Reflected light does not create chemical change. Absorbed light does.

The more photons absorbed, the more damaging the light source becomes. Mismatched photons enter atoms and break up the molecules. The original molecule becomes two molecules.

Since different light sources make photons in different ways, knowing how each light works and what the light output is lets light sources be matched to what objects they are lighting. Light sources can be ranked by how many photons create damage.

Here are light sources used in museums ranked through testing.

Sorting Light Sources

As can be seen, different light sources produce different photons of different wavelengths of light.

The atomic structure of an object is impacted by this output. The paired particles either match the object or mismatch the object. Controlling what photons are present is really a way to control what photons the object is exposed to and that in turn controls the damage rate. It is all based on the quanta or actually the probability of a photon being absorbed into an atom.

The science can be made very simple.

Matched light means good presentation and very little damage.

Mismatched light means poor color rendition (things look more lifeless and boring). Mismatched light causes harm. Mismatched light changes the chemistry. It produces damage. The more in quantity of mismatched light a lighting source has, the more damaging.

First Step - No Light Below 380 nm. No UV.

Good practice in lighting something valuable is to remove any light that is invisible. No UV. No IR. It is where our trademark, NoUVIR®, came from as it is a promise that NoUVIR fiber optic lighting is completely without UV and completely without IR.

Both UV and IR content in any light source never generates sight. It only has the potential for harm. Therefore, the amount of UV and IR in any light source that is not fiber optic lighting impacts the rate of damage.

(Beware. The lighting industry uses marketing puffery stating LED sources are UV and IR free. A hint this is not true are the heatsinks on the lamp. But it is common for LED spectral output curves to end at 900 nm, never showing the IR.)

Ultraviolet light cannot cause sight. It can only cause damage.

And since its photon is a tightly spinning particle pair, UV tends to create damage deep down inside an object.

UV is the light that often structurally breaks up or weakens a piece of art internally. It will embrittle the paper of a rare document. It will yellow and weaken the threads of a costume. It will accelerate cross linking and collapse structure. It will break a piece of ivory or bone in two. It will rot the threads in a costume. It can structurally cause horrendous damage.

The chemical changes happens deep inside where conservators have a hard time even seeing problems until the structure breaks or physically crumbles to powder internally.

(This is why a common archive standard for documents is that no light should be below 500 nm. Ultraviolet is 380 nm or less. Light from 380 nm to 500 nm is visible purple and blue. The UV, visible purple and visible blue light is absorbed and fades as well as breaks up the structure of the paper, because old paper is often yellow, brown or red color.)

Second Step - No Light Above 770 nm. No IR.

Infrared cannot cause sight. IR can only cause damage. And since its photon is a wider spaced spinning particle pair, it tends to generate damage on the surface of an object.

It also is a great way to increase chemical reactions. One noteworthy conservator of a world-known institution says, “I tell them, ‘Use any other lighting (speaking of fiber optic light with zero UV and zero IR content) and you cut the artifact life in half. In half!’” He further explains that this is because even a small rise in temperature on an artifact’s surface or inside a case accelerates damage rates.

(Remember high school chemistry? A Bunsen burner accelerates chemical experiments. It adds IR. The more heat, the faster the reaction. Or in other words, the more IR photons, the faster the photochemical reactions.)

Third Step - Balanced Visible Light

Quantum physics is all about probability. What are the odds that energy (a photon) will excite matter (an atom) and cause change (quantum change)? The measurable, invisible light can only cause damage. The probability of visible light generating a quantum change is less. Visible light has a higher probability of reflection.

(It is like playing poker. Take a deck of 52 cards. Shuffle. Deal a hand. But play the original “old army game” where the hand dealt is the hand you play. There are no discarded cards. Did you get a winning hand? Probably not. The odds are against you.

Light is the same. Most photons do not reflect. They are loosing hands as the photons are absorbed. The winning hand have photons that are reflected. These photons do no harm and can cause sight.

By removing the UV and IR, you remove the cards with numbers from the deck. Now the probability has shifted from 52 cards to shuffling 12 face cards plus the aces or 16 cards. As you deal more and more hands, more hands are winners. If you perfectly match a monochromatic object like a document, the probability shifts further. Play cards with just the aces. You have cheated the probability of light damage as it is impossible to be dealt a bad hand.)

The better the light matches the object, the longer it will last. The more the light mismatches an object, the faster it will deteriorate.

The good news is that we are wonderfully made.

Humans see mismatches in the visible spectrum. As an example, go back to the ISO blue wool testing. The blue fabric lit with full spectrum light looks blue. The ISO blue wool samples reflect blue photons. The data returned to the eye is blue. The green, yellow, orange and red are absorbed. The UV and the IR are also absorbed.

Humans do not miss data that is not reflected.

Therefore, using a blue filter, the fabric samples look identical to those lit with the full spectrum. The same data as photons are returned to the eye as reflected blue. But, and it is big difference, the green, yellow, orange and red are no longer absorbed. Test subjects cannot identify the difference in the lighting. The data “seen” is the same.

(Over 25 years ago, an internationally-known lighting expert-of-experts disputed Reflected Energy Matching Theory stating that humans would be able to see and detect the missing colors. Reflected energy matching would distort. Even the most subtle color filtering would be unacceptable, n o matter how much more it extended exhibit life. The expert was adamant.
At a National Park event for scientists and museum professionals, the expert was asked to examine a case with 5 objects lit by fiber optic lighting with only one object having the added feature of stacked colored filters. He and his entourage could not pick out the further matched object. He chose three wrong objects, none of them with further visible filtering. Note that removing all UV and all IR is already applying reflected energy matching. But further matching can be done with filters.
Again, the expert picked three wrong artifacts. Once told, he could still not tell the difference. To further prove you cannot miss absorbed light, the object lit with color filters was a rare book in a support cradle. Half the book was lit with pure-white NoUVIR fiber optic lighting using all the colors of and as white light. The other half was illuminated with color filters stacked to exactly match the paper color of the page. The same book, page beside page, and the difference could not be detected. But the science shows the fading damage rate dropped 40x.)

Absorbed light causes damage. Reflected light does not cause damage. If an object looks great, chances are the visible light is reflecting off the object as data. If an object looks lifeless and colors are skewed, chances are mismatched visible light is distorting and being absorbed. The damage rate is usually higher.

Back to the blue wool samples, if the samples are lit with red light, the blue wool turns black. Humans see the mismatches in the visible spectrum. Tests show that the mass majority of damage is caused by the red light compared to the blue light. Therefore, presentation, what you see, is strongly connected to preserving an object.

First remove UV. Second remove all IR.

Then ask questions about presentation.

For multiple colored objects with great variety, balanced white light is the best. Every color should be in the light source. But if the light source has a certain color that mismatches the reflection of the object, poorer CRI can increase the photochemical damage.

Mismatched visible light makes things look boring and grayer. The damage rate is usually higher than it should be. If things don’t look good, chances are the photochemical damage rate is much higher than it should be too. It is an indication of harm. Presentation and preservation go together.

Fourth Step - Matching Visible Light

This basic understanding of quantum physics has a practical application.

It lets someone rank light sources and predict what is safe in lighting for an object and what is dangerously damaging. It is all tied to what a photon is and how it reflects as data or is absorbed generating damage. It is the science of how things work.

Skewing the probability of damage can be sorted based on bias outputs of light sources. Fiber optic lighting is stone-cold, pure-white light. But what about other sources?

This is where the dominant or most fragile color of objects can become important knowledge. Light sources have bias. A blue dress will be damaged less by an LED lamp than a red dress. A brown document is more resistant and lasts longer under the yellow of a low-watt halogen lamp even though the lamp has lots of IR, because the document does a pretty good job of reflecting IR. A fluorescent lamp will be better for uncut gems and minerals, because the heat is less compared to a halogen light.

Sorting light sources is done by looking at each light sources’ spectral output. It has to be ALL the output. The volume of photons in certain wavelengths can be compared. Picking and matching light sources is all based on a knowledge of those photons.

See the button LIGHTING SCIENCE FROM FOSSILS TO SPACECRAFT on the home page. It is right were you were when you clicked on these questions about light. In the section you will find each light source ranked for damage, UV content, IR content, color (CRI), beam control, comments, science comments and links to specific pdf papers on each light source with how each lamp works, the science of how the the photons are created, spectral output charts and even photographic comparisons for presentation.

Use the “Jewel of Physics”

The genius physicist who worked on the Manhattan Project, Dr. Richard Feynman, put it this way when asked about what was the most important fact for mankind to know. “It is (quantum electrodynamics), therefore, I would say, the jewel of physics - our proudest possession.”

Why do you need to know the basics about this jewel of physics?

Because today the lighting industry is flooding people with misinformation, particularly published on the internet, that skews science and misrepresents product performance. Real world physics debunks marketing claims. It sorts out confusing explanations.

Lighting products can be sorted. Artifacts can be protected. You can specify products using applied science. Your knowledge can save thousands upon thousands of dollars in avoiding photochemical damage.

People say “light” is a wave. People say “light” is energy. People say “light” has no mass. These people are wrong. These statements are half truths.

Light is made up of particles. The photon is an electron and a positron spinning around each other. The distance between the electron and positron determines the wavelength.

Photons cause photochemical damage and photomechanical damage. Picking the right light source can dramatically reduce damage rates. Using the wrong light source can accelerate damage. Since condition is a major factor to value, care should be taken in specifying the lighting. And it is not just museums. Private collections are the museum exhibits of tomorrow.

(A final word supporting that photons are made of particles. Albert Einstein demonstrated photons had mass in 1915. Observatories around the world noted starlight being physically turned by or bent by the forces of gravity during an eclipse. This was proof positive photons were particles with mass pulled by gravity. Waves would not have been influenced by or bend to gravity. The event gave birth to quantum physics. In 1923 Arthur Holley Compton would show that radiation acted as particles and name this speeding quantum, “photon”, from the Greek word for light. In August 6, 1945, at Hiroshima, irrefutable proof was provided to the world in the ultimate demonstration of applied science. Breaking an atom not just sheered its interior, but threw electrons off as massive radiation, or in other words, light, with the photon particles breaking apart matter in catastrophic photochemical damage. The same physics that leveled a city is working at just a far, far slower pace on your collection through the lighting system. But you can accelerate or greatly retard the damage by wisely applying science to choose the right lights for the objects.)

You need to pick your lighting.

Not the architect. Certainly not a contractor. Not even the exhibit builder. YOU!

Lighting is too important when it comes to enjoying and protecting valuable collections. What are the things you can do? Here are examples of NoUVIR fiber optic lighting in use as applied science.

Artifact Lighting Examples