Ordinary two-millimetre picture glass is cheap and widely available. When carefully cleaned and properly hung it provides excellent presentation and protection for a print. However, care must be taken to avoid reflections from nearby light sources such as lamps and windows. Its polished surface is highly-reflective and under some conditions a print beneath the glass may be completely obscured from view. The best advice is, where possible, to try a glassed print in the relevant display location before committing to a choice of glass.
Various other types of glass are also available. Non-reflective glass has a finely etched surface which significantly reduces reflections but blurs the photograph beneath. This is arguably more noticeable with a glossy print than with one printed on mat or art paper, or other textured material. Non-reflective glass is more expensive than standard picture glass but can be worth the extra cost in some circumstances.
UV-blocking glass provides protection from the ultraviolet rays which cause the most damage to coloured dyes in photographic prints. Long-term fading is much reduced by using such glass, but once again the cost is higher than for standard glass types.
Some manufacturers also make glass which is not only UV-blocking but also, under normal viewing conditions, completely invisible. However, it is very expensive! This so-called invisible glass is quite different from the more common non-reflective glass.
Properly mounted and framed photographs can be expected to have a life as long as 80 years. However, this is dependent in the first instance upon the paper on which the print is made, the type of print, the quality of the inks where this is relevant. A long life is also helped by avoiding locations where:
- extremes of temperature may be experiences, for example above radiators;
- direct sunlight may subject a photograph to excessive UV rays and accelerate fading; and
- damp or moist conditions encourages fungi, rippling and adherence to glass.