Sealing secondaries

["Brad DiGiovine" <guido28-at-mediaone-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

To all,
I am currently in the process of building a large coil.  The secondary
form is 8" in diameter and 40 inches long.  I sealed the outside of the
form with urathane twice, wound the coil, and then coated it 4 more
times.  I want to seal the inside of the form, would drying it and
sealing up the ends with great suff foam work well, i was wondering if
the foam would actually have any dampness in it that it may seal into
the cardboard form.

Thanks for your help!
Brad DiGiovine