Prometheus wrote:

I've done it with a bit of wood. Just take something that is really
hard, like maple or mesquite and chisel, grind, or whatever at it
until you have a thin tip. Use that to burn the inside- it will burn
your "tool" as well, but something like that is easy to replace.

I'd go with either of these before sticking a metal contraption into
the bowl- granted, that's how you made the bowl in the first place,
but a bowl gouge and a penny in a pair of vise grips are not the same
animal.


This is exactly right, except I would want a wide slice of hardwood so
as to generate enough heat without risking tear from a thin "tip".

Cut a thin slice of hardwood on your bandsaw, at least 2" wide.
Try to form the end (yes, end - across the fibers)to the same curve as
the inside of the bowl and start with a light pressure, then harder
and harder as the groove deepens and smoke develops.

If the bowl is not _exactly_ round, don't do it.
Outside burning with a wire is forgiving as to uneven curve,
inside burning with a hard medium is not.

BjarteR