Light damages textiles, but how?
Light, especially ultraviolet light can fade colors, turn whites to yellow, and even weaken the molecular structure of the individual fibers in some delicate fabrics. Over long periods of time, fabric will turn to dust, as I once observed while touring the stately home, Knowles, in England.
Light is countless bullets called photons
This is where we need to take a quick look at quantum physics, tho all we need talk about is a little item called wave-particle duality.
It has been shown that light behaves as both wave AND particle. This is difficult to visualize because nothing in our everyday lives behaves this way. We either experience waves, such as on a surface of water or on a vibrating string, or particles such as dust or salt grains. We never see both properties occurring together.
reflected rainbow, pshab
As a particle, light can be sub-divided down as far as a single “quanta” of light known as a photon.
The best way to visualize this process is to use an analogy. Light can be thought of as countless tiny bullets, smaller than atoms. The amount of light (how bright) is how many bullets; the color of the light is how powerful the bullets are.
The familiar rainbow spectrum of visible light spans from red to violet.
light spectrum, moostive
Red light is least powerful – violet light is most powerful. Ultraviolet light has a lot more energy than visible light. (The bullets are magnums!) So for a given amount of light, ultraviolet can do a lot more damage. This is all we need to know for our purposes.
Remember, the photons are the bullets. For a given frequency, a photon has a fixed amount of energy. So for a given color of light, there are a whole bunch of photons with the same energy.
And the bullets upset the molecular “glue”
The molecules that make up different fabrics are held together with different molecular energies. Molecular glue if you like. Delicate fabrics’ molecules are held together less strongly than those of tougher fabrics. If a photon with enough energy comes along and collides with such a molecule, it can impart enough energy to disrupt the molecule, creating two separate parts that are no longer the same material. This is the process that, if repeated often enough, will cause discoloration and possibly even destruction of a delicate fabric.
(It is also why ultraviolet light damages our skin while visible light has no effect. The energy in visible light is not sufficient to cause molecular disruption in our skin.)
It’s all a matter of scale
There is no magic level at which fabric is either safe or unsafe. Damage is directly proportional to how much exposure to light the fabric receives and the energy level (color) of the light involved. Keep down the proportion of time the garment spends in the light, especially high energy light such as ultraviolet, and damage will be minimal.
This post printed with permission from Sentinel Archiving. Permission for photos at Flickr approved, photographers names shown for each photo.
