When framing anything using glass or acrylic as the glazing, there should be an air gap of at least 1/8” between the art or object being framed and the inside surface of the glass. This is to prevent moisture, from the condensation that will almost certainly occur, from transferring to the framed item. A common way to accomplish this is to use two layers of matting between the glass and the artwork. Other ways include special plastic spacers or to use a secondary rabbet in the frame to support the artwork away from the glass.
When cleaning the outside of the glazing, NEVER SPRAY THE GLAZING AND NEVER USE A PRODUCT CONTAINING AMMONIA. Instead, spray a micro-fiber or soft cotton cloth with a 50-50 mixture of distilled water and rubbing alcohol, then use the cloth to wipe the glazing. Spraying the glazing can cause tiny amounts of moisture to enter the frame, potentially setting up conditions for mold to occur. Ammonia is alkaline and can cause damage to the framing contents.
-- Always do the Right Thing the Right Way the First Time - if you can figure out what that is! Ken, Spring Branch, TX