Glazing is a term framers use to refer to  “the glass”, and glazing products are available as a wide variety of materials designed to address certain criteria such as clarity, ease of cleaning, safety, filtration of ultraviolet light as well as light in general, and reflection control.  Because of the range of products available, sometimes we spend as much time at the design table educating our customers about glazing, as we do choosing frames, mats, and other components.  What follows here is neither fully scientific or comprehensive, but attempts to address some of the most common issues that come up when discussing this important part of the framing package.

Framers use glazing materials which are either glass or plastic.  Regular glass is among the most inexpensive and easiest to clean without damaging the surface, as well as the traditional material of choice for art frames.  However, glass also poses the greatest safety risk to fragile structures and surfaces we find with artworks and ephemera.  Basically, broken glass cuts stuff up.  Safety glasses as well as laminated sheets exists to address this issue to some extent and are quite lovely, but not foolproof while also being heavy and expensive.  Because we are located in a seismically active corner of the world, and because we frame many large scale works as well as works which travel or go in and out of storage, we advocate, in general, using acrylic as part of preservation framing packages.

Glass is available plain or with UV filtering properties;  non-glare (with a finely etched surface to break up reflection);  water white (low iron content with virtually no color);  antireflective (with optical coatings to drastically reduce reflection without sacrificing clarity);  as safety glass; or as laminated sheets to reduce damage if broken.  Acrylic as well has standard and UV filtering grades;  comes in a range of thicknesses (at large sheets, thinner material can bow), and is available in non-glare, abrasion-resistant, and antireflective grades (trade name Optium).

Perhaps the greatest consideration brought up by Sterling’s customers vis-a-vis glazing has to do with UV light.  As an invisible part of the light spectrum, UV light carries the greatest degree of energy, energy which can both break down pigments, dyes, and fibers, as it can accelerate chemical reactions inherent in certain media.  Think:  faded vintage color photographs or even color posters that lose their vibrancy in time.  But for the number of times people come to us saying, “I don’t know how I want to frame it, but I know I need a UV filter because where I am going to hang it, it will get direct sun.”  We use a great deal of UV filtering glazing and in general I think it is a helpful component to preserve the thing inside the frame.  However, UV light is just one component to consider and one should think in terms of energy exposure (the full spectrum of light, temperature and humidity fluctuations—not to mention inherent physical and chemical properties of the artwork or materials in the frame package).  One should NEVER put original artwork in direct sun, and the lower the light, the better.

In fact, UV filtration should never be addressed in isolation as the only issue to address when making a preservation-grade picture frame.  For one, counting on the UV filter to prevent light damage is a little like being a very pale skinned person who lives in northern climes, heading off to Hawaii on vacation in the dead of winter, and using, say, an SPF 20 sunblock on a first long day at the beach.  That person will burn!  However, using common sense, that person would hang out in the shade while dosing themselves for a day or two with intermittent exposure to the sunlight, they’d see much more benefit from their sunblock. UV filtering glazing can be considered this way.  In fact, the primary UV filtering acrylic we use at Sterling comes with paper masking on which is labeled:  Museum Quality Ultraviolet Filtering Acrylic Sheet.  And museum quality UV filtering acrylic?  After years of working in this field, I would wager that it will filter out the UV light it purports to, when the work is hung in museum conditions:  proper number of foot-candles of light indicated for the medium, relatively short periods of exhibition with relative long periods of storage—and with climate control!  A color photograph under a north facing skylight will likely suffer over time, even without any direct light, as will a delicate watercolor made with fugitive pigments.

Granted, few among us live in museums, and we value our light and views as much as we do preserving our artworks, ephemera, and irreplaceable heirlooms.  Conservators suggest to us that UV filtering glazing products should be switched out every 10-15 years, and I tend to trust them a little more than I do the manufacturers who may suggest their products will work for much longer, if not in perpetuity.  Of course, using appropriate materials within the frame package which support preservation of a given medium is paramount.  For really delicate works, even with a UV filter, it’s advisable to leave your shades drawn when you’re not home, or if you are away for extended periods, you might even consider draping such works with black cloth.  It’s a constant struggle to find a balance between preserving our valued artworks and heirlooms, and enjoying our homes, our views, and our light.