Pickling is generally used to remove surplus flux, heat discolouration and oxidation from gold and silver articles that have been soldered or been subject to excessive heat.
Sulphuric acid performs the best for pickling, diluted to between 5% and 20%. Add the required amount to cold water very slowly. Either use plastic or brass tweezers or tongs or hang the articles to be pickled in the solution for 1-5 minutes. Wash all articles well in water before handling.
IMPORTANT. Heat is generated by mixing acid and water, so ALWAYS add the acid to the water never the reverse. Always wear protective clothing and glasses/goggles for safety.
As an alternative to sulphuric acid, you can use Safety Pickle. This process although slower, is safer and preferable for beginners or in an environment where young people may be present. Simply mix the required amount of safety pickle with water at a ratio of 200 grams per litre of water. The remaining pickle can then be stored safely in its dry form.