FUSING SILVER & GOLD
Keum-boo is a Korean technique where a very thin layer of gold is being fused to the surface of fine silver. This technique cannot be compared to soldering, because the gold does not melt on to the silver. It is fused due to heat and pressure.
You will need gold leaf to perform this technique. I bought 23 karat gold leaf at a painters supply store. The gold leaf is very thin and it will deform or tear easily. So handle it with care. Make sure not to touch it with your hands. You don’t want oil or grease from your fingers to transfer to the gold leaf. You can use trace paper or the paper the gold leaf came in to hold and cut it. In my video I will show you how you can do so.
As stated the with the Keum-boo technique a thin layer of gold is being fused to fine silver. In my tutorial however I am using sterling silver. To make sure the gold will really attach to the silver it is important to make sure that the surface is completely free of oxidation. To do so we are going to bring the fine silver from within the sterling silver to the surface. You can do so by annealing, quenching and pickling your sterling silver several times. When you are left with an even matte and white finish you have received the result you are looking for. Make sure not to touch the part where you want to add your gold layer to with your hands. Again, preventing grease or oil from your hands to contaminate your piece.
You can use a hot plate to heat up your piece. So whenever you are ready, place your silver piece on the hotplate. Let it heat up and you will know that it’s ready for adding the gold when you will add a tiny drop of water on there and it will start sizzling. Another known technique is to take a wooden stick or dowel and hold it on your silver. If it turns dark and starts smoking your piece will be hot enough to proceed.
When your silver has reached the desired temperature, very carefully place the gold leaf on there. Don’t rub it (you don’t want it to tear), gently press it down. If the silver is the correct temperature the gold leaf will stick to the silver.
And then it all comes down to burnishing. For burnishing you can use a steel or agate burnisher. Which ever one you use, make sure your burnisher has a high gloss polished surface. Some people prefer an agate burnisher because this is a bit more gentle and will leave fewer marks. Hold your piece in place with a pair of tweezers or something else and gently burnish it. While burnishing make sure that your burnisher doesn’t heat up. It will stick to your leaf gold and you can undo your work. So gently move forward until you see a nice and shiny gold surface appearing. You can clearly see when the gold attaches to the silver. When your piece has the correct temperature burnishing is almost effortless.
When the gold leaf and silver have fused you can take your piece of the hotplate. Don’t quench it because this can undo the bonding process. Just let it cool by air. When your piece has cooled down you can remove access gold leaf if necessary (the parts that you didn’t burnish down can be taken away with a brush) and give your piece a polish. Or, of course, another finish.
Some final tips:
Apply Keum-Boo when you are done working on your piece. You can solder after using this technique, but chances are you will get some blisters or little bubbles underneath your gold layer. So avoiding this feels like the way to go for me.
Silver, gold leaf and patina are a way to go. Darkening the silver will really bring out the gold. It’s not mandatory, but when handing out tips, I can’t skip this one.