option is multi-layer peel-able sacrificial sheets. These work well, but are expensive and hard to install if your window isn’t the right size. I believe our window is the right size.
Glass vs Plexi / Acryllic:
So I tested this when I had 2 days worth of blasting to do at DMS. I replaced the plexi with a fresh sheet and after 8 hours of blasting, never pointing towards the window, it was pretty well fogged. The next day I replaced the plexi with a piece of glass from Home Depot. After another 8 hours of blasting it was about 50% the fogging of the plastic. But, the cost it so much higher for glass that it just isn’t worth it.
It is more than likely normal use that is fogging the glass. The tell tell signs of mis-use are ice cream cone shaped or swirl shaped deep blasting marks. The consistent fogging is due to normal use.