Toothpastes (and other products) that advertise with whitening are using fluorescent chemicals that stain your teeth, laundry, paint, etc. These chemicals, commonly known as optical brighteners, absorb invisible UV light and reflect it back with a lower frequency wavelength making it visible. Of course, the closest visible wavelength to UV is blue so the bright white light that is reflected has a bluish tint to it. Now, a property of our color vision is that our eyes take the brightest white in our vision and use it as a reference to judge all other color in our field of view. As objects that are stained with a fluorescent optical brightening agent are reflecting both visible and UV (invisible) light, they will always be the brightest white objects in our field of view. With this object as our white color reference, a true neutral (6500K AKA average sunlight) white will appear yellowish to our eyes. What this means is if youre wearing a white T-Shirt that is stained with an optical brightening agent it will appear to be BRIGHT white to your eyes, when it is actually blue. While wearing that shirt, even if your teeth are perfectly white, they will appear to be yellow. Optical brightening agents in toothpaste became popular a few years after optical brightening agents became popular in laundry detergent / bleach. Why? The answer to this is incredibly hilarious to me, people started dying their white teeth blue to match their shirts!
Posted on: Sun, 24 Nov 2013 22:00:49 +0000
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