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http://www.instructables.com/id/EHJ31ZVF1A4XXDG/
This is the link. I think you could make it more accurate than this example. I guess I will have to try it sometime to see if it works. I have some...

I just read an article on wood burning. Normally you do it with a soldering iron style pen, but in this demo it uses metal tape, and the sun. Just mask off the unwanted area and burn with a...