We had already written a few posts on the subject of light fading art but recently we came across an old and rather interesting article. After reading it, we deemed it as being far more detailed and better researched than we had already written, even though our posts are based on our experiences and empirical observations over the years. This article, reproduced below, had all the headers cut and was pasted in an old school project book. Although we'd like to attribute it to its original writer, we can't, as all the authoring information was removed. Nevertheless, if someone does know, please email us. In the meanwhile, here's the article: Darkness is the enemy of visual pleasures while its nemesis, light, is its friend and ally. Without light we could not behold all which satisfies our eyes and ... enriches our lives. A beautiful child, a colourful flower, a delicate watercolour, none of these could be viewed or appreciated in the absence of light. But light, while pleasing our visual sense, can also be the enemy and destroyer of that which is so beautiful and pleasing. Why is this so? it is because, light, when concomitant and adjunct to humidity and ambient air, can and does cause and begin fading, discolouration, and embrittlement to a wide range of materials commonly used in art including paper, fabrics, parchment, leather, fur, wood, resins, gums, glues, dyes and plastics. This damage is serious and irreversible: No conservation treatment can restore color or strength to light-damaged materials. But careful framing and display can minimize the damage. When framing works of art, it is important to remember: 1. Damage from light is cumulative and irreversible. 2. The rate and amount of damage depends on both the quantity and quality of the light falling on the artwork. 3. Luckily, most deterioration from light can be attributed to the U.V. portion of the spectrum, which is invisible and doesn't help us see colours, so it can easily be removed by incorporating a filtering material in the framing. 4. But one must also limit the amount of light an object receives while on display to significantly extend the useful life of objects. Fugitive materials like watercolours and textiles should never be exposed to sunlight, even with U.V. filtering glazing. 5. Ultra-violet filtering glazing is only one important part of conservation framing which can help protect sensitive art works from the effects of light. Conservation or museum quality matting materials used with proper hinging and framing techniques are also essential for the long-term preservation of framed object. INSTABILITY OF MATERIALS OF ART Although the materials of art were always susceptible to damage by light, the combination of traditional painting "Art ounce of prevention in cautious framing and display is worth considerably more than a pound of cure.. since the prevention is relatively easy and the cure simply does not exist." techniques and the use of more inherently stable materials made early painting relatively more resistant to fading. In the 19th century, however, an explosion of technological development spilled into the plastic arts through the introduction of clear, vivid new pigments based on coal-tar derivatives and aniline dyes. These colorants soon became notorious for their sensitivity to light, and science was called on to protect what it had made. As early as 1886, the British Government responded to public criticism that watercolours were so fragile as to be uncollectible, by commissioning a study to investigate their imperma-nence. Prepared by a chemist and an artist, the Russell and Abney Report on the Effect of Light on the Fading of Water Colour was issued in 1888, and in a practical fashion studied the fading of various popular pigments under different circumstances of exhibition. Their report identified the most damaging light sources and suggested a change from daylight to low artificial light levels for museum display to reduce the risk of fading. They also reported that artists could use a relatively more permanent palette for water color by selectively employing mineral pigments and shunning the most fugitive colours. Later historical documents, such as the Burlington Fine Arts Club's Report on Methods Devised for the Preservation of Drawings in Water Colour (1894-98) added to the Russell and Abney Report by suggesting that the deterioration of some light sensitive colours could be slowed by removing moisture from the micro-climate of watercolours within the framing. This innovative notion, accepting as it did the fact that collectors cannot control artistic impulse, concentrated on the measures individuals could take to preserve art objects in their control. Further studies have shown that limiting light in the micro-environment is the best, most practical alteration we can make for the preservation of works of art. CHEMISTRY OF LIGHT DAMAGE Most of the light energy around us is converted to heat, but the minute fraction of light which is absorbed by materials is responsible for initiating much surface degradation. 2 The organic materials which make up art objects are primarily composed of carbon, oxygen, and hydrogen atoms bonded in an enormous variety of ways. The direct breaking of each of the possible bonds, called photolysis, requires a specific blast of energy. This "activation energy" can be supplied by individual photons of high energy light. The broken bonds and certain bonds "activated" by heat and light result in the formation of "free radicals" which, in the presence of moisture and oxygen, start a chain reaction of photochemical damage attacking other molecules in the material. In theory, such chain reaction once started would soon completely destroy a material, but luckily, the process is not particularly efficient since the free radicals also attack each other. And, depending upon the particular material, and in the presence of conditions favourable to preservation, such a reaction may take years to begin, and proceed so subtly as to be unnoticed unless compared to a protected sample. Unfortunately, the protected sample which proves the damage is too often a portion of the art object itself; a recently unframed water color by Winslow Home (1836-1910) described by the owner as a "Sloop in Fog Off Gloucester", showed bright bands of orange and purple-red magenta around the edges of the sheet which had been protected from light by the mat. This sloop, now floating in a grey-blue fog, started its life in a vibrant sunset. Although loss of color is frequently the most dramatic damage attributed to light, it is not the only adverse phenomena we have to worry about. Paper fibres and the sizings, dyes, brighteners and tillers sheets contain may yellow or bleach with light. Pigments in paints and coloreds inks used in printmaking of all types many not only fade, some colours darken to black in light. Drawing and writing inks often can be lost if left on prolonged display, while wood and wood products darken considerably in exposures of short duration. Needlework and fibre arts, and leather pieces are susceptible to fading, embrittlement, tendering and powdering. Photographs, even if properly processed, may yellow and show stains or the surfacing of silver deposits. The rate at which this inevitable damage occurs depends upon the quality and quantity of the light reaching the object. DAMAGE vs. WAVELENGTH Both visible and invisible radiation are found in the electromagnetic spectrum sandwiched between x-rays and infrared rays (heat). Individual photons of light behave like particles, but they also behave like waves which can be described numerically by their frequency or wavelengths rather than their color. Starting across the spectrum, at the low wavelengths, higher energy end we find Ultraviolet (UV) radiation at about 200 to 400 nano meters, then visible blue to red light from 400 to about 700 nano meters, and above that, infrared (IR). Physical chemists have determined that wavelengths shorter than 500 nano meters do not penetrate the earth's atmosphere, so it is only the light between about 300 and 500 nano meters, light from the blue and blue-violet and primarily the near UV range which is powerful enough to induce photochemical damage to organic materials. REDUCING DAMAGE IN THE VISIBLE RANGE A practical rule in physics, called the principle of reciprocity, states that the net photochemical damage is the result of the total exposure an object receives. The damage is cumulative, so illumination is measured in units which account for both the intensity and duration of Diagram #2 — Control of Light exposure, such as "foot-candle-hours". Illumination at 100 foot-candles for 10 hours is expected to do as much damage as illumination at 10 foot-candles for 100 hours.' (A foot-candle is the amount of light a standard candle will cast on a one-foot square held at a distance of one foot.) Museums have set admirable standards in an effort to prolong the life of their collectives. Many now require that their most light sensitive objects (prints, photographs, drawings, watercolours and textiles) be displayed at no more than 5 foot-candles of illumination for periods of no more than 10 to 12 weeks a year. Paintings and wooden objects may be displayed for longer periods at 15 to 20 foot-candles. This effectively reduces the exposure of works on paper to about 16,000 foot-candle-hours/year, which at higher exposures, say on a sunny wall in a private home, the object might receive in just a few days. Because the human eye is able to adjust to light levels over several orders of magnitude, the prescribed lighting is monitored with handheld light meters, and adjusted with screens and filters at the fixtures. For home use, the best advice is to illuminate art at the lowest possible level practical for viewing. The human eye, described as "a camera plus a computer", is perfectly able to see colours at very low light levels if attention is paid to ambient lighting design, especially to eliminate glare and "hot spots" within the room. The damage caused by breaking bonds on a molecular level is cumulative and irreversible. "Dark" storage does not rest or repair light damage. In fact, some further darkening of wood pulp containing papers has been documented even after the sheets have been removed from exposure." Remedial conservation treatment can reverse the damage which can be horribly disfiguring to a work of art. Collectors are to be encouraged to follow the museum's example in limiting light levels. REDUCING DAMAGE FROM U.V. Low light levels are not enough to ensure the stability of materials, however. Damage is done to organic materials even by traces of radiation in the U.V. and light in the blue-violet portion of the spectrum. All these damaging rays are present in abundance in sunlight; artificial light sources vary in their emittance, but in general fluorescent tubes emit light rich in middle and near U.V, while incandescent (tungsten) bulbs contain only about 4% of their light in the U.V, range. Since U.V. radiation is invisible to the human eye, it has no effect on our color perception (except in modern fluorescent or "day glo" colours) and can be removed from the illumination falling on art objects without diminishing our enjoyment of them. But, by the same logic, the also damaging blue and blue-violet rays which are necessary for humans to see reds cannot be removed. It is another unpleasant fact of life that the very act of seeing a work of art in all its colours is dangerous for it — all display causes damage. A couple of studies have tried to compare the damage caused by equal illumination in daylight and artificial light. One study showed light from an overcast sky filtered through window glass caused five times as much damage as the same amount of light from an incandescent (tungsten) lamp. Another calculation compared daylight with (he U.V removed to illumination from tungsten lamps, and found the filtered daylight to be three times more damaging. The sun and fluorescent tubes are dangerous light sources for works of art, and their emissions should be modified when used. Filtering male-rials in the form of plastic or glass sheets and varnishes have been developed to protect works of an by absorbing the most damaging portions of light. Museums and galleries control all the light entering their exhibition spaces by filtering and blocking off skylights and windows, and by filtering lamps in the exhibition areas. For home use, low light levels in the form of drawn drapes or cloth drapes over the frames of sensitive objects and filtration of U.V. light at the frame gives the best results. EFFECTIVENESS OF FILTERING MATERIALS Theoretically, a perfect filter for framing art would pass all visible light, but no invisible U.V Efficiency of filtering is the most important consideration in choosing a particular filter for framing. The material should remain effective in filtering for a prolonged period to justify the added expense of the filtering material over the cost of ordinary glass. A material which is less reflective allows a better effect in lighting at low levels since it diminishes the problem of "hot spots" in the lamping. Ease of use, and resistance to scratching are also important considerations. A filter which is non electrostatic would increase its usefulness in protecting friable media, such as heavy pencil, charcoal or pastel drawings (which can NEVER be safely framed under a plastic or acrylic sheet due to the development of static when cleaned.) For a number of years, Rhom and Haas, Cryo Industries, and General Electric have offered U.V. filtering glazing products to framers. Their products are either plastics made of acrylic or polycarbonate incorporating U.V. absorbing resins in the sheets, or layers of U.V. filtering materials laminated to the surface of glass. Although light weight, the plastics tend to scratch and build up static within the frame with cleaning, and the laminated glass products have been expensive, hard to obtain and they are brittle and difficult to cut to custom sizes. Recently several new U.V. filtering standard thickness glass products have been introduced by Tru Vue, called Conservation Series and Museum Glass. Conservation Series U.V. filtering glass is available in clear and reflection control versions. Museum Glass is an optically-coated reflect ion-free product which is designed to increase the transmission of light through the glass. In addition, both products can be cleaned and cut with little more effort than ordinary glass. This new line of Tru Vue products has excited the interest of museum professionals since these offer the practical possibility of U.V. filtration without the disadvantage of static build up within the frame. When should a collector be encourage to use one of these materials in a frame? Any work of art possessing color should be assumed to be light sensitive, and would therefore benefit from having U.V. filtration in the frame. In addition, photographs, textiles and modern cream coloreds papers are all sensitive to exposure to U.V. The collector must be reminded that this filtering does not eliminate the need for low light levels an avoidance of exposure to sunlight. Some very few exceedingly fugitive pigments seen in watercolours, Japanese prints 19th Century photographs and some textile dyes need to be especially guarded from all light. Other pigments used in these works, and the paper or fibre supports of these objects will certainly benefit from the filtration. Any structural or even cosmetic change must be lamented as it removes an object from the intent and design of the artist. Although any particular object may retain aesthetic significance, or accrue new significance despite unintended changes, it loses some of the magic once possessed as a deliberate achievement by a remarkable human being, our obligation to the artist isn't sufficiently convincing, one might also consider the difference in market value for similar objects in differing conditions. Responsible and cautious owners with frame sensitive artworks must source ultraviolet filtering materials, to slow the effects of exposure to light — fading, embrittlement and discolouration — and the light of all types falling on the framed artworks by lowering blind using incandescent lighting and keeping daylight and fluorescent fight away from the objects of art. Additional help and information on the advantages, disadvantages and the qualities of glass and other picture framing glazing materials click to our Picture Framing Glass page.