Place the gold-plated parts of the circuit board into a container. Add two parts hydrochloric acid and one part hydrogen peroxide, which makes a weak 3 percent concentration. Leave the parts soaking for a week, stirring occasionally. The solution darkens, and the gold flakes off.
Pass the liquid through a coffee filter to separate the gold flakes. Gold melts at a temperature of over 1,000 degrees Celsius. Adding borax reduces the temperature to a more manageable level. Heat borax in a heatproof container until it softens, and then add the gold flakes and heat until melted. When cooled, separate the gold from the solidified borax.