Hi Folks!
I just fired 8 stoneware mugs with cone 6 commercial glaze. I glazed the bottom of the mugs and placed them on stilts. In a few cases, the stilts seemed to have melted. These stilts came with an old kiln and a bunch of other stuff. Are stilts made to different specs, i.e. high fire, low-fire? I really like to glaze the bottom of my tableware. How can I make sure I don't get melted stilts and ruined tableware?
Cheers, Suzan
Ouch. In my experience, if nothing on the stilt package says otherwise, the stilts can start to melt around cone 5.
Generally Stilts are only used in earthenware firings, as Stoneware clays usually soften so much the stilts wind up embedded in the bottom of the pot. You might be able to use metal ones (usually stainless steel) at cone 6, but I wouldn't recommend it. Ceramic stilts are made from fairly low fired clay, so would not survive, even at cone 6.
If you are worried about rough undersides of your pots, rub the pot bottoms together; makes them really smooth, and it's cheaper than using abrasives. I use a pretty sandy clay, and it works a treat.
Steve Bath UK
In article , Suzan writes
Hi suzan, Steve Mills is bang on; bad idea using stilts with anything above 1200 C. I burnish the bottom of my pots after turning them on the wheel, once fired they polish up quite nicely with a little carnuba wax.
I have had good luck with stilts from Rovin Ceramics (my local supplier in SE Michigan, USA). These say in the ad "Can fire to cone 6" and they really do. They are a 3-armed ceramic base with heavy-gage wire points. Nothing about the stilts melts at cone 6, though of course the points do leave indentations in the glaze that you may have to smooth out a bit with a stone afterward.
Whether the wire points are stainless or not is another question. When I wanted cone 6 bead wire a while back, I had a hard time finding out what was what. Buying bulk wire with known composition from industial suppliers like McMaster-Carr, it was hard to tell what temperature it would handle from the specs... they don't really give a good idea of strength at temperature. On the other hand, most bead wire from ceramics suppliers was rated much lower than cone 6, and usually with no composition given. I ended up with 14 gage nichrome from McMaster-Carr, which works passably well as long as the load isn't too great. T316L stainless was much worse (sagged). But the points in the stilts look like a much heavier gage, and they are short so don't tend to bend anyway.
I did make some special stilts of my own by embedding the nichrome in a stoneware base, and they also worked OK as long as the exposed wire was kept short. (1/8 inch or so.)
Best regards,
Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis
First off, I'm way out of my depth here.
But in the spirit of internet communication I'm goin' comment anyway #:0)>
Isn't element wire the perfect wire for stilts? It has to withstand the temperature and retain it's form (though perhaps not the weight at that temp). It should also be available to lots of people from old elements. Cut on an angle it shouldn't make too big stilt marks.
Then I'd be tempted to use the clay used for kiln furniture for the stilt body ... if I knew what that was?
Yeah, I'll shut up now. Sorry.
Bob Masta wrote:
Element wire is OK except that after being fired it goes brittle, so Nichrome wire is better, preferably heavy duty i.e. thicker than 1mm. They've got some 1.8mm at Bath Potters Supplies, and yes, cut at an angle and set in Stoneware clay they would hold up well, but as I said before I would not recommend it above cone 6.
By the way I've retired from the company above now, but I'm still loosely associated with them while the new owners get up to speed.
Steve Bath UK
In article , pbhj writes
i thought element wire was nichrome.
when hot, it is pretty soft.
Happy retirement ..!
Nichrome (80% nickel, 20% chrome) is rated for 1200C as an element, but doesn't deform when hot. Or at least, not as much as standard element wire, which is Kanthal (FeCrAl, various grades). Kanthal elements are good for 1400C, but deform a lot and thus need a lot of support (element grooves, for example).
Cone 6 is around 1200C (depending on how fast the temperature rise is). I do get some sagging of my nichrome bead wires at cone 6, depending on wire thickness and load. Since I have read that Kanthal is supposed to be worse, I haven't tried it. (I use silicon carbide rods as heating elements, so I don't have a ready source of element wire. The only Kanthal wire I had access to was a really small gage.)
Best regards,
Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis
Some are, but they don't have the capability of working at + 1250oC see:
The most commonly used kiln element wire in the UK is Kanthal A1 which has a Max. continuous operating temperature of 1400oC (2550 F).
75.52 percent of its makeup is iron, the remaining 24.48 is a mixture of Carbon, Silica, Molybdenum, Chrome, and Aluminium. It lasts really well in a kiln, but gets very brittle when cold after being fired.I'm not a scientific type, I'm just curious, and just wanted to find out what elements are made of. There's a lot of information out there!
Steve Bath UK
In article , Charles Spitzer writes
Bob, make some solid cones out of coarse clay, stick 2 inch plus bits of Nichrome wire into them all over like a Christmas tree, bisque fire and use them instead of the *washing line* technique for your beads; no sag, take up less space, and easy handling in and out of the kiln.
Steve Bath UK
In article , Bob Masta writes
Steve, I use the "washing line" method because many of my "beads" are decidedly non-standard, some up to 3 inches long. These are the ones that cause the bending problems. Luckily, I am also using large threading holes in these, so there is room to stick 3 of my
14-gage wires through. That pretty much does the job, but I have been thinking about ways to make these large beads lighter anyway, for the benefit of the wearers if nothing else!Best regards,
Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis
bob - mix saw dust into the clay. i've been doing this lately. *chip* sawdust, like pet bedding, leaves a neat texture. but i doubt this would be useful for beads.
"milk" saw dust, the suuper EXTRA FINE you get from a vacuum draw at the sanding machines (and actually swirls around in a bucket like milk) leaves little actual evidence - but does lighten the pieces. THIS would likely work with beads.
~ besides, after a glaze i don't see a problem?
or, get carried away with TOO much saw dust blend and maybe you'll get a cavernous affect from so much dust being burned off? i haven't tried that yet, but will soon. i also want to try chunks of wood & see what results. nooks & cranies left over from a fire would be a fun affect.
see ya
steve
Steve, I've been thinking along these lines, and am encouraged by your success. One idea I'm toying with is to use a lot of filler like sawdust, maybe even rather coarse, and then dip in slip to get a nice smooth outer surface. This is on the back burner at the moment, but I'll report here if I come up with anything good.
Best regards,
Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis
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