Soldering gold-filled wire can be accomplished with familiar jewellery-soldering techniques, but a yellow solder is recommended to avoid a harsh contrast with the gold. Most yellow-coloured solders are designed for use with gold or gold-filled pieces---check the label of your yellow solder to be sure. As is the case for most jewellery-making projects, the key to soldering gold-filled wire is good preparation. With the right equipment, you can successfully solder gold-filled wire yourself in just a few minutes.
Soak the gold-filled wire pieces to be soldered in pickling solution. Keep the pieces submerged for 10 minutes, and remove with the tongs. Dry the pieces with a clean cloth.
Paint the areas to be joined with liquid flux and a paintbrush, applying a thin coat to each piece. The flux will remove any oxidation still remaining on the metal after the pickling.
Clamp the jewellery pieces together, using a small clamp or a bit of wire to hold the pieces in place.
Turn on the soldering iron and allow it to heat. While the iron is heating, position the tip of the solder wire at the joint, holding the solder by the spool.
Apply the tip of the soldering iron to the solder until it melts. Guide the solder into the joint with the tip of the soldering iron until the solder has flowed evenly into the entire joint area.
Unplug the soldering iron, and allow the jewellery pieces to cool before unclamping and handling.