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<p>[QUOTE=&quot;desertgem, post: 1300591, member: 15199&quot;]Several studies of factors determining the total amount of UV radiation at a geographical location have indicated that altitude and closeness to the equator are the most consistent factors. The largest study says the effect of altitude varies from 9% to 24% per 1000 ft. So much more UV at Flagstaff @ 7000ft compared to San Diego @less than a 1000. That said, I feel that UV effects on metallic silver would be zero if the metal was in a vacuum and the UV was at a maximum environmental level on earth. Studies on nanoparticle size of silver may have quantum type reactions, but a silver coin is not nanosized.</p><p><br /></p><p>Most older experiment using UV and water did not eliminate such factors as the amount of ozone. UV can break down ozone and release reactive oxygen singlet that then can react with metallic silver. </p><p><br /></p><p>I think for silver objects it is still environmental factors such as ozone, H2S, etc., than UV levels that determine any tarnishing. So if you can&#039;t change the environmental factors , use the tightest sealed holder. IMO.</p><p><br /></p><p>Jim[/QUOTE]</p><p><br /></p>

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