I'm new to jewelry and I've been practicing my soldering by soldering flat copper wire strips (3mm x 0.76 mm, solid copper) to pennies. I've been using a small butane torch with silver solder. I do clean the surface of both the wire, the pennies and the solder with emery cloth.

My solders LOOK pretty good, and seem pretty tight...however I AM able to pull the wire away from the penny surface with my fingers - with some effort. Its not easy, but I don't have to use plyers. Once I've torn off the wire, the solder does look nice and evenly embedded in both the penny and the wire itself.

So, I guess the question is; how strong should my solder be? Is this a sign I'm not doing it right, or is this just the limits of silver solder under the circumstances.

Thanks!