18 May
2012
18 May
'12
5:50 p.m.
I don't know what happened, but that post went before I was ready. Finally, I found the article I was looking for. Dr. Chou wrote an article in 1988 and it was published in Sky and Telescope, Aug, page 119. I found that article or a similar one, here: http://www.mreclipse.com/Special/filters.html Dr. Chou tested many different types of filters including Pop Tart wrappers, photographic film, smoked glass etc. He gives the result in this article along with the criteria for safety and the safety factors designed into solar filters. It is very good reading.