The Grand River Bead Society had a wire wrapping class last fall. What intrigued me was what the instructor used to patinate the final copper pieces. She didn't use liver of sulfur which is arguably the most common product used to darken the color of popular jewelry metals. She used Gun Blue which has one huge advantage over liver of sulfur - no stinky smell!
What is Gun Blue? Gun Blue is used for "bluing" - anti-rust touch up on the finish of guns. Gun Blue may not be easily available in countries with strict gun control. For Canadians, the hunting section of Canadian Tire will have it. Otherwise check the useful links below for some of the dozens of "recipes" and alternatives. (If you are going for the boiled eggs method - remember whole eggs or whites. Not yolks). Gun Blue just happens to be a convenient copper sulphate solution. It also contains selenium dioxide and hydrochloric acid.
What is Liver of Sulfur (LOS) Liver of sulfur is mostly potassium sulphide. When the solid form is mixed with water, a smelly gas (like rotten eggs) called hydrogen sulfide is released.The gas is poisonous in large amounts so it should be used with adequate ventilation.
Also be careful not to get either solution on your skin. Wear gloves if necessary. Keep safely stored away from children and pets. Before you freak out, keep things in perspective. There are other nasty compounds around the house we have to be careful about too - bleach and ammonia, another noxious gas, are two examples.
Comparative Experiments The instructor happened to mention Gun Blue does not work with sterling silver. Intrigued, I decided to check out the reaction with different jewelry metals. I may be a retired scientist but it doesn't mean I can't still do some experiments!
I didn't fancy working with liver of sulfur outdoors in the middle of winter so I used it carefully in my workroom which is a fair size room ie not a closet. The gas disperses very quickly in larger spaces.
Gun Blue comes in small bottles of 60 mL each. I used 2 bottles in a small glass jar.
I heated about the same amount of water in another similar jar - about 45 secs on high in the microwave. (Hot solutions hasten the patination). Only after that did I drop in a tiny pellet of the solid liver of sulfur. I closed the lid immediately and swirled the bottle to dissolve the pellet. Note that I used a plastic spoon to fish out a small pellet from the bottom of the container. Plastic tweezers are fine too. Just not anything metal unless you want to patinate that too!
You're probably saying -
"What about the metal lids of the jars?" I used lids which are coated on the inside so the metal didn't react with the solutions. Acidic foods like salsa are sold in such jars for that reason. I made hooks using coated copper wire which also doesn't react with the solutions. Alternatively, use plastic tweezers. I also kept the lid of the LOS solution closed as much as possible and worked at arm's length. I didn't really smell anything except for a faint whiff or two.
I made several wire coils of each metal which were successively dunked into the solutions for approximately 5 seconds each. Each coil was rinsed right after in a bowl of water close by and placed on paper towels to dry. (Note : Might be a good idea to thoroughly clean the metal beforehand to degrease it otherwise, you might get patchy patination)
Gun Blue turned copper, brass (copper-zinc alloy) and bronze (copper- tin alloy) very quickly to black - faster than the LOS solution. 5 seconds is too much so I recommend dipping these metals in Gun Blue for less than 5 seconds so they won't get so black.
I have to say that the LOS treatment for brass looks lovely.
The characteristic color of
verdigris can be seen with the LOS treatment of bronze.
Gun Blue did work somewhat on sterling silver but not as well as with LOS.
I took the sterling silver coil dipped in Gun Blue and re-dipped it this time leaving it in for a few mintues. Lo and behold! It did darken.
LOS failed to patinate bright aluminum but Gun Blue did darken it.
Storage and Disposal Dispose of the rinse water down the drain with lots of water. Just keep the Gun Blue stored in a safe place wrapped in foil until the next time you use it. The foil will keep light out and lengthen its useful life. Top up as needed. Glass containers are better than plastic as there may be interaction with the plastic. Anyone who works in a lab would recognize these two tips.
LOS doesn't last - it decomposes very quickly with time and exposure to the air and light. The LOS solution I made is a bit murky because my LOS supply is old but it was still workable. You can reuse the LOS solution for as long as it has that chartreuse color - only a few days at most. Just make sure you screw on the lid tight and cover the jar with foil like for the Gun Blue. I am leery of reheating LOS solutions in the microwave - not good to accidentally bring it to boil. So if you really want to reuse it, I recommend standing the closed jar in a bowl of hot water (swirl the jar occasionally) to warm it up.
I don't often patinate so I find it better to just make up a fresh solution every time. After you are done with the LOS solution, leave it around in the closed jar and it will soon go milky white as below. There is no longer any smell when the jar is opened. Just add more water and pour it down the drain with lots of water from the tap.
Some people actually pour their LOS solution in the garden. I think they may be confusing potassium sulphide (LOS) with potassium sulphate (fertilizer). Two different chemicals entirely! Gardeners do use LOS but in fungicidal sprays.
So What's In It for Me? No animals or humans were harmed in the experiments with Gun Blue. So I must say I do like the non-violent association with the use of this chemical.
Gun Blue is a lot more convenient compared to handling LOS and has no ghastly smell. Works very fast too without any heat. For people who do not patinate often, Gun Blue is a better alternative as there won't be any waste. Most of my LOS supply is going to go off soon and will be next to useless!
Some artisans like to use more dilute LOS solutions so they can obtain the right darkness of patination they want with repeated dunking and rinsing.The trick with Gun Blue is not to dilute but to time the exposure of the metal to it. Just a few seconds for copper, brass and bronze but a few minutes or more is needed for sterling silver.
The differential reaction to Gun Blue was exploited in my People Earrings (an affectionate couple!)
now in my shop. I used brass wire and wrapped with sterling silver. I dipped
only for a few seconds in Gun Blue. This didn't do much to the sterling silver but the brass turned dark. Some light buffing with #0000 steel wool brought up the color of vintage brass.
I also deliberately used coated copper wire for the wrapping part for this turquoise with antiqued copper pendant necklace. The coated copper makes for a bright contrast with the patinated copper as it didn't turn dark. It is best to be careful with porous gemstones but the turquoise survived the quick dunk!
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