sealing a cardboard tube?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" <Beans45601-at-aol-dot-com>

I just got sonotube (cardboard tube) from homedepot that I will eventually 
wind my secondary coil on. I know first, to wype it down with an acholed 
(is that a word?) rag. But, to seal it, what should I use? Also, they sell 
circles that are (.5" wide, not sure...) made of mdf. They don't have the 
size I need (or course), so I was thinking it would not hurt anything to 
have an inch or two hanging over the side. I could get my friend too cut it 
to the right size, but should I go trough the trouble? Could I use one of 
these for the endcap for my secondary coil? And, would it be okay to use 
metal screws to attach it to my sonotube?
Thanks
Adam