Adventures with an Ultralite Kiln – Keum-Boo
Oh my, but I love this new toy, oops – tool
Let me count the ways, as I believe Shakespeare may once have written (warning – here any resemblance to fine writing endeth)
First. I can anneal bits of silver without a flame. Perfect for beaten jump rings, for regular ring resizing, softening work hardened wire or sheet before sawing / whilst dapping. Particularly fabulous for those items I have already soldered, and don’t want to melt the solder.
Second. I can fire silver clay in it, without having to clear the kitchen hob, so I can multi-task during jam season.
Third. Keum-Boo with no risk of scorching my eyebrows orf from the naked gas hob
Fourth. I’m assured I can do tiny bits of slumped or fused glass with it
Fifth. I’m also assured I will be able to do small bits of enamelling with it
Finally (so far) I can do all this at my desk, upstairs, sitting down, and it will heat the room for me. And, I can do all this safely, using the electricity we generate through the PV cells on our roof, effectively meaning it is free and carbon neutral. SMUG FACTOR!!
I’ve been able to find very little useful information about how to use the Ultralite, unfortunately, so I thought I would log everything I learn here, in case anyone else is trying to suss theirs out. I’ve done quite bit of silver clay firing now and have learned some useful things- (there was only a minimal amount of melt!)
However – I’m not an expert at any of this, by any means. It’s trial and error with me, but I love to see other people’s tutorials and goes at things. If you are thinking about an Ultralite, or just wanted to know how this was made, this is for you.
So. Today I did some Keum-Boo trials.
I’d researched this using the internet, and this, in summary, is what I found out. Keum-Boo is traditional and ancient Korean technique, where gold is bonded at a molecular level to fine (aka pure 99.9) silver using heat and pressure only. The literature I found says you can do this with sterling silver (if you deplete the copper from it) and also with other metals.
You could use a blow torch, or a hob, an open fire or a commercial hotplate. Or of course a (drum roll) kiln. Anything that will take the temperature of the silver to 840 oC, ideally holding it there steadily because it’s important to be precise with the temperature – too cool and the gold won’t bond fully; too hot and it will be absorbed fully by the silver. I’ve tried this with my gas hob, and also with a blow torch. Both were a bit of a struggle and I also felt that hovering closely over a naked flame wasn’t the safest of options!
This is one of 3 items I completed in this way, back in 2014, which was a cupcake for a charm bracelet. I’d also made a couple of pairs of studs, one of which was a leaving gift for one of my colleagues. All the others I managed to overheat and the gold sank into the silver.
I felt so nervous poking away with my agate at something tiny over a roaring flame, and it took so long for a – mostly – unsatisfactory result, I decided just not to attempt any more. Then I stumbled across this YouTube video of Celie Fago using an Ultralite and my 3 reasons rule was fulfilled. 😀 (see Make it count…)
I figured once I reached £1k profit, I could justify purchasing one of these, and started pricing them. Then, I lucked out and found one with all I needed (plus stuff I don’t, of course!) on Ebay
I can’t be arsed with depleting sterling silver (I’ve always been a bit lazy, loving my short cuts)
so I thought I would try using 0.3 fine silver sheet that I had bought from my regular bullion dealer, intending to use it for bezel setting these lovelies……………..⇒
and also on some fired Art Clay Silver charms I’d made – a couple fully polished and a couple that were unpolished and unbrushed. This is because one of the articles I found talking about this suggested it would be easier to apply the gold to the clay if it hadn’t been brushed.
I can’t abide waste, and I’m terribly impatient, so even though I’m effectively making myself a sampler, I thought I’d try for a pair of drop earrings at the same time. I’d also read about using crafting stamps to cut shapes out of the gold foil / leaf and applying it.
I used my magic disc cutter I may have mentioned a few times already (!) to whack out a couple of medium discs, filed the edges and then domed them. Then I got out my gold….
I studied bookbinding and paper conservation at college back at the beginning of the 1990s, and because I loved the process (and it was so flippin’ expensive), I have kept all my tools and kit. It’s been in storage a few times, moved house many times, and now it’s in the loft. HA! Hoarding vindicated!!
What you can see in the first photo montage is the magic disc cutter and my pair of cut 999 discs; my gold leafing setup – a special cutting board and windbreak I made back in the day and my gilders knife; the handbeaten book of gold leaf that cost me the equivalent of 1 weeks rent in 1992 (that’s not kept up with inflation – I assume because they are no longer hand beaten); and a sheet of 24carat gold from the book, folded over multiple times and put between tracing paper.[*] I’ve then punched out a couple of pieces of the gold.
Folding it over wasn’t an exact science, I guess it’s now about 8-10 times thicker than the original leaf, which was very, very thin. I did this, because everything I read said to use thicker gold foil, rather than leaf (but that is the only difference between the two, the thickness)
Whilst I did this my lovely Kiln (I must think of a name for it) was heating up, with the copper disc on the top, and the lid above that to speed up the heating. I used the disc with the dome in it as a number of the items I wanted to apply the gold to were curved.
I got a clean artists paint brush, licked it (sorry if that sounds a bit gross – that’s what all the research said to do, and it fit with my bookbinding training!) and dampened the inside of the curved discs. Then I laid the cut piece of gold leaf on to the discs, and placed the first layered disc on the copper sheet that’s acting as a lid to the kiln.
I learned from this, that
the gold needs to be really well smooshed together and
if precision is needed, lay the gold on the silver whilst it is OFF the kiln and
it’s worth getting the silver quite damp if there is detail in the cut out.
The first disc worked really well, but the second dried out whilst I positioned the first and the layers of insufficiently squished gold separated. Fortunately because I didn’t have it on the kiln, I was able to whisk it off, and use it on the other items.
In this second montage, you can see the gold laying on the silver domed discs on the left ready for the heating process (this is where the lower one dried out, and the layers separated when I lifted the top layer of tracing paper off) In the centre photo, you can see how it looks whilst rubbing the gold to the silver on the brass plate, and in the photo on the right, you can see the completed disc.
The actual Keum-Boo process is very basic. Simply place the silver on the hot brass disc on top of the kiln. If the silver is already up to temperature when the gold is placed on it you can actually see it cling and fuse – a bit like sequins and static, or when you put cling wrap over a hot bowl. Then, use a burnisher (steel or agate, each with it’s pros and cons) to gently tap on sections of the gold to ensure it’s anchored, before rubbing the gold to the silver. Failing to tap sufficiently will allow the gold to shift, even if you are holding your breath with excitement, as I was 😉
Once it’s all safely fused, either leave it to cool naturally, or quench it.
I wondered if I would be able to see when it was fully fused (it was really hard to tell this using a torch) but it turns out that it is one of those indescribably beautiful moments in nature and alchemy when you can. Next time I might try and video this stage; I didn’t expect it to be so dramatic and obvious.
I repeated this process on the silver clay pieces; I had a couple of flowers with silver clay balls in the centre that I wanted to pick out in gold as I knew from my studs that was beautifully effective and subtle; a charm I had made as a test piece, having made a cookie cutter style mould of a cherub that was smooth clay and the back of a charm that I had impressed with a skeleton leaf as I wanted to see what sort of depth the gold would get to – would it leave the crevices or fill them, or would it fuse evenly allowing all the texture to remain? I also had a random flower, that I thought might work with a ‘splodge’ of gold, before attaching to something with a headpin and a bead
These photos show the tiny crumbs of layered gold prior to fusing, on the brass disc; all the pieces quenching after the bonding, then before polishing and finally after 50 minutes in my barrel polisher.
I only have one agate burnisher at the moment; one termed ‘knife’ shape. It works really well for burnishing silver clay, and it worked fine for all my pieces that were flat or convex, but it was a challenge for the concave pieces. you can see all these little marks on the disc; they look like scratches, and are made as a result of only being able to get the point of the burnisher in. They vanished when I polished the piece up, although using my lens I think perhaps I may have pushed through some of the gold. So. more and varied agate burnishers are now on my shopping list
The pieces that were unbrushed – the flower with the dimples in the petals and the oval pebble charm – were incredibly easy to apply the gold. It tacked on really quickly and evenly. The gold in the flower is only 3 layers thick, but the difference isn’t noticeable, even with my lens
You can probably also see, in the quenching photo; I managed to get the gold to places other than the target areas. I would like to say that this was a purposeful error, to test how easy it would be to remove it – but as I said – I’m very lazy!
As it happens, the flower with the streak of extra gold, was gold that just moved onto the petal by accident; it didn’t tack to the ball fully, so drifted off. (I’d not left the charm on the kiln for long enough). I carefully tried to ignore it, and hoped it would either come off when I wire brushed or when I barrel polished the piece. I thought the same thing would probably apply to the overhang of the gold on the cherub, and yes, this was the case. All these pieces were brass brushed with light soapy water, before I tumbled them using stainless shot.
I’ve patinated some of these pieces, because I wanted to see the contrast. I’ve applied Renaissance Wax to all of them as a light protective layer over the gold even thought it appears to be very durable. The oxidisation on the discs was unexpected, as fine silver doesn’t usually oxidise on heating, but I removed it and then used liver of sulphur to apply a more aged and interesting patina. Rubbish extreme close up photos at the end of this article.(It’s still raining here in Exeter!)
So. what have I learned from this, my first attempt using the kiln?
As always, prep is everything. Have everything to hand
Work in a draught free area. This means factoring in staying at your station for an hour or so, so get your drink, take your comfort break, keep your phone within reach.
If using one of these Ultralites, set it up so that the ‘window’ is away from your dominant hand (it was a cold January day here, so the mild toasting mine got was very welcome on this occasion, however I’m delighted to report that my eyebrows remain intact)
Make sure all your tools are clean and grease free – gold loves grease as much as I love wine; if you rub your skin lightly and touch a tool, there will be enough oil transference for the gold to adhere to the tool. Great if tooling a leather bound book, not so much for this.
Don’t bother finishing your silver clay; leave it unbrushed after it’s firing / soldering, but do make sure that all soldering is completed and any pickling done should there be any firescale on an area you want to apply the gold before starting.
I think I may need to buy something with a hole in it / try some kiln fibre, or drill a hole in one of my brass sheets for earwires to poke through
clean up any fine silver sheet really well, and degrease it prior to the application of the gold
Essential tools are
fine tweezers for moving the gold leaf. Mine are reverse lock paper-cutting tweezers with incredibly delicate points. Make sure they are grease free.
something on which to cut your gold. My gilder’s block is simply natural suede, laid over a piece of blanket, nailed round the edge with upholstery tacks. It’s then been liberally dusted with ground chalk (talc or gypsum will do if you can find it in a pure form)
you could just tear or cut all your gold with fine scissors, or of course punches, but having a block like this made it easy for me to fold and smoosh the leaf into a thicker layer. It was the work of moments and a massive financial saving. I used the same kind of motion as when prepping ink for lino printing, or reconstituting silver clay
gold cutting implements. Punches / fine scissors / knife. Mine is a gilder’s knife, but any traditional style unserrated knife will work as long as it’s not terribly sharp and clean
So. that’s it. What I learned from my first Kiln Keum-Boo. I am very, very happy with my purchase. Next up, might be a mini post on annealing with it, and firing ACS.
As I said above – I’m not an expert at any of this, by any means. It’s trial and error with me, but, if you have a question do send it to me via the comments. I’ll share my thoughts – for whatever they may be worth!
[*] When tooling leather bindings in gold, the principle is to build up the layers of gold leaf, resulting in a deeper and more durable finish – think French polish, rather than polyurethane. The foil sold designated as suitable for Keum-Boo is described as 24 times the thickness of leaf contained in the gold leaf books – these tend to have 24 sheets. This would suggest that it should be the equivalent price of the book, as although it will have fewer customers, it’ll take less work. As it happens, it’s nearly 3 times the price of the book (in the jewellery bullion dealer – the books of leaf are cheaper from art / bookbinding suppliers), so I think I’ll continue folding my sheets over and over!