This post will talk about a boring subject - glazing. Which mostly means glass, but is often used a a general term for various materials that protect the artwork such as acrylic (aka plexiglas), styrene, and some newer products coming on to the market. So there is more to it than meets the eye (no pun...)
In framing we use a type of clear flat glass known a plate or float glass. This is usually 2.5 mm thick and also known as single strength. There are various quality levels, but in our shop we use glass exclusively produced for the picture faming business, which has additional properties such as ultraviolet blockers, and different types of reflection mitigators, in addition to being clearer and more distortion free than other types used for windows and the like.
There are a few types of non-glare glass, and anti reflective glass, and they are not the same product. Non glare glass is produced by etching one or both sides of the glass with acid causing a microscopic pattern on the surface which breaks up the reflected light. However it has a frosty appearance and distorts the art image when mats are added. Therefor it is not often used these days.
Conservation glass is clear glass that offers protection from U.V. light. There is an alternative called Museum Glass or Art Glass which both blocks U.V. light, reduces overall reflection without frostiness and offers a high amount of light transmission to view the art because it is not etched, but processed with chemicals.. As opposed to non-glare, this type of glass is known as anti-reflective.
Museum Glass is costlier than regular clear glass and conservation glass, but from both an appearance and preservation standpoint it is worth the money. It is also a bit more difficult to clean. Use a microfiber cloth and non ammoniated glass cleaner on the cloth
In terms of acrylic sheets, it comes in regular (looks like float glass), U.V. blocking (looks like conservation glass) and a product called Optium Museum Plexi that looks just like Museum Glass. It is static free and has an anti-scratch coating that will stand up to steel wool abrasion. You will want to use acrylic on larger pieces (anything over 32" X 40" in our shop), and for very valuable pieces the Optium Museum Plexi option is the best. it comes in 3 mm, 4.5 mm and 6 mm thicknesses.
More to talk about here in future posts, but this is enough for a basic understanding. If you have any questions, don't hesitate to call us.