Sunday, February 21, 2010

Keum boo-hoo

I love the deep and warm luster of gold. Especially high carat gold is so wonderful! I don't however like the price of it. So, what to do, when you want the warmth and sumptuousness of gold and don't have the bucks to pay for it? You gold-plate. But I don't like that. To me it's fake. It's turning silver (or brass for that matter) into something that is designed to look as if it's gold and I really dislike fakes. Leather, stone, wood, metal -whatever, just be the real thing and don't hide what you are. Plastic is a honest material, as long as it doesn't try to look as if it's something else.

But I'm ranting. I was talking about gold. My solution to the thoughts above is to either introduce limited amounts of gold in balls or wires or to partly gild the silver. usually you would use gold leaf and glue it on, but here I again dislike the notion. I want my jewelry to last. Sure it will acquire patina and a few scratches, but II hate the idea of gluing on something, that might come off again a tad too quickly. The solution was keum boo.

Keum boo is a gilding technique said to be invented in Korea, but used through out asia to decorate metallic objects. Here is the recipe:

1) Depleat silver until the surface consistst of only fine silver by repeatedly heating and quenching.
2) heat up the item to be gilded
3) Apply the gold while pressuring it down with a burnisher

Okaythen, I thought. How hard can this be? So I bought some gold leaf (most references said gold foil, but hey -isn't that roughly the same?) and got a small hot plate and I was ready and threw myself into creating a lovely flower for a pendant and "depleated" it thoroughly (most joints re-opened as I heated the piece thoroughly to almost orange). And off to applying, using my torch to heat it up.

Well, first of all, gold leaf is horrible to work with! It's so lightweight and thin, that you can barely breathe when working with it. The heat from the piece made it virtually impossible to force the leaf down onto the surface! I swore and remembered to have heard that some ancient japanese nobles committed suicide by inhaling flakes of gold leaf, which attached itself to the inside of the lungs, hence suffocating the rich man to death -so much more neat and luxurious a death than seppuku, if you feel inclined to go that way...

Anyways - the gold didn't stick very well at all (perhaps I shouldn't have made a coarse surface either) and after 4 layers, I thought that it was okay.

Then I realized I had to make another joint and soldered -bye-bye gold! It almost vanished! Argh!

So I applied another 2 layers, by now quite tired of the whole thing, and when it  still didn't work, I ended up gluing it on. Damn. Not what I wanted. The pendant came out nicely, but i didn't like to put it on sale because of the involved glue.

So, back to research. I now found a number of more specific articles online, the best being the one from the Jewelry Artist

What I learned was:
1) Gold FOIL is necessary! You have to be able to actually cut it with a knife or scissors. So  found a supplier and ordered 10x10 cm of 24 carat gold foil
2) When depleating, it's only necessary to heat until the piece turns dark before quenching and brushing with a brass brush. When the piece doesn't turn dark anymore, it's ready.
3) Have every part cut beforehand
4) Use a hot plate and put the item to be gilded on a sheet of brass or copper and then on the hot plate

So, here we go again, this time a bit simpler: a pair of FLAT earrings!

Here's the gold foil

Here I've cut it out through protective paper

Here they are on the copper sheet ready to be heated

Success! The stuff sticks! A bit hard not to scratch it with the burnisher though, but it's nice!

I engraved some patterns AFTER the keum boo process

After oxydization and finishing, this is what they look like:

More pictures here. I'm happy. It was a tough ride and I was very frustrated, but now I know (roughly) how to work with this technique and will definitely do it again!


  1. Great work Karin! After you finished applying the gold foil, is it very delicate ? Can it with take tumbling or a brushed finish ?

  2. OK LOVED this post (and the earrings of course) and your take on glue and all things imitation is a mirror of my own, but the very thought of touching $GOLD$ makes me weak in the knees. Can you come to my house and show me in person? PLEeeeeaaase? With a cherry on top?

  3. Oh yeah, questions! How did the gold foil react to soldering or did you complete all soldering before attaching the gold? Did you use your torch and the burnisher or did the heat come from the hot plate? How hot does it need to get for the magic to happen, annealing temp? Whats the difference between depleting and recticulation? Do you need to have a prepolish surface on the silver or what?

    SAID I have questions :D Hope you don't mind, it's just that I'm not that crazy about most mixed metals for my own personal designs, but the things you do with gold and silver make my heart go pitter patter, lol. I would seriously like to learn that.

  4. *laugh* so many questions!
    I can't answer them all, because, as you know from the article, this was my first and second try, but here goes:
    1) I don't know if it's delicate, because I didn't dare to test it! I don't think that it would be able to take more than the lightest brushing - unless you want the effect of part gold, part silver of cause. Perhaps it could stand 30 min of tumbling, since you actually burnish it quite a bit after the heat-process.
    2)Clarity - I'd love to come and show you, but I'm afraid it will be a tad expensive ;-)
    3)I didn't solder the second time (first was a disaster when I tried, but then again, that was leaf and not foil), but according to the Jewelry Artist article (link in the article above), it should definitely be possible to solder afterwards, though I have read other places that it’s not recommended.
    3) I used the hotplate for the heat, simply because I was lacking a hand (need to grow a third one of these days…)
    4) I think I had the hotplate on almost maximum, which still leaves the silver looking silvery (as in not red at all). Basically I just let it heat until the gold stuck
    5) reticulation is when the surface ends up being uneven. Depleation is just forcing the copper to the surface (that’s what happens when you heat the item- it turns dark because of the copper)- By pickling you remove that copper. When you repeat that process until it doesn’t turn dark any longer, you know that the surface left is pure fine silver – that’s when you move on.
    6) I brushed the surface with a soft brass brush, but no more than that. It’s important that it’s VERY clean (don’t touch it!) after the last pickling (so the Jewelry Artist)

    I hope that helped a bit - remember, I only did this twice- one successfully, so I can't be more than the one-eyed king here ;-)

  5. Oh you're just so pretty, VERY helpful! Thank you thank you thank you...I'm abolutely going to do this eventually if I ever get rich. One 3 inch sheet of foil is like $60 at rio, OUCH!

  6. Awesome post Karin! Maybe someday (when I sell EVERYTHING from my shop) I'll be able to afford to try this!

  7. Properly-done, the gold foil should adhere permanently - I use a polishing wheel with rouge (quickly!) on mine, and often wire brush the surrounding silver to create a matte surface (contrasts with the gold). I chuckled in recognition when I read about your earlier efforts!