Covering silver wire for use as a speaker cable

Ozzy, don't bother with the pipe foam; been there! It's a nicer color granted, but the split down one side makes it difficult to work with in this application.

Use PTFE Teflon tubing that is at least two gauges larger than the solid silver wire. You want the silver wire to "float" inside of the teflon tubing. Do not use shrink wrap tubing especially if you intend on shrinking it. I would also recommend using at least a 16AWG wire. If your silver wire is not at least 16AWG or thicker, try using copper at about 12AWG-16AWG with PTFE tubing.
The best speaker wire I've ever heard was bare 12AWG copper Romex bought at an ordinary electrical supply house. All of the insulation was stripped off with just bare copper remaining. Keep in mind that this was a mono block setup with only 18" of wire suspended directly from the amps to the speakers. Obviously, proceed with caution and if you have children or pets; forget it!

Willoamp, What about using both silver and copper wire?
This would increase the gauge .

Silver and copper ...

http://www.ultimatecables.com/

Also happens to be why I wouldn't bother making speaker cables.

Why would you be contemplating using silver and copper? If you can afford it, use silver only. It has the highest conductivity.