I've never heard of the custom of washing after an eclipse. Must be a regional thing.
May I direct you once again to Wikipedia for info about solar and lunar eclipses. Googling "eclipse viewing" (without the quotes) will give you instructions on how to safely view a solar eclipse.
- No light effect that I can think of.
- For a lunar eclipse, no effect at all. For a solar eclipse there is a benefit -- less sun on the skin means less sunburn. On the other hand, less sun on the skin means less vitamin D is produced. But these are positively minor compared to night.
- Yeah, probably just a custom driven by superstition.
- You can look at a lunar eclipse all you want. But NEVER NEVER NEVER look directly at a solar eclipse (or the sun for that matter) without adequate protection.
"For shame, gentlemen, pack your evidence a little better against another time."
-- John Dryden, "The Vindication of The Duke of Guise" 1684