The Importance of Selecting A Quality Glass
There are many decisions to make when framing artwork. Just as there are many types of mats, there are many types of glass. The more you know about conservation and the environmental hazards which threaten your artwork, the better you will be able to protect it.
Glass protects artwork from environmental hazards: Light, pollutants, pests, moisture. These all conspire to damage your art but glazing can alleviate or even eliminate some of these hazards.
Light can cause brittleness and discolouration of paper and pigments. Ultraviolet radiation (which we know as UV light) is the invisible short wave component of light which is most destructive to paper. UV strikes art surfaces directly or by reflection. Its major sources are natural daylight and fluorescent lighting.
Why is it damaging? Papers containing lignin, waxes, plasticizers, sulphur, iron or other non-cellulose products will quickly deteriorate with exposure to light. The purest of papers and pigments can still bleach or discolour with exposure to light.
How can you prevent this? To avoid damage from light, try to hang artworks out of direct sunlight or fluorescent lights.
If this is not possible, it is important to choose the correct glazing with ultra violet filters. Museum grade glass is the highest quality of glass which has an invisible coating on the inside, which blocks about 99% of harmful UV, compared to the approximately 40%-50% blocked by plain glass. UV-filtering glass and acrylics come in various grades of protection from 50-99%. Non-glare, or anti-reflective glass has either a special coating, or has been chemically treated, so that the outer side of the glass scatters the reflected light in a room, giving a softer reflection. Anti-reflective type glazing does not protect artwork and many believe it causes more damage than even plain glass.
As you can’t be sure where your artwork will be hung in the future and what value will be placed on it by your descendants, it is recommended to ere on the side of caution.
Most artworks should be put under glass, as water in the atmosphere can come into direct contact with exposed surfaces causing buckling and warping, and in combination with other air pollutants can provide conditions that allow mould to grow. One of the dangers of moisture, other than just wetting art and ruining the media, is its potential to combine with iron and sulphate ions in the paper or atmosphere, resulting in the formation of sulphuric acid. The acid causes embrittlement and discolouration of papers and other fibres.
NOTE: Oil paintings on canvas are usually not glazed, A greasy film appears on the inside of the glass. Professional cleaning may be needed if an oil is glazed to protect it from a fire place for example.
Air pollutants included dust and mould spores, fibres and chemicals. Airborne grease, smoke particulates and dust cause staining over time on exposed artwork. Smoke and cooking grease can stain paintings or artwork quite quickly and permanently. If left exposed artworks made of natural fibres can also provide a haven for pests and will deteriorate very quickly.
Sealing an artwork off from the surrounding air can prevent most of these problems