photochromic dyes may do this job.
>Subject: ORGLIST: Interested in measuring sun exposure via predictablereaction
>Date: Sun, 17 Jul 2005 17:52:01 EDT
>I hope I'm using this list and group correctly - I just joined.
>I'm interested in measuring how much sunlight gets to a particular spot.
>Here's what I have in my mind that would achieve the result I'm looking for..
>it doesn't have to be exactly this method but this would be ideal:
>I envision a small card or strip of paper (like litimus paper strips) that
>was immersed in a chemical that is predictably reactive to sunlight. As the
>exposure increases it would change color - and when a measurement is desired the
>color of the card would be
compared to a chart.
>Is this possible? Is there such a chemical in a form that can be used like
>Thanks for your help,
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