The three basic categories of glass for picture frames are clear glass, reduced reflection or non-glare glass, and anti-reflective glass. Each type of glass has a different appearance and can affect the photo or painting contained within in different ways. All three types of glass can be UV-protected to preserve the artwork or photos in the frame. Acrylic glass is also available, though this is not true glass and it can affect the way the picture is presented. Glass intended for use in picture frames can be cut to size for any frame, and custom glass can be cut, usually at a higher price than pre-cut pieces.
Clear glass for picture frames is lower quality glass that is not treated in any way, except for a possibly UV protectant. This is the least expensive option for picture framing glass, and it is just as durable as any other type of glass. The main difference between clear glass and other types of glass for picture frames is the amount of glare that will be present when light hits the frame. Clear glass is likely to produce a significant amount of glare when light shines directly on the picture, meaning it may be difficult to see the picture beneath. If the clear glass is coated with a UV protectant, it can still keep UV rays from damaging the picture beneath.
Reduced reflection or non-glare glass for picture frames reduces or eliminates glare altogether, meaning one will be able to see the picture within the frame clearly in all conditions. Many artists and galleries choose this type of glass to prevent glare from blocking the image in any way during showings in galleries or museums; lights are very often mounted directly above the hanging pictures, meaning glare can be an issue. This type of glass costs more than clear glass.
Anti-reflective glass, sometimes known as museum glass, is also a glare-resistant glass, but it also reduces any reflections that may be seen in the glass. This creates an almost perfectly clear glass that does not interfere in any way with viewing of the picture within the frame. Of the three types of glass available, this is the most expensive by far. It, too, can be UV-protected to prevent the picture within the frame from being damaged over time by UV rays. Museums and other establishments that want superior protection and display will choose this type of glass over other offerings.