While it appears to darken in the sun like Transitions eyeglasses, the trigger is heat not UV exposure.

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Then, when snow or rain wash them onto an ice floe, they darken its surface and thus cause it to melt faster.

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If we see a person first in a good light, it is difficult subsequently to darken that light.

ECONOMIST: Idea

Economists noted that although the job picture didn't brighten significantly in June, it also didn't darken further, despite worse news in Europe and signs of a slowdown in China.

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Latisse could potentially cause hair growth if it drips on the face or darken eye color, but eye-color changes weren't seen in Latisse clinical trials, Allergan says.

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