The sight glass that indicates boiler water level has always been hard to read. It occurred to me if there was something reflective behind the glass tube it would be easier to read. So I decided, as a trial, to cut a small piece of white printer paper about 1/2 inch by approx 2 1/2 inches and slip it between the metal housing and the glass tube. Reading the water level is now much easier - - and it was very easy to do. I will be watching to see if paper remains dry or otherwise has issues. Just thought I would pass along. Here are two photos to illustrate the above:

If you paint a thin red line on the paper , the line will look thin above the water , but under the waterline it will be magnified
It will completely fill the slot in the protection ,,VERY easy to see

Pavoni Sight Glass Coversion