Rose weld on a burly seat tube
I once heard that the compressive strength of ice is increased with the addition of sawdust (actually called Pykrete) It turns out that pine needles do a really good job as well: The ice stayed frozen for much longer than normal_ I usually only have a few minutes before the tube starts dripping. The Pinecrete tube didn't seem to drip even ten minutes after bending.
The mixture expanded much less than just straight ice. It normally blows the plugs out by a few inches, but here it didn't seem to change volume at all.
The goal was to make the profile of the bend rounder and it did make for a .5mm difference in diameter.