You know, [skin] happens at the gravy boat stage - right? - or this happens when you're trying to keep it warm. So the way that I avoid this is I keep my gravy - the second it's done, I put it in a thermos, which will keep it hot and will prevent air from getting to the surface. And I keep it there till the last moment. The last thing that goes out to the table is the gravy, and I pour it out of the thermos and immediately move it in.
Alton BrownLast year, I made a refrigerator in my basement. And I needed to because I needed to figure how - you know there is no such thing as 'cold.' There is only less heat.
Alton Brown