Whether you use plexiglass or glass as your glazing option you should always use either a mat or spacers to keep the surface of the art off the surface of the glazing. There must be an airspace between the art and the protective glazing. If there is not, then you could experience any number of problems including abrasion, condensation resulting in mold or actual physical attachment of the artwork to the glass or plexi.

Condensation is less of a problem with acrylic plexi than with glass. If the original artwork is pastel or charcoal then glass is preferable unless you use an antistatic acrylic plexi.

Actually, a good grade of acrylic plexiglass is usually superior to glass because there is less danger of physical trauma should the glass break. Plexi doesn’t shatter.

Whichever glazing you use be sure that it is optically coated to screen out the most harmful UV rays to help prevent fading and material degeneration.

I thought plexiglass, being plastic, dosn’t protect against UV rays like glass does?

Correct me if Im wrong!

Plexiglas is a name brand of acrylic glazing. Other manufacturers such as Tru Vue (the brand I use in my frame shop) make versions of acrylic with a UV protector imbedded in the acrylic and not as a coating like glass has to have. It is very difficult to glaze pastel or charcoal with acrylic because of the static. There are more expensive versions with less static and you must choose those when framing that type of art. Other than the UV issue though, Plexi will not harm your painting as long as it isn’t actually touching the art. If it is, then that is another story and I recommend taking it off right away.