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Specifying Lighting by How It Works
Different light sources have different rates of damage for different objects meaning you get different results.
A light source that is harmful to crystalline minerals, semiprecious gemstones and ivory will have negligent impact on old papers, documents, historic maps or boardgames.
A light source that will accelerate fading so aggressively as to embrittle paper can take decades to bleach the fur of a mounted animal specimen and a century to discolor feathers in a headdress.
Even durable objects like fossils and spacecraft can be at risk. Certain light sources will create dirt build-up, gummy films and mechanically attack surfaces.
Put bluntly, the right choice in light fixtures and lamps can protect your collection. The wrong choice can harm and eventually destroy your collection.
You need to pick.
Not the architect.
Certainly not a contractor.
Not even the exhibit builder.
Lighting is too important when it comes to enjoying and protecting valuable collections. Therefore, YOU need to pick your lighting.
Lamps have specific physics. The way the lamp converts electricity into photons determines the damage rates. How the physics works determines the output in energy as photons. Different outputs have different impacts on each specific artifact.
Always look at the spectral output of a light source - the entire and complete spectral output, not just a piece of it - as that output predicts photochemical and photomechanical damage rates.
Lights can be ranked. But first, ALL lights should follow museum practice. They should be lit at the light levels established by the recommended footcandle requirements.
Fade testing ranks light sources from the most damaging to the least harmful. The best light source produces only visible light. Since UV and IR cannot be seen by humans, UV and IR can only cause photochemical and photomechanical damage.
Puzzled about photons? Do not know what light is? Go back to the HOME page and ask “What is light?” next to the button you just clicked. There is also the very popular, white paper “Light and Matter: the Dangerous Romance”.
The least damaging light is without UV and without IR. But the source also has to have a balanced color. Presentation and preservation are connected.
A light source with little blue visible light and 10x the color of red light will turn every color warm. That makes things look older, duller, warmer, darker, softer and fuzzier. But that same imbalance of too little blue light and way too much red light will mismatch blue objects. The visible blue light will accelerate the damage of, for example, a brown, aged paper making the paper appear more gray.
That balance also extends to the mixed-color lights that simulate white light. RGB sources can fool the human eye. But what beauty we actually see is reflected. If the color raggedly exists by overlapping phosphors, like those produced by a LED lamp, colors and details are distorted. Certain colors turn ragged and murky. We loose our ability to see beauty. We are robbed.
Test procedures and results are covered in the published paper titled, “Reflected Energy Matching as a Conservation Tool”.
A famous museum stated Reflected Energy Matching Theory was “the best breakthrough in conservation science in a decade.” But better news is that ranking is applied science that produces results. It is not just theory, but practice. You can protect your artifacts by picking the right lights.
Another important need in a light source is that the best lights should have exacting control. The idea behind the museum recommended footcandle standards that have been used for decades is that footcandle levels must be limited. Objects need to be seen and enjoyed. But light sources with wide spread, stray light and light outside their main beams add to overall light levels which creates visual disability...and exceed recommended light levels.
It is hard to apply the footcandle limits. If the light fixtures spread enough light outside their beams, the artifacts stop being the center of attention. The exhibit gets boring.
Stray light is frustrating. It over lights signs, graphics, walls, floors…robbing the artifacts of their impact. So beam control is vital.
Light spread is why so many museums have walls that look like billboards and put graphics everywhere.
It’s an effort to overcome the lack of control in the lighting. But then the museum wonders why visitors miss the artifacts. And why visitors hurry and do not spend all day.
Humans learn to ignore ad-like graphics and signs at an early age. They automatically filter out the data. So the choice in lighting has surrounded the artifacts in a sea of visual noise. Younger generations especially respond by closing down and ignoring input as their brains automatically “see” advertisements. Good control over footcandles and spread improves learning and, more importantly, enjoyment. Today graphics that are over lit or oversized cause mental shutdown.
Yet there is a third benefit to exacting beam control.
Superb control can also let artifacts of different types of materials with different recommended footcandle requirements be lit side-by-side. A good example is mixing a costume with the jewelry it was designed for and including a pair of fragile silk dance slippers. Or placing an ink set next to a document to establish the age of both artifacts. Or exhibiting a ship’s log with pieces recovered from the ship’s wreck. Superb control helps with interpretation.
On top of telling a better story with related artifacts of different materials lit at different light levels, control lets you direct a visitor’s eyes.
Eyes natural look at what is brightest…even if it is just slightly brighter.
So a case full of a variety of Civil War objects can be lit, so that no visitor misses the single most important artifact as it is lit just a little more brightly. Or a case full of signed baseballs can be designed so that no visitor misses the very valuable Babe Ruth ball at its center. Or a case full of birds, nests, eggs and insects can be lit to assure everyone sees the extinct, rare butterfly mounted into the large diorama.
Or the Ruby Red Slippers can be lit brighter than the dress. The dress is more fragile. But the shoes are the star of the exhibit. By design, the exhibit lights them at the highest recommended footcandle level. Therefore, they are the first thing people see. These shoes literally stop people in their tracks. You can see it on the security cameras. The lighting directs the eyes to what is most important.
Light control can even be the way to point out the all important piece of a massive, historic machine. Or direct eyes inside a race car, so no one misses the dashboard gauges. Or point out a specific famous diary in a case full of books. Good control lets YOU tell the whole story in a more exciting way.
Need more examples? Go back to the HOME page. See the section “YOU CREATE”.
What about visible light? What is the UV and IR content of different lights? What has testing shown?
Click HERE for Excerpts from "Side-by-Side Comparisons of Light Sources" pdf
Click HERE for Fast Facts "How a Tungsten and Halogen Tungsten Lamp Works" pdf
Click HERE for Article "How a Fluorescent Lamp Works" pdf
Click HERE for Article "How a LED and OLED Lamp Works" pdf
Can’t find the complete spectrum of a light source from the lighting industry? You are not alone. Click on the above papers. Full spectrums are provided. Need to know how a certain light works, I mean really works? Get practical, working know-how in these pdfs.
Ranking Light Sources Best to Worst for Artifact Damage
Test results make ranking light sources for their ability to retard or accelerate photochemical damage impossible to debate. This is data that has been peer-reviewed and duplicated by others. Different light sources produce different rates of damage. And remember, condition is a big part of financial value. All rare, fine and valuable objects can be resold. But only those in excellent to good condition get top dollar and break auction records.
Click HERE for Single Sheet of Test Data Watercolor Samples pdf
Correctly used, NoUVIR fiber optic lighting can extend exhibit life further. Testing shows documents can be prolonged 40x longer in exhibit life. See further test data.
CONTENT: Zero UV, zero IR. No UV. No IR.
COLOR: Duplicates sunlight’s visible distribution to within less than 5%, CRI (color rendition index) of 100 (100% of colors identified correctly by real human test subjects), shows the difference between warm whites verses cool whites, warm blacks verse cool blacks, see all cool colors verses warm colors, examples: lemon yellow verses deep cadmium yellow, cadmium red verses crimson, cobalt blue verses Prussian blue, light cadmium green verses viridian green…you get the idea.
CONTROL: Beams have no stray light outside the beam. No haloes. Beams are smooth from edge-to-edge. No dark spots or dim holes. Each beam has a soft, exacting cut-off at edge. No chromatic aberration. No color at the edge of the beam.
COMMENT: It is more than no UV and no IR…NoUVIR®. This lighting was invented and designed from scratch specifically for artifacts and collections. The control is phenomenal. See the “YOU CREATE” button on the home page and explore. What can be done will blow you away.
SCIENCE COMMENT: If you study the blue wool samples, there is still fading. Why? Because these samples are BLUE. The fiber optic lighting has all the visible colors. The blue wool reflects blue. But the blue wool absorbs green, yellow, orange and red. This accounts for 14% of the solar damage.
Note that some of the samples of other types of lighting have not just faded. The wool has turned yellow. It has been oxidized by the light. This part of the wool has lost its structural strength. Photochemical damage is not just fading. It encompasses a whole host of structural changes.
If the fiber optic lighting is perfectly matched in color, the wool looks identical. The green, yellow, orange and red light is no longer present to be absorbed and cause damage. The blue light is almost completely reflected. The matching is not perfect. But the fade rate becomes 1%. One percent! This is over 40 times better than the other light sources. This means monochromatic objects like old papers, books, maps, etc. can greatly benefit.
Click HERE for Excerpts from "Side-by-Side Comparisons of Light Sources" pdf
Why blue wool testing? ISO Blue Wool is the museum and science standard conservators use worldwide to quantify fading and damage caused by light. Long ago the British Navy decided it needed strict fading comparisons. It picked navy uniform material. Each blue sample fades twice the rate. You will find these test strips also placed in cases to monitor fading. Starting with blue wool samples let other conservators and scientists verify the data by duplicating the results with a well-known test strip. NoUVIR and these others have verified test results over and over again during the last two decades by using ISO blue wool as a control for testing.
Check the specification. Check performance. Check the warranty to make certain the fiber is guaranteed to work over an extended period of time.
CONTENT: For plastic fiber systems, zero UV. For pure acrylic systems, zero IR. Other plastic fibers can transmit some IR. For glass fiber systems, possible UV. Some glass systems greatly reduce IR. Some glass systems transmit almost all the IR in the lamp to the fiber’s end.
COLOR: Depends upon the lamp. If the system uses a halogen lamp, the CRI is 100. If the system uses a LED, the CRI is around 70. This means 30% of the colors are misidentified. If the system uses a HID lamp, the CRI may be as high as 80 until the lamp ages dropping the CRI to as low as 55 or worse.
CONTROL: Marginal, unless close to the object. Testing shows scatter, often holes in the beams, striations or uneven beams from edge to edge, grainy beams unless defocused, haloes and poor reach. Most systems cannot light across a room. If there is optics at the end of the fiber, other companies use reflectors and lenses (if any) designed for filament lamps. NoUVIR is the only company offering a fiber optic reflector and a fiber optic lens made specifically for fiber optic optics.
COMMENT: Need more information? See the book excerpts below.
Click HERE for Excerpts from "Side-by-Side Comparisons of Light Sources" pdf
SCIENCE COMMENT: A one-to-one comparison of a competitor’s LED projector using NoUIR aero-space grade fiber and ZDEL eyeballs in the competitor’s system showed the best field performance for the best eyeball to produce 4.6 footcandles. The other eyeballs were dimmer. NoUVIR’s performance with a NoUVIR projector was 36 fc. That means the competitor only produced 13% of the light output of NoUVIR.
Put in another way, the museum needed to install 7 to 8 times the hardware to get the equivalent footcandles. Often the ration is 2x to 4x the hardware with poorer results. Lower cost per unit fiber optic systems are hardly savings if you have to buy, install, operate and maintain twice, three times or more product.
This ratio is not true for effects. When you are making a star field, the stars can have less footcandles and still look beautiful. But NoUVIR has used a single projector for a complete room when other fiber optic star fields need several projectors or illuminators for each sections.
Removing the dichroic filter raised the damage to 53% of solar. The key is not to dim the lamp. Instead, drop the wattage of the lamp. Also always use a quality lamp from a known manufacturer. Less expensive lamps can have poor dichroic coatings.
Testing showed that if the halogen lamp is dimmed to 2900°K, this visibly mismatches the blue in the wool standards. This dramatically increases the IR output of the lamp. The visible footcandle level may have dropped according to the meter.
But dimming a tungsten lamp to half its visible footcandle output only removed 10% of the light energy. The other 40% of the photons shift to pure IR. Testing proves LEDs are a better choice by a large margin compared to DIMMED halogen lamps. The ranking switches. Just remember, an average LED’s output is 75% IR.
CONTENT: 0.5% to 1% UV, 94% to 96% IR
COLOR: All colors present and can be correctly identified, but have a red bias (warmth), CRI of 100, can determine some warm whites verses cool whites and can determine some warm blacks verse cool blacks. A person can correctly sort colors. But the colors have to be fairly distinct. For example, an antique yellow white verses a blue-gray white can be identified. However, a halogen lamp has trouble showing the difference in an artist’s titanium white (warm) verses zinc white (cool) verses lead white (silvery).
CONTROL: Beam control can be sloppy or tight or anything in between depending upon the lamp type and the design of the light fixture. The tungsten filament is easy to aim and focus. These lights usually have no haloes with beams that are mostly smooth from edge-to-edge (a little spotty). Beams do not have a soft cut off at the edge unless they are well designed fixtures or framing projectors. Glare is bad unless the fixture covers the back of the lamp.
COMMENT: For lighting artifacts, do no use open fixtures with exposed bulbs. Look for light fixtures with a deep nose to control glare from the side. Be careful that these lamps do not aim at visitors. Fiber optic lighting has such a tight control, a luminaire will be dark and not blind unless someone stands in the actual beam. This is no true for halogen lights even in well designed light fixtures. Remember, do not create visual disability. You want people’s eyes to see well and for people to be comfortable all day in the space.
SCIENCE COMMENT: Cases lit by halogen lights have to be carefully designed. The IR in these lights encourages a case to breath and ingest daily pollution. Since the infrared heats the artifact’s surface, halogen lights make things dirtier over time and can mechanically fissure them.
Today filtered halogen lights are blacklisted by green groups. But the fact is that for museum applications and collections at home, they can be a far better choice than LEDs or fluorescent lights. Photochemical damage is never green. Of course, our opinion is that if it is valuable, use NoUVIR.
SCIENCE COMMENT: These lamps are good for short term, occasional lighting. Compare the numbers. An LED has to absorb the inefficiency of the whole circuit even though marketing ignores the needs of the consumption of electricity to run that whole system. Each year LED technology gets better.
But an ordinary light bulb takes a lot less in resources to manufacturer. And the wiring (the circuitry) to run it is simple. Therefore, the LED’s energy savings has to offset the LED’s manufacturing. In 2017 halogen lamps had a profit margin of 4%. LED lamps had a profit margin of 40%. Profit margins in LED lamps have dropped, but are still higher adding real incentive to claim LEDs are more “green”. Basic tungsten light bulbs use little materials and energy to manufacture, compact into small volume for disposal and never need updates or have to be replaced because they are obsolete.
Today there is a movement to reverse legislation and again allow the manufacturing of all types of tungsten lamps. The reason is that they are better for the environment in certain applications. If you are lighting a space not used often like a closet, a shed, a storage locker, a garage with windows, a basement, a maintenance walkway or an access space, surprise! A tungsten lamp is the most green choice. It is best for the environment.
Fluorescents use UV. LEDs use visible blue, sometimes a “blue” as a deep violet color. A LED has far less energy than a halogen lamp. But LEDs have limitations.
Not surprising, a good quality LED lamp’s ranking results are similar to a fluorescent. Both use phosphor to create visible photons. Both create photons in a similar manner. Both have been impacted by legislation changing how the modern lamps perform and shifting damage rates.
Because the damage changes depending upon the material lit, the ranking swaps back and forth between LEDs and fluorescents. Sometimes a LED is better. Other times a fluorescent with a good UV filter is better.
Testing for ranking has been based on top-quality LEDs made by recognized manufacturers with sound technology and excellent color balance.
That needs to be stated again! Ranking has been based on the best made and highest quality LEDs.
For ISO blue wool samples, a “white” LED ranks as more harmful than a UV-filtered fluorescent. For colored samples, a “white” LED ranks safer than a UV-filtered fluorescent. Because this is a comparison, for energy efficiency, currently fluorescent lamps are more energy efficient than LEDs.
The push for converting fluorescent installations into LEDs is to lessen the amount of mercury used in a fluorescent that make the lamp work efficiently. There is an environmental concern. Though the mercury in fluorescent lamps used in large commercial and managed residential buildings has been recovered and recycled since the 1950’s. If legislation continues to lower acceptable mercury content, LEDs will out perform fluorescent lamps for energy savings. The fluorescent lamps become less energy efficient.
Did you catch that?
Older fluorescent lamps were brighter compared to today’s fluorescent lamps. LEDs currently use more energy than fluorescent tubes. But fluorescents are not as good in light quality as they were a few decades ago.
For color samples, a good-quality LED with the correct physical structure for UV filtering will drop the damage rate to 61% of solar. That is a great improvement over tungsten halogen sources. But using good quality, high-tech fiber optic lighting cuts an LED damage rate in half. In half!
To obtain this 67% to 61% number, the LED needs to have a heavy coating of phosphor. The color temperature needs be “warm” in its specification around 3200°K. That means lower energy efficacy. Before you let LEDs take a bow, note that UV filtered fluorescent lamps, MR-16 halogen lamps (not dimmed), IR filtered halogen lamps, and, of course, fiber optic lighting are all less damaging than a good-quality LED lamp with its built-in UV filter.
Bluer (or as the industry states, whiter or daylight color) means the lamp will have an even more accelerated damage rate. The damage gets very close to the same aggressive rates as a cool white fluorescent lamp at 5200°K.
Note also that the LED tested is not RGB. All RGB lamps (LED, OLED, fluorescent, HID) have a problem called “notching”. Any lamp that puts out a spike or dominan How to Pick a Good LED Lamp. Look at the physical lamp. A top-quality LED will have a square or patch of a bright amber-yellow color over the diode at the junction of the semiconductor materials. It can usually be seen upon visual inspection. Different materials used for the diode produce different spectral outputs. These materials are highly specialized. Therefore, stick with known brands. There is enough of an effort to invent better interface materials for energy savings (the latest award is $12M as a grant) that the market is constantly being flooded with unreliable lamps. Thinner coatings or off-color coatings produce more visible light. But thinner coatings produce more blue light with higher rates of damage. Repeated testing shows certain LEDs can embrittle paper in a shorter time period than a basic halogen lamp. Because the “blue pulse” is near the UV, a good LED must also have a substantial lens in acrylic to filter out UV and get the rankings discussed here. The lens cannot be a soft plastic or a styrene. The crystal structure of the acrylic is critical for absorbing UV. Tap the lens. Is it hard? Is it very clear? Does it look thick? If it is not, pick another LED lamp. t single color is producing photons of the same set of diameters (wavelengths) that interact with the material in the exact same way over and over again. The probability of causing chemical change dramatically increases.
It is like a drip of water on a rock. The constant near-identical encounter between the photon (the drip) and the molecules of the material of the object (the rock) stresses that one place. The light wears away the material. It breaks it up, because it is not scattered as rain drops. The “rock” of the artifact is “notched” by slow, continual wear like the constant flow of the individual drips of water.
Why rank an LED below a halogen lamp?
Many museum artifacts are organics. Think paper, natural materials, woods, natural fabrics, fur, feathers, etc. A halogen lamp is safer when the halogen’s heat is controlled with an excellent IR filter and the lamp is not dimmed. For blue objects, LEDs can rank safer than halogen lights, because the light can match the color. But there is always the risk that the dominant blue light will notch the artifact. Until an artifact is analyzed or tested, the effect on the chemistry of the dominant blue is not known.
To complete the discussion, note that LEDs change as the lamp ages. What was once successfully filtered and producing a tight blue color that the phosphor converted into “white” light shifts into more and more of a deep blue light source with lower and lower amounts of the other colors. Older LEDs can become more destructive even though the footcandle levels drop. Fortunately for artifacts, older LEDs can also have half their original visible light output. Overall there are fewer photons produced by the pump system. So the automatic dimming mitigates the damage.
A halogen lamp has burned itself out long before the IR filters have begun to fail. An LED light looses brightness. But it becomes more toxic as it still lights.
So ranking comes with a caveat. A LED lamp can be safer. But it has to meet all the above conditions. And it needs to be replaced well before it burns out. It needs to be replaced when enough phosphors are consumed that the light turns too blue or too cool in color.
With these requirements met, the ranking for an LED is:
CONTENT: zero UV (probably, hopefully…but not always), 75% IR, most above 1200 nm.
COLOR: All colors present with blue bias (cool colors), CRI of 72 (claims as high as 92 which is impossible and as low as 65 which is usually a very energy efficient lamp with little or no phosphors), can determine very distinctive warm whites verses obvious cool whites and can rarely determine a warm black as makes all blacks look cool black. Presentation is not as vivid. Reds turn dull. And color is cooler towards the blues.
CONTROL: LEDs do not have tight focus. The lack of focus in inherent with how an LED works. The beams are messy with scatter, stray light and glare. The beams are usually very smooth with no haloes, dark spots or dim holes. Beams have soft cut off at the edge. But the edge is often hard to identify as the beam drifts into a lot of stray light. At short throw distances, LEDs can vary in color. The beam becomes separated “white” with streaks of blue, green, yellow and red, becoming grainy.
COMMENT: LEDs cut the IR in a room. They save energy by dropping the electrical load and cutting HVAC costs. They use less watts. There is energy savings. Under the right conditions, they are a good choice.
But under the wrong conditions, they are a terrible choice. LEDs can make a space and artwork ugly. The savings in energy can quickly be consumed by problems and short operational life. The acquisition costs exceed the energy savings over the usage of the products. The return-on-investment is negative.
LEDs can make a collection dull and boring.
Fewer visitors. Fewer donors. For private owners, less enjoyment of their treasures. All this is a hidden cost caused by the LEDs.
Light is how artwork and artifacts communicate. The colors are off. Plus there can be so much glare that productivity goes down. In some cases, the glare can cause people to not remain in the space. These are often concealed issues.
These are instinctive observations. These drawbacks are why there is consumer resistance to purchasing and using LEDs. People object to the color. People dislike the glare.
SCIENCE COMMENT: There is another reason a halogen lamp ranks above a LED. LED technology works well for a lot of applications. But where color rendition and protecting things from fading is important, LEDs are a risk. It is hard to sort LEDs for quality.
It is easy to buy LEDs that: 1) do not have enough phosphors, 2) have the wrong colored phosphors, 3) are driven too hard for energy efficacy (too much blue light), 4) have too thin of a protective lens to filter out the UV, 5) have cooling features that do not work well enough to protect from IR buildup meaning field failures, 6) will not update to or match controllers meaning the system has to be replaced early, and 7) have marginal optics generating glare that blind people. (An LEDs poor ability to focus means too much glare on the ceiling creating visual disability. It can be so bad, come installations have people get headaches.)
Halogens also rank above LEDs in relamping. Halogen lamps are consistent. Anyone can replace them as long as they pay attention to the three letter order code of the lamp.
LEDs vary widely in performance and damage rates. Someone with knowledge has to buy the correct replacement lamp as with LEDs, the three letter order code is not consistent in performance. It’s easy to get poor lamps.
Cheaper LEDs are very destructive. These cheaper LEDs have damage rates that climb above the crudest “shop” fluorescent. So be certain to buy quality.
Finally it is IMPORTANT to note that testing is with just-out-of-the-box LEDs. Over time LEDs drop their light output. It can happen quickly. What was bright enough in a year or two is at 70% to 50% the brightness it was when installed.
This is why dimming is so critical for museums. If the LEDs are installed without dimming control, the LEDs exceed the recommended footcandle requirements. Or they meet the specifications when the exhibit opens. But are far below the light levels years later. The shift is slowly over months and months. So it is hard to notice.
The solution is to check footcandle levels every six months. When the footcandles drop to half, change the lamps. Or to calculate based on experience and schedule lamp changes based on operating hours (the calendar). The point is that good collection management replaces aging LED lamps. The dilemma is when maintenance does not change a lamp until it burns out.
Why spend so much time exploring LEDs?
LEDs offer many, many advantages. But there is a lot of mis-information about LEDs and OLEDs. If you have a valuable collection, you need to be very choosy and buy with extreme care.
(Or you can just pick fiber optic lighting for your valuable and precious objects. NoUVIR fiber optic lighting is superior. Or goal is to save the artifacts. That is why we do not offer any LED products unlike some competitors that use LEDs to supplement poor performance in their fiber optic systems.)
Again, always get product from known companies. But remember, a thick acrylic lens is needed to filter UV. And an OLED’s product advantage of flexibility is in conflict with a thick acrylic lens when applied to lighting products.
SCIENCE COMMENT: More surface area spreads out the IR. It lets more IR radiate out the back of the device. But the IR content is still present. Since many OLEDs use fewer watts, the heat in the light will not be obvious.
How do you know there is heat? Take a box and put the fixture inside. If the OLED raises the temperature of the sealed box by any amount, the source has heat. Any OLED will raise the temperature. Most of the time an experiment as crude as a cardboard shoe box will work.
This split white LED lamps into two types - white and RGB.
LED lamps that use a blue diode, a green diode and a red diode to blend light into what appears to be a “white” light use three colors that look white to the human eye. But it is a false white. By changing the output of the RGB, color shifts can simulate other colors. It is an ideal effects lamp.
But the problem with the RGB color is that humans see light reflected off of surfaces. Remember footlamberts verse footcandles? The color gaps between the red and the green and the blue reflect gray data. So objects are not as vivid or appealing as there are gaps of color.
For presentation, the spike of red, green and blue light overwhelm the different shades in red, green and blue. The colors are over saturated to a very certain green, a very specific blue and a very definite red. It is vivid.
But it is distorted. It works for monitors and screens with “thousands of colors” blended. Well, sort of, as it isn’t the same as what artwork produces. This is why using monitors for displaying great art has never caught on with consumers. The color rendition is all over the place. The complexity of color vanishes. Therefore, RGB LED lamps are poor for exhibit work.
However, the lamps are covered in the article.
SCIENCE COMMENT: There are tri-stimulus fluorescent lamps also. The same problems apply. The RGB tends to be more damaging than a white lamp if there is notching and distortion. Testing can show less damage if overall the lamp produces fewer photons. Therefore, use RGB lamps for effects and devices like monitors. Do not use them for artwork.
Again, why spend so much time on LEDs?
Because much of what is published about LEDs is puffery and not factual science. That includes several “how LEDs work” material on the internet. If you have read the article, you now know the data others in lighting do not.
Pick wisely. Don’t let others in their ignorance saddle you with bad or destructive product. Or skip all the careful sorting of LED products and specify NoUVIR.
Further testing shows that cool-white verses warm-white depends upon the object. If the object is “cool” in color with blue shades, much of the time, a warm-white has a more aggressive damage rate. If the object is “warm” in color with yellow and orange shades (browns), much of the time, a cool-white is more damaging. Fluorescents are usually harder on organic materials (natural materials) compared to other types of lighting except sunlight. Does this sound familiar? It is the same type of results as LEDs.
Anything with UV content will embrittle plastics.
Almost always, the more energy efficient the fluorescent lamp is, the higher the damage rate. The more phosphor a fluorescent lamp contains, the safer it is for artifacts. But it takes more electricity to operate the lamp.
Fluorescent lamps that are the least energy efficient with the most phosphors and warmer colors, but not overly yellow, are usually the best compromise. Fluorescents should always be UV-filtered. It is easy to add a 1/4 inch or 3/8 inch piece of acrylic as a filter between the lamp and the artifacts. This removes the UV.
Legislation has been pushing for more and more energy efficiency and for better green disposal. This impact on the lighting industry has degraded the color rendering of fluorescent lamps. Fluorescents do not produce the quality of light they did decades ago.
Did you catch that? If you have an old exhibit using filtered fluorescents, objects looked more appealing several decades ago. Today, because of changes in fluorescent lamp technology in new energy savings efforts… the color presentation and even a drop in footcandle level can now make what was a good exhibit now look ho-hum.
Presentation can be improved in a two lamp fixture by using one warm-white lamp and one cool-white lamp. The lamps have different phosphors. The output blends slightly different colors.
These lamps work together improving presentation. However, if the lamps can be seen, the fixtures look wierd. Remember, films and diffusers work well for cutting footcandle levels. Car tint film is an inexpensive solution for small museums. Mylar drafting film also works and diffuses light.
Notice that different fluorescent lamps, mostly because of the quality and amount of phosphors, will have very different damage rates. They all test in ISO Blue Wool from about 80% to 55% of sunlight. But they will leap frog with slightly different results depending upon type and manufacturer.
HINT: Do not buy your lamps from a discount warehouse or from a home improvement store. Purchase instead from a reputable lighting distributor or lighting industry wholesaler that does not sell discounted lamps. Purchase from a source that knows customers check footcandle levels and CRI. Lamps that fail quality control tend to end up for sale in retail stores where they won’t be returned.
CONTENT: 5% to 7% UV, 70% to 72% IR
COLOR: Colors are present, but with dominant colors blending to “stimulate” a white light and the other colors barely present or not generated at all. A CRI of 70 is common (claims as high as 85 which is highly unlikely to as low as 60 and even 58 for the more energy effective lamps).
Using the light, it is harder to determine colors. A very distinctive warm white verses an obvious cool white can sometimes be identified. Under a fluorescent, it is rare a person can determine the difference in a warm black as all blacks look the same. For colors typically 3 out of every 10 color tiles is mis-identified. Therefore, presentation is not very good. Artwork tends to loose depth. It gets flat looking more like a print than a painting.
CONTROL: Fluorescents for big areas of light work well. Using tubes, the fixtures can have excellent optical control. These tubes can be replaced by LEDs mimicking 4-foot fluorescent lamps. Because fluorescents are older technology, control and glare tends to be superior to LED lights. The industry has spent years using lenses, egg crate, louvers and other controls.
Fixtures with compact fluorescents based on halogen designs can be questionable in control. A spiral, U-shape or circle line fixture can have fair optics to terrible. The area of the lamp is hard to aim. Some downlights obviously waste light as the lamp is not inside the reflector, but the reflector can produce a good beam.
Fluorescent beams are very smooth with no haloes, dark spots or dim holes. Beams have soft cut off at edge. Some fixtures have what is hard to describe as a beam; but is a distribution. Light fixtures using straight tubes with lenses can be gray or dark from the side (good glare control) and produce a beautiful “batwing” spread of light. LEDs will duplicate this distribution in a fluorescent tube replacement.
COMMENT: Unexpectedly, many fluorescent lamps are still more energy efficient than LEDs.
SCIENCE COMMENT: Just like LEDs, quality dramatically changes based on how much phosphor is in the lamp. The phosphors are expensive. But they block light as well as convert UV into visible light. The less energy efficient, usually the better the color rendition. The better the energy savings, the more aggressive the damage rate.
To repeat, “fluorescent” tubes come in a LED format. Follow the above LED check list. Especially be certain the bastard amber filter patch of color is applied to each LED.
Tests using color samples show an increase in fluorescent damage rates. Modern cool-white fluorescents with no UV filtering test at 97% solar damage. The newer, energy efficient lamps can be just as aggressive in greens, the peak color a light meter reads. Therefore, be extremely vigilant. And always get the spectral output to help you predict how aggressive the lamp will attack artifacts.
But if the HID lamp is installed into a fiber optic lighting system, the rank shifts to #2. See above for fiber optics. Most any fiber optic lighting, because the lamp is remote, is better when it comes to protecting objects from damage.
High intensity discharge lamps work by stimulating a mixture of gases in a tiny, short tube or a glass sphere. A blending of metallic salts and other gases create visible light as an electrical current jumps a gap. Each gas tends to make a color. Therefore, the output is like jagged, long teeth with the gaps between the teeth as missing colors. Eventually one of the gases is consumed. The lamp will shift color. Often the shift is a spectacular change as a once white light turns into the color of an orange parking lot light.
“What is one of the worst lighting design mistakes you ever made?”, attendees were asked at a college-accredited NoUVIR seminar on lighting. An architect answered, “I put an HID fiber optic system in the office of my boss. Everything was fine until the whole office turned orange.”
HID lamps can have different blends of gases. So the photon output has a wide range in UV and IR. The color change can also be different depending upon the gases and mix. The gases are never a perfect blend. Warning: New HID lamps from the same manufacturer and same manufacturing lot will have slightly different colors right out of the box. Commercial users for indoor spaces will often sort their lights to put matched lamps in the same space.
CONTENT: 10% to 21% UV, 65% to 54% IR (roughly 25% visible)
COLOR: Colors are a blending, usually RGB with an orange added for warmth, to simulate a white light with other colors weakly present or not generated at all. A CRI of 65 is common (but with the changes and today’s fuzziness in how CRI is calculated, claims are as high as a CRI of 85).
CONTROL: HID lamps have a tight enough packet that they focus well for outdoor uses, warehouses, atriums, large platforms, etc. However, because of the heat content of the source, they are hard to filter for UV content.
COMMENT: These lamps make good outdoor lights for a variety of uses as well as work in large interior spaces. These commercial applications often use scheduled lamp replacement to counter the color change.
Many indoor uses can be questionable. Color rendition should never be a requirement. The lighting can be harsh and quite appalling in a room.
Because an HID lamp can output a lot of footcandles, HIDs are used in projectors to light large bundles of fibers. These lamps have powdered architectural fiber optic systems for decades. Architectural fiber optics work as substitutes for neon, fountain lighting, accenting skyscrapers, pathway lights embedded in concrete, hazardous room lighting, chandeliers in high-ceiling rooms where color and footcandles are provided by other lighting, bridge lighting were access is difficult, dock lights where constant flooding corrodes, etc. Just as HID lamps used in fixtures are group lamp replaced, fiber optic systems should depend upon lamp replacement before color shifts become ghastly.
HID fiber optic systems are not the best choice for collections. Scheduled lamp changes can overcome disturbing color shifts. But a new lamp distorts specific colors as well as turns certain colors gray. A CRI of 65 means 35% of colors are mis-identified. Frankly, the light makes things and even people look ugly.
Why are HID fiber optic systems sold to museums? A HID lamp can produce enough light to seriously illuminate things.Why are HID fiber optic systems a bad idea in museum exhibits? Because the outside of a building can have terrible color. But artifact lit that way makes the exhibits unappealing. A collection needs to be beautiful. It needs to show detail. It needs good color. It needs to bring back visitors and impress donors. This is why CRI is so important. You want 100% of the colors to show.
SCIENCE COMMENT: White papers take a lot of time to write and review. But this subject is briefly covered in an excerpt from the book, Protecting Museum Exhibits From Their Environments (And Vice Versa). If you consider a HID system, pay close attention to the lamp cost. Some fiber optic systems use lamps that are more expensive than a complete NoUVIR projector.
About every 40 years architects and the lighting industry go through an exciting “new” trend in sunlight. The statements are always the same. “Sunlight displays the best presentation.” “Sunlight is so natural, it makes spaces more comfortable.” “Sunlight saves electricity.” “The industry needs to use daylight.” “Buildings need to be flooded with natural light.” The industry is flooded with articles, seminars, classes and award-winning projects.
But it is of false economic benefit. Sunlight is hard to limit. Even with computer controlled louvers, metal screens, tints, printed graphics on windows, special shades, automated drapes and vacuum-deposited filters on glass, the intensity, color, direction and availability of sunlight is always changing.
For museums, it is hard and expensive to meet the recommended footcandle requirements. And it is not just the intensity. It is the color.
All sunlight is data filled. Every color is present. But the light has more reds in the mornings and evenings with the light being most blue at midday. The sun itself is a consistent spectrum. But the wavelengths are filtered by more or fewer layers of atmosphere. Then add in weather, nighttime needs, maintenance…but when the fad is going, architects and lighting designers tend not to listen to reason.
Then add in the green enthusiasm. Surely sunlight is energy saving. Few know the facts. Windows are never energy efficient. The very, very, very best and most expensive thermal glass window is not as effective for HVAC as the most common, average drywall wall. Did you catch that fact? The most expensive, high-tech window still bleeds more energy out into the outdoors than the most boring, basic wall.
During these fads, many interesting and beautiful buildings are built. Windows, walls of glass, atriums and skylights abound. Then the sunlight trend fades away as people live with the implications of intense maintenance and higher heating and cooling costs. The generation with experience retires. And sunlight comes back into trend like a heatwave.
Today we are nearing the end of the latest fad. There are some incredible buildings coming out of this movement. But there are also some very expensive, impractical designs. And there are buildings that have become major disasters for their museums.
CONTENT: Too much UV. Too much IR. Too much unreliable, visible light from clouds, rain, etc. Do not use sunlight to light collections.
COLOR: All colors present, but colors change throughout the day. Do not use sunlight to light collections.
CONTROL: Most daylight buildings have marginal control. Those that use very expensive controls. find the systems fail over time. The recommendation is to block sunlight. Drapes, graphics, heavy tints, curtains, blinds, netting, walls, shades, graphics, metal mesh, built in cases, portable screens, fabrics, dense foliage, light blocking stained glass, sandblasted patterns, Victorian blinds, outdoor walls, pull shades, boarding windows up…the solutions are endless.
COMMENT: If an architect wants to use lots of glass, even for just the lobby, find another architect. Sunlight and beautiful objects do not play well together. Sunlight is 7,000 to 10,000 footcandles. A good museum exhibit needs to display rare treasures at 5 to 10 footcandles.
Case Study #1: Energy efficiency alone is the wrong goal for any museum. The new building was a marvel to behold. It won awards. It was featured in magazines. But it turned the museum’s operating finances upside down. Tickets are $65 per visitor. Yet it barely pays for the building’s current overhead. This is a brand new building. Maintenance is minimal compared to future years. The board wonders about survival.
Case Study #2: A museum has an impressive, three-story tall sunlit lobby that flows light across the whole front of the entrances to the galleries. Visitors are exposed to the lobby every time they exit a gallery. The sunlight, even with heavy tinting, is far beyond the 2:1 ratio for light adaptation. So the lobby stops the museum from exhibiting artifacts in a 1/3rd of its building. And because 15 minutes is required for light adaptation every time a visitor is exposed or re-exposed to the architectural grandeur, the most important objects are displayed in the far back of the museum furthest from the lobby. The museum is in serious financial trouble. Its doors closed. This was before COVID. Today its doors are still closed with no announced plans to reopen.
Case Study #3: A building is made of floors centered around a tall skylight. Every floor is a perimeter that opens to the grand, central space where a visitor can see not only the rest of the floor across the beautiful, railed gap; but look up to the large skylight and down to the first floor. Massive humidifiers and HVAC systems try to stabilize the building. More and more equipment is added. But it still rains indoors under certain conditions. All the significant documents and rare book exhibits are in the basement. The most valuable documents are off-sight.
Case Study #4: A historic house museum built spaced additions of modern bathrooms to accommodate bus tours. The architect used beautiful, scenic windows to display the historic grounds and add daylight. But the visitors loose their light adaptation. They go to the bathroom and are blind for 15 minutes until their eyes adjust to see the house and its treasures. The rarer objects have now migrated as far from the bathrooms as possible. Infestation has also become a challenge. Enough light enters that alga grows in the toilet water.
Case Study #5: Four large historic art galleries were reroofed with skylights, computer controlled louvers and a fortune in equipment to assure daylight would never exceed recommended footcandle requirements. The daylight would show off the art. The sun would be defused and filtered, never shining directly on a masterpiece. The design was heralded as excellence in energy efficiency, and brilliance in lighting design. The reality was the controls, louvers, flaps and shutters cost more in energy to operate than the museum’s old halogen lighting system. When the museum started experiencing maintenance costs, the skylights were covered in tarps and eventually painted over. The museum returned to a halogen track lighting system. Great fanfare surrounded the first conversion. The magazine articles claimed “daylight was finally viable” for museums. The second conversion was done with hushed whispers.
SCIENCE COMMENT: Daylight building designs harm museums and their exhibits. Architects can design stunning buildings. But they unintentionally cripple the museum for decades.
Help Matching Artifact Needs to Light Sources
Test results have ranked these light sources. Over the decades numerous tests have been run by NoUVIR using a variety of materials, samples and fragments supplied by scientists, various conservators and artists. The list of testing materials include, but is not limited to:
- old papers (medieval to 1900’s), modern papers, color papers for copy machines, Post-It® Notes, newspapers (late 1800’s to current), handmade papers (cloth to grasses), papyrus (old fragments to modern reproductions), assorted cardboards, artist framing mattes, paperback book covers,
- writing inks (natural squid to modern gel ink), printing press inks, modern dyes, natural plant and root dyes, edible safe colors used in foods,
- chalk pigments, color pencils (modern, but different grades from children to artist materials), commercial color pens, historic watercolors, modern watercolors, known fugitive watercolors (suggest the book, The Wilcox Guide to the Best Watercolor Paints by Michael Wilcox), historic oil paints, fugitive and known unstable oil paints, modern latex craft paints,
- metallic paints, gold leaf samples, spray paints, modern house paints,
- natural rubbers, synthetic rubbers, dried flowers, dried leaves, dried grasses, bird feathers (all colors), insect wings and butterflies, commercially-tanned leathers, old tanned leathers (pre 1900’s), “leather” papers, rawhides, treated intestines (Native American), furs (rabbit to old mink), bones,
- jade, amber (including amber trapped insects), pearls, ivory, shells, carved shells, agates, soft and crystalline minerals, marble stone, granite (including decomposed), volcanic rock, cement,
- “tarnished” and “polished” metals (silver, lead, copper, etc.), color anodized aluminums, gun bluing (various historic kinds),
- natural glues, synthetic glues, glued laminates,
- a wide variety of woods and wood finishes, natural varnish, polyester finishes, urethane finishes,
- cottons (historic to modern), various silks (historic to modern), linens, linen blends, polyester fabrics, nylon fabrics, modern fabric blends, velvets, colored felts, sequins, Civil War uniform threads, painter canvases, natural hemp,
- pre-plastics like Bakelite, styrene, acetate film, modern sheet plastics, modern molded plastics, variety of waxes, staining oils,
- modern postal stamps (no label stamps), and
- 3-color artist prints, postcards, photographs (old, black and white, old color), historic photographs, 1950 - 1970’s color photographs and modern color photographs (digitally printed).