There are several ways to work harden wire, including stretching,
hammering, and twisting with a pin vise. If you are using the wire
to make ear wires, though, is it really necessary to anneal the
wire? Unless you are soldering the wires to the backs of your
earrings, and the annealing is a secondary outcome of that process,
you should be able to sidestep this problem by not annealing the
wire in the first place. If the wire is being annealed as a result
of soldering, you might want to browse the Orchid archives- there
was a fairly extensive thread on this a few weeks ago.
Hope this helps!
Dos Manos Jewelry