It looks gross, it smells gross but it makes magic. Experiment with liver of sulfur ($16.50) metal jewelry patinas and see how much fun you can have with surface finishing.
Liver of sulfur is a chemical compound that oxidizes the surface of some metals to blacken or darken the metal. Here are some tips to keep in mind.
How to set up – there is not a precise recommended ratio of liver of sulfur per ounce of water, for example. Most metalsmiths have their preferred approximate recipe but generally speaking a tablespoon or so of liquid liver of sulfur per small 8oz crock is plenty. The chemical works best when it is warm or hot so most studios have a small crockpot ($22.47) designated for liver of sulfur. Plug in the crock and heat enough water to cover your piece(s) then fully dissolve liquid or crystal liver of sulfur into the warm water and you are ready to add a jewelry patina. Designate a pair of copper tongs ($8.45) for your patina and pickle station. They will completely blacken in the liver of sulfur. If you choose to use the same tongs for your pickle, you will get large black flakes in the liquid but it will still work just fine.
Use the right metal– liver of sulfur works best on silver and copper. It will not work if the silver has an e-coating, anti-tarnish treatment or a plating finish of fine silver, rhodium or gold. Be sure your metal is clean by using pickle or sandpaper and then rinse. Surface contaminants will cause the metal to resist oxidation and effect results. Brass can sometimes be oxidized but results are highly unpredictable. Plan for more trial and error and be prepared to be patient to get the jewelry patina you want.
Expect variation – Many factors cause variability in oxidation. You will see some patinas take on blue, purple or green highlights. Expect some surprises and you will never be disappointed. Also keep in mind that the larger the surface area the more variation will show. Oxidation is often most effective on textured, stamped or engraved pieces where the whole piece is oxidized and then the surface is polished back to bright or satin which leaves the contrasting dark patina in relief only.
Be safe – while this chemical is a studio mainstay, you should never be cavalier about safety precautions when firing up your crock. Liver of sulfur fumes are harmful to your health and should be avoided. Ensure thorough ventilation – that means much more than a cracked window. The smell is a good indicator of the level of fumes in an area. You may even want to keep your crock outside. Also avoid leaning over your crock and inhaling right above the liquid where fumes are most intense. It is harmless on your skin though it may stain your skin and clothes. See the liver of sulfur MSDS sheet for complete safety details.
Layer it on – timing is tricky to master and will depend on the solution intensity and temperature among other things. The best technique is to submerge your piece for a minute or less and then remove it, rinse in clean water and assess results. Repeat until you achieve the desired level of darkness in your patina. This allows you to examine your work and layer on the oxidation for greater stability. Jewelry patinas achieved after a lengthy continuous bath will often flake off the surface.
Use proper disposal – liver of sulfur can legally go down the drain in most areas as long as it has been neutralized first. That means adding baking soda to the solution until it no longer foams. This may require several rounds of adding baking soda, waiting for foaming to stop and then adding more. It’s messy so make sure you are in a large stainless steel sink that won’t stain. Diluted liver of sulfur is also an excellent garden fertilizer. Some plants love it and the compound is frequently used in commercial fertilizer products. Just make sure the chemical is sufficiently diluted first.