On Mon, 8 Nov 2004 22:38:49 +1100, "J. Dent"
wrote:

How is this done?

If it's net and deliberate, usually a black-tinted filled epoxy.
There are a few glues that will give a black line anyway (just look at
some plywood) but to give a deliberate one, epoxy is the favourite.
You can fill it and colour it (artist's acrylics) without distrubing
the glue strength.

--
Smert' spamionam