Optically Variable Color-changing Inks
Color changing inks are inks containing pearlescent pigments that change color when viewed at a different angle. The color of the ink does not actually change, but the angle of the light to the viewer's eye changes and thus creates the change in color. A number of types are available, including green to purple, gold to green and green to lilac.
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Famous quotes containing the word variable:
“There is not so variable a thing in nature as a lady’s head-dress.”
—Joseph Addison (1672–1719)