Good Librarian (Pat, Pat)

My first day back at work yesterday, and right after I whined on my blog about being bored, we answered a reference question to the great satisfaction of all parties.

Mr. W. calls us regularly, and he always has an interesting question. Last time, he wanted me to find out which metal conducts electrical currents best (copper, gold, etc.). That was fun.

Yesterday, he wanted help to remember a word, and this is the metaphor he built for me to explain what he was looking for:

'On an old manual typewriter, you have the roller, and you have small hammers that hit the roller when you strike the keys. The hammer makes an impression in the roller that stays only for an instant, and then the roller bounces back to its original shape. What is the word for something that takes an impression but bounces back to its original shape? It is the bouncing back-ness that I am most interested in.'

I said that I would work on it and call him back. After a few minutes of pacing in the thesaurus aisle, I knew the word started with 'R'. After a few conversations with my colleagues, we struck upon it.

Go ahead. Take a guess what the word was.