These NASA-surplus tantalum foils have been anodized to various attractive shades of green, pink and purple. Not sure if NASA wanted them colored this way, or if it was just accidental. I have a story about how anodizing works: It's about titanium, but the principle is the same for any metal that forms a clear oxide layer.
Source: Ethan Currens
Contributor: Ethan Currens
Acquired: 1 July, 2006
Text Updated: 19 November, 2007