Conservation Glazing for Fine Art

Glazing Basics

The glazing, which can be either glass or plastic (such as acrylic or polycarbonate), is the clear sheet over the face of works of art on paper that provides protection from dust, pollution, and other environmental factors and that also filters out some of the harmful UV light. Glazing can be treated or coated with a variety of substances to more fully block damaging UV energy as well as to reduce reflections from its surface, making it easier to view the art as the artist intended.

It is very important that any work of art on paper have sufficient space between the glazing and the artwork to allow for air circulation, and the natural expansion and contraction that paper goes through with changes in temperature and humidity. In most frame designs, the mat board provides this insulating material, but when a mat is not used for design aesthetics a spacer can be placed in the rebate to lift the glazing away from the art. Certain types of art require more space to be safe from damage, such as pastels and charcoals that should have at least 5-6 mm clearance from the glazing.

When dealing with conservation of antique and historic framed artwork, retaining the original historic glass should be a priority if appropriate and possible. In these cases, other measures must be taken to protect the artwork from damaging UV rays while preserving the antique glazing.


UV Damage and its Effects on Paper Artwork

It is important to note that all forms of lighting that artwork can be exposed to can cause some level of fading and damage to both the paper and the pigment on the paper. It is not direct natural sunlight only that damages art and photography. Ultraviolet rays may be the quickest and most severely harmful source of light damage, but it is not the only one. Fluorescent, tungsten and other light sources, visible and invisible to the naked eye have some harmful characteristics. For this reason, it is important to not only reduce the exposure to UV rays, but also to closely manage the overall exposure to all light sources carefully for especially valuable and fragile artwork.

Each type of light (tungsten, fluorescent, and sunlight) contains different amounts of UV energy. Sunlight contains the highest UV levels and is the most damaging, followed by fluorescent. Tungsten carries very little UV energy. UV energy can damage photos by fading the image as well as yellowing and/or embrittling the paper. One of the ways it fades photos is by breaking the internal chemical bonds of the color molecules that form the image. This causes the molecules to become colorless and invisible to our eyes. The more this happens, the more the image fades. This process is called photolysis.

Another way that UV energy fades artwork is by photo-oxidation. UV energy excites the color molecules, making them more sensitive to oxidation (the same process that causes iron to rust). This is a two-step process (excitation-oxidation) that won?t take place without both UV energy and an oxidizing agent. Unfortunately, our air is full of oxidizing agents, most notably ozone. Both photolysis and photo-oxidation can cause photographic prints and artwork to yellow or become brittle over time.

Tungsten lighting emits fairly low levels of UV. Because of this, many people mistakenly believe that, since they light their homes with tungsten bulbs, they don?t have to buy UV-blocking glazing for their frames. However, research by a major manufacturer of photographic prints has shown that the dominant type of light in homes is still sunlight through window glass. This means that the photos we display are actually being subjected to the harshest of type of light and therefore really do need protection.


Conservation Glazing Materials

Both glass and plastic glazing are available for frames. Glass has the advantage of being resistant to scratching, but it is heavy and fragile. Very large photos should be framed with plastic glazing, as plastics are lighter and less prone to breakage. Plastic, however, is more easily scratched. Both glass and plastic glazing are available with special coatings to reduce glare and block UV.

As you would expect, one of the most important qualities to look for in glazing is UV blocking. The UV energy is absorbed at the surface of UV-blocking glass and is thus prevented from reaching and damaging the artwork. To be considered conservation grade, glazing must block at least 97% of UV energy. Never glaze valuable fine art with anything less than 97% UV protected glazings.

Additionally, it is recommended that the glazing pass the photographic activity test. Other qualities to look for are anti-reflection coatings, color-neutral or color-enhancing coatings, and scratch resistance. Anti-reflection coatings disperse the light that strikes the glazing, thus reducing reflections from light sources such as indoor lights or windows. Some glazing manufacturers add colorants to their coatings to make the glazing appear more neutral in color. This is because framing glass naturally has a slightly green tint, which can affect the color of the art behind it. Finally, some glazing is treated to resist scratching. This is really important for plastic glazing, as it is more susceptible to scratching during handling.

An art and design expert at any of our FrameStore locations can personally advise you on making the right glazing choice.

Museum level framing must use at least 97% UV filtered glazing materials, and for optimal presentation, Museum Glass with 99% UV protection and 98% anti-glare properties allows for the best and truest color transmission. This allows the artwork to be conserved at the highest level possible while showing the artwork as it was intended by the artist.


Tru Vue Museum Glass 99% UV Blocking


Talk to an art and design expert at any of our nine southern California custom-framing stores for more information on conserving and protecting your fine art.

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