Keum-boo, or Kum-boo, or Kum-bu (pronounced Come-boo) is a Korean technique meaning “attached gold.” It’s also popular in Japanese and Chinese cultures and may also have been used by the Greeks and Romans. So, basically, Keum-boo is when you add 24k gold to the surface of silver. You can attach it to other metals, as well, it’s just most commonly found on silver. It can also be applied to all types of PMC. The technical term for this whole process is diffusion bonding. The metals don’t melt together; the atoms of the two metals are exchanged and bond together.
Keum-boo begins on a hot plate. Yes, like the one you had in your college dorm to heat up Ramen (Sorry, we don’t sell hot plates here at JewelryTools.com, but you can find one at your local retail store). You heat up the hot plate to somewhere between 650 degrees to 850 degrees Fahrenheit, or hot enough that it blackens the tip of a wooden chopstick or Popsicle stick. When it’s up to temperature you place the gold leaf on with tweezers, grab your burnishers and starts pushing the gold into place. Now, if the burnishers get hot, trade them out for cool ones. If you continue using a hot burnisher you run the risk of tearing your gold leaf. Once you have the gold in place you can place the metal or PMC onto a steel bench block to cool it off. The steel block will pull the heat away without damaging the metal or PMC.
Just a few notes before you begin the fun of Keum-boo. A few different sources argued about what type of gold to use in this project. Some say to use gold leaf because it’s thinner and easy to put into place. You have to be careful with gold leaf, however, and place it between two thin pieces of paper, like tracing paper. Then trace a design or cut it out while it’s between the paper. There are experts who don’t like how thin gold leaf is and so they suggest Allcraft KB24, Art Clay or homemade. Rolling your own foil may produce a thicker foil that you’ll enjoy.
Remember I mentioned cutting shapes out of the gold? You can cut shapes using an X-ACTO knife, paper punch, craft knives and most scissors. After all is said and done you may have some burnishing marks left on your work. Cleaning those isn’t too hard. You can get a small amount of pumice damp and, using your finger, give it a light rub. Or use pumice on a soapy brass brush. The same can be done with baking soda instead of pumice, you’ll simply achieve a softer look. Just steer clear of satin finish wheels and other harsh abrasives. If you’d like to learn more about the art of Keum-boo we invite you to pick up Keum-Boo on Silver Techniques for Applying 24k Gold to Silver by Celie Fargo. She’s a wealth of knowledge on the subject and will teach you more than you thought possible.
http://www.youtube.com/watch?v=KBY3dR66b6Q: 1312-4 Mark Nelson Rio Grande Keum-Boo on Beads, Baubles and Jewels
Fargo, Celie (2007) Keum-Boo on Silver Techniques for Appying 24k Gold to Silver.
Hinged Bracelet: http://www.celiefago.com/about_my_work.html
Cuff Bracelet: http://www.liloveve.com/classes/keum-boo