Glass, or glazing, is a very important element to the frame package, as it is the barrier that protects the visible parts of your artwork. All glass is not created equal, however, and for maximum protection, care must be taken to choose the correct glazing.
UV-filtering glass has an invisible coating on the inside of the glass which blocks about 98% of harmful ultraviolet rays, as compared to the 50% blocked by regular picture glass. Most people, when they hear the term “UV rays,” automatically think of sunlight; however, there are still UV rays present in our indoor lighting as well. As we become more energy conscious, and begin switching over to more fluorescent lighting, this becomes more of a concern, as there is a higher concentration of these harmful rays than in incandescent lighting. UV-filtering glass, however, is not an absolute. Just as you can still get sunburn at the beach, even with sunscreen, art protected by UV-filtering glazing can still fade if hung in direct sunlight or harsh lighting. Care should be taken when hanging the art that its exposure to harsh lighting is minimized.
Non-glare, or anti-reflective, glazing can be an excellent choice when reflections are a concern. Non-glare glass has either a special coating, or has been chemically treated, so that the outer side of the glass softens the reflected light in a room. Depending on the intensity of the light in the room, this softening effect may be more distracting, as the effect can make your art look hazy. In cases such as this, anti-reflective glazing would rectify the issue. A special coating on the outside of the glass reduces the amount of reflected light, which will make the artwork appear brighter and sharper. Of course, UV-filtering should still be considered when using anti-reflective type glazing.
Acrylic glazing, or Plexi-glass, is available for larger works of art, where using glass could be dangerous or overly heavy, or for items that need to be shipped. UV-filtering and anti-reflective acrylics are available as well.
As a rule of thumb, art on paper should always be under glass. Changes in humidity can cause exposed paper to buckle and warp, and airborne grease and dust can cause staining over time. Due to a continuous “out-gassing” by oil paints, paintings on canvas are generally not glazed. Over time, this out-gassing causes a greasy film to appear on the inside of the glass, which would have to be cleaned by a professional framer. Needle art, such as cross-stitch and crewel work, often are not glazed. However, this is usually a personal preference. Most framers will advise the use of glass, which will protect these often very labor-intensive works of art from staining and other damage. Any artwork that receives matting should always be glazed. Just as changes in humidity can cause buckling and damage to art on paper, the same damage can be caused to that carefully chosen mat design if not protected with glazing.