I was thinking about this, but cannot grasp why it should or should not be possible. I understand that light can excite molecules and make them emit visible light. But I'm talking about using, say hypothetically, a particular wavelength of visible light to permanently convert a material into a new color.
Aside from photobleaching, is it possible to stain a material with light?
- Thread starter gururu
- Start date
There?s no doubt that light can cause color changes. I know little of photochemistry so I can?t say if the changes are permanent. I know color changes are made to occur using ultra-violet or infrared wavelengths. I?m not aware of any color changes due to radiation in the visible spectrum. I recall a ?thermo chromic T-shirt? fad from a few years back. Those shirts when exposed only to sunlight would change color. Fading is due to the decomposition of the dye molecules, which would satisfy your question, but I don't think that?s what you were after.
Here's a little anecdote about how I made a light-sensitive T-shirt.
I once cleaned up some spilled part-used 'fixer' in my darkroom using an old white T-shirt. Being lazy I let it dry, before deciding to wash it. I did wash it, but it was badly stained.
Where the fixer had contaminated the shirt, it had been stained grey-brown. Forgetting what had stained the shirt, I tried bleaching it - and within seconds the stain had vanished. After washing it conventionally, I put it away and thought nothing of it.
I picked it out a few days later, still nice and white, and wore it to do some work in the garden. After an hour or so out in the sun, the staining had reappeared, but this time a deep black.
I wore it several times, bleaching it to make it white, and then have it change colour again in sunlight.
I once cleaned up some spilled part-used 'fixer' in my darkroom using an old white T-shirt. Being lazy I let it dry, before deciding to wash it. I did wash it, but it was badly stained.
Where the fixer had contaminated the shirt, it had been stained grey-brown. Forgetting what had stained the shirt, I tried bleaching it - and within seconds the stain had vanished. After washing it conventionally, I put it away and thought nothing of it.
I picked it out a few days later, still nice and white, and wore it to do some work in the garden. After an hour or so out in the sun, the staining had reappeared, but this time a deep black.
I wore it several times, bleaching it to make it white, and then have it change colour again in sunlight.
It depends on what you mean by "permanently convert a material into a new color." The color of an object is a property of the molecules reflecting light. Unless the light can change the molecule, no color change. There are photochemical reactions -- photography is a great example -- but it is the change in molecules caused by light that makes the change. The molecule after the photograph is taken is not the same as it was before the photo was taken. Color, especially bright colors, are often associated with double bonds in the material. These double bonds are more susceptible to breaking under some circumstances. UV light often breaks these bonds and you get color fading. It doesn't take UV light, but UV light is more destructive.
okay, i'll bite into this. NO, and depends on the material. I will use the term LIGHT very loosely...
First, you have to remember how light works, and why certain materials are certain colors. Visible light has a spectrum, wherein various wavelengths appear as different colors. That is to say, color light is differentiated by there wavelengths. When an object is hit with WHITE light, light of a bunch of jumbled wavelengths, the color that is reflected is the color that is NOT absorbed by the material. This is what happens when light is REFLECTED from the object. What happens if excited electrons jump energy states and release photons is related, in that the wavelength of the emitted photon dictates the color being emitted, assuming COLOR is a correct description of that wavelength (it can fall in the UV range for all we know).
Now, typically, a substance would not change color, since the color it reflects is inherent in its molecular structure. What makes it change color is when a the light that is hitting causes a chemical change in its structure. This can be because the energy being absorbed by the material breaks some bonds and\or causes new ones to form.
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Contrary to what CTHo said, no this is not how CDRs work. CDs work by reflecting and directing a laser beam TO or AWAY from the detector. CDRs work by modifying the substrate such that the laser is allowed to be reflected toward or away from the detector. This is not a modification of COLOR, its a modification of its reflectivity\refraction index.
First, you have to remember how light works, and why certain materials are certain colors. Visible light has a spectrum, wherein various wavelengths appear as different colors. That is to say, color light is differentiated by there wavelengths. When an object is hit with WHITE light, light of a bunch of jumbled wavelengths, the color that is reflected is the color that is NOT absorbed by the material. This is what happens when light is REFLECTED from the object. What happens if excited electrons jump energy states and release photons is related, in that the wavelength of the emitted photon dictates the color being emitted, assuming COLOR is a correct description of that wavelength (it can fall in the UV range for all we know).
Now, typically, a substance would not change color, since the color it reflects is inherent in its molecular structure. What makes it change color is when a the light that is hitting causes a chemical change in its structure. This can be because the energy being absorbed by the material breaks some bonds and\or causes new ones to form.
--
Contrary to what CTHo said, no this is not how CDRs work. CDs work by reflecting and directing a laser beam TO or AWAY from the detector. CDRs work by modifying the substrate such that the laser is allowed to be reflected toward or away from the detector. This is not a modification of COLOR, its a modification of its reflectivity\refraction index.
-Really? I assumed it was a modification of it's transparency? Modification of refraction index? You're not talking about CDRW here? BTW, how do CDRW work? I only know it's some kind of phase change rather than modification to a dye.
Depends what you used to color them. Some dyes and some pigments fade very quickly. Others are more stable. Some even stay completely unaffected by light.
Some develops color like patio furniture. They start white, but they eventually turn yellow.
A lot of aqueous silver chemicals darken upon exposure to light as well.
A lot of aqueous silver chemicals darken upon exposure to light as well.
sao123
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