I worked in a fast food restaurant before college. I would be on the closing crew about three or four days a week. I would usually be the one washing and scrubbing the crusty broiler parts every time.

When I got to college, they gave everyone Thinkpads with fingerprint readers. Mine had trouble reading my fingerprints for about 2 months. I guess that I scrubbed my fingerprints away with all that grease, and it took that long for my fingerprints to "regrow" enough for the sensor to recognize them.