In some recent email side-conversations, I've mentioned a little
trick I use while finishing body tubes, and several folks have said
they thought it was useful, so I thought I'd post it to the full
Problem: You fill small defects (esp: spiral grooves) in a body tube,
prime it, sand it, reprime it, resand it. It looks great. Then you
shoot your gloss finish coat and -- Yuk! -- several of those pesky
little spots pop back into view.
Solution: The problem is that the flat surface of the primer makes
the imperfections very hard to see. To fix this, buff the primer
with fine (#0000) steel wool. This gives the whole surface a modest
shine, even down inside the grooves, etc. Now sand with fine (e.g.
400 grit) sandpaper. The sandpaper is not flexible enough to get
down into the imperfections, so they remain shiny (and therefore
visible) until you have really sanded them completely smooth.
I've been using this little trick for a while now, and it really
does make tube grooves disappear reliably and completely. Maybe it's
a known technique, but I haven't seen it described anywhere, so I
thought I'd pass it along.
Remember to wear a dust mask when using the fine steel wool, since
it fills the air with "steel lint".