and to provide a flat black inner surface when painted. The
fiberglass went over all this. I even molded on a couple of rings to mount a finder.
Problem came when it was time to take it off the PVC. Even with the wrap and cork it was tight. Huffing and puffing I could move it a little and then it would stick again. Finally got it out with a combination of breaking the brittle PVC, brute force and patience.
The cork-lined fiberglass tube did work pretty well though even though it was only about 5/8 inch larger than the mirror.
If I were doing it again, with sonotube or PVC, I would split the mold tube in half (maybe even thirds) lengthwise and then hold the pieces in place with some wood disks. After the fiberglass has dried, pull out the wood diska and the staves of mold should come out pretty easily.
Tom Clarke