Liver of Sulphur
Liver of sulphur is a chemical compound used in metalworking to create antique-looking patinas on silver and copper bearing alloys such as brass, bronze and copper.
The patina process is very simple. You start by mixing up the liver of sulphur with water, then simply dip, soak or paint the solution onto your metal. The solution reacts with the metal and results in either a colorful or darkened patina over the entire surface of the metal. Usually, color is wanted only in recessed areas and not on raised surfaces, so those areas are usually polished, leaving the patina only where desired.
Also google search "How to Create Patina with Liver of Sulphur"
Translation of Japanese Instructions that come with this product is below
How to use the Liver of Sulphur (LoS) liquid
1. Put hot water (about 70 to 80 ° C) in a paper cup, add 2 to 3 drops of the LoS liquid, and stir well.
2. Put into the solution the work you want to color, take it out when it turns black, and wash it well with water.
3. If necessary, polish the convex part of the work with an abrasive.
* Do not use for any purpose other than smoldering.
* Some may crystallize, but there is no problem in using it.