When framing your art, two main things need to be considered; the medium used to create the art, and the surface it was created on.
● Pastel artwork
Pastel artwork should always be framed behind glass. Acrylic is not preferable as it can have a static charge to draw any loose pastel dust onto it. A mat or spacers should be used to ensure the painting doesn't touch the glass.
●Acrylic artwork
Acrylic artwork painted on canvas does not need to be placed behind glass. However, if the painting is done on paper, then I do recommend framing behind glass or plexiglass as an extra layer of protection.
●Oil artwork
Oil paintings on canvas typically are not framed behind glass.
●Art created with watercolor or colored pencil on paper
To protect from moisture oils, dirt, and dust, it is recommended that these artworks be framed behind glass or plexiglass. Using a mat around the painting is a personal choice.
I hope you find thus informative and helpful.
Kelly