Hi Dorothy,
When I manufacture them, I used diluted Dawn Dishwashing liquid hot water and a scotch brite page, the pad will not scratch the surface, the Dawn will cut any grease and the hot water will also help with any embedded oils and dirt, make sure you screen is at room temp or above and douse with the diluted dishwashing liquid, rub fully with the scotch brite then rinse in water again and dry with a clean lint free towel, let it dry for about 15 minutes and then hold up to light to see if you have removed all of the contaminents, I don't recommend general spray on cleaners as they sometime will have minute amounts of oil in them that can embedd in the glass, the only wipes I recommend is the windex pouch wipes, I use these in the field for finger prints, and then clean when back in the shop to remove any residue.
Dave Parker
Satin Snow Ground Glass
PS. To everybody, I recommend doing this procedure about every six months, not only does it clean the glass, it will infuse a small amount of moisture into the screen, which can help keep it from becomming brittle..
NOW do NOT use this procedure for fresnels or enhanced screens such at Betties, Maxwells, Etc. as you can scratch them.