So, you have artwork, or a diploma, a photo or a document that you want to frame and protect from airborne pollutants. The type of "glazing" you choose for your picture frame glass will depend on your budget, the items you are framing, and where you are hanging your pieces. Do you want a glossy shine
so that something in the art stands out? Or maybe you’ll choose one that doesn't easily reflect light for a more muted look.
There are a number of options. The most common glazing is regular picture glass, but there is also non-glare glass, conservation glazing, museum glass, and acrylic glazing.
"Glazing" refers to the coating on picture frame glass or acrylic (Plexiglas) used in framing, and the protection they provide to the contents.
One should keep in mind the significance of the location of the frame relative to any natural or strong light sources or windows in determining which type of glass to use. If you want to keep the color of your art from fading, U.V. glass is essential.
Regular Picture Glass is strong, not easily scratched, and by far the most popular and inexpensive option. It protects the art fairly well, and even has some UV protection. Regular glass is also easy to clean.
That being said, regular glass remains somewhat brittle and it is heavy (compared to acrylic glazing, according to the book, Mat, mount, and frame it yourself By M. David Logan.)
For artwork hanging in front of a window, you may want non-glare glass which is finished to diffuse reflected light. This gives the glass surface a matte finish, says Tru Vue.
A disadvantage to non-glare glass, which was noted online in Estrella Fine Art, Glass in Picture Framing 101, is that it’s best to view the framed artwork from directly in front of it. This type of glass distorts the view of artwork when viewed from any angle, especially because of reflected light.
Conservation glazing filters out more than 97% of harmful U.V. rays. Because of the glazing, your artwork is significantly protected from “pollutants,” according to ehow.com. It is expensive, but it reduces possible damage to your artwork.
The best glass available which you would use for pieces of the highest value is museum glass. According to Wikipedia, some glazings, including Museum glass, have a coating which makes the glass practically invisible under ideal lighting conditions.
There could be a slightly green-colored tint to it, but apparently, these tints seem to disappear when placed in the frame. With its U.V. protection and its clearness, museum glass is the ultimate glazing, according to ehow.com.
Another popular type of “glass” which comes 2nd behind regular picture glass is acrylic glazing, commonly called 'Plexiglas'> (actually a brand name). Reasons why acrylic glazing is so popular, according to ehow.com, are that it’s much lighter than glass, it’s very difficult to break, it blocks 99% of the damaging UV, and it’s available in both regular and non-glare forms.
Disadvantages of acrylic glazing are that it scratches easily, and it is expensive because it is considered “higher quality” than regular glass. Also, because it is made of plastic, regular glass cleaners will make the surface foggy, and even a paper towel will easily scratch this surface. A soft cloth and a special cleaner are needed for acrylic glazing.
For “loose media” such as charcoal or pastel, Plexiglass may not be the best choice since it could build up a static charge which will attract the pigment particles off the paper. Using real glass helps to prevent this.
Another important point about the glass used in picture framing is that it is necessary to create air space between the glazing and the art itself, which is the main reason for choosing a mat or spacer bars to separate the art from the glazing itself.
“If the paper (or other media) were to touch the glass directly, any condensation inside the glass would absorb directly into the art, having no room to evaporate,” explained Wikipedia. This could cause the art to stick “to the glass, mildew, and other ill effects.”
Of the choices available in protecting framed items, the products that are available help reduce the amount of fading, but no product will eliminate fading. As we have seen, each type of glass has its pluses as well as its minuses.
“Cost, percentage of protection, ease of use, scratch resistance, glare control, and cleaning are all important considerations.”