Perhaps you're thinking of Vostok? I thought much the same when I saw it in the Science Museum in London (just last weekend). Some kind of heat resistant cork or something? http://www.sciencemuseum.org.uk/ImageHandler.ashx?image={4D8...

I can heartily recommend the Cosmonaughts exhibition if you're at all interested in the birth of the Space Age. It's open till the 12th of March: http://www.sciencemuseum.org.uk/visitmuseum/Plan_your_visit/...