Solder, which is used to bond pieces of metal together, is generally supposed to be permanent. However, you may wish to separate two pieces of soldered metal, whether to restore an old piece of jewellery or to correct a damaged part. Removing solder can sometimes be tricky, and methods range from physical chipping and filing to chemical treatment. Older gold jewellery pieces are often soldered with lead solder, which must be chemically removed to avoid damaging the surface of the gold piece. File and sand down as much of the solder as you can without touching the surface of your gold piece. This will make the chemical removal of the rest of the solder slightly easier. Fill a cooking pan with water, and place it on top of a hotplate. Put on a pair of safety goggles and a vapour respirator. Prepare a solution of 50 per cent water and 50 per cent hydrochloric acid. Put the solution in a small Pyrex or other heatproof container. Place the Pyrex container in your cooking pan. Turn on the hotplate and wait until the acid solution begins to steam. Put your gold piece into the Pyrex container, submerging it completely. Turn off the hotplate. Let the gold piece sit in the acid solution for 12 hours. Remove the gold piece from the acid solution. Rinse it in water. Make a paste from water and baking soda, and rub it all over your gold piece to neutralise the acid. Rinse the paste from the gold piece. Pour your hydrochloric acid solution into a jug for storage.- Work outdoors or under a ventilation hood, as hydrochloric acid gives off toxic, poisonous fumes. Avoid contact with the acid.- Follow all fire safety precautions with the hotplate. - Do not use a metal container to heat your acid solution, as the metal will react with the acid.