Large Kiln Shelves, redux

[Eric Baker]

Hey fellow glass clan members,

I know this question has been visited in the past, but some of the responses are dated, and some suppliers mentioned have gone out of business, and/or I'd hoped for more current perspectives on options available.

Essentially, I need a 20 inch x 60 inch kiln shelf that is flat (as much as possible, if not perfect), and won't weigh a thousand pounds.

I've seen Euclids shelves mentioned, and am leaning that direction. But I also worried about the heat sink that would be, plus the difficulties in moving the shelf in and out of the kiln. I figure even with it being extruded, and lighter than a solid mullite shelf, it still won't be pleasant to move in and out of a 15" deep coffin sized kiln.

I currently use some FiberFrax HD 2" boards in the kiln now, one 36" long and the second is 24" (both 20" wide), but the seam is killing me. I've got a heavy, large project that needs to be fused in the coming weeks, and a seam in the middle of the piece won't work at all since this is mostly transparent. Hence the desire for one monolithic shelf. Additionally, my HD board shelves have warped slightly over time, and that won't work with this large piece also.

So basically, I need the perfect, large, light-as-a-feather, excruciatingly flat, warp-proof, crack-proof kiln shelf. I'm not asking for too much. Though, I was hoping for the winning lottery ticket as well... and darn it, I haven't found that one either! Alas!!

[Buttercup]

How do you plan to lift it?

Edit: Oops, missed the 'light-as-a-feather' reference!

I like the HD fibre board. Do they come big enough for your project?

[Eric Baker]

Hi Buttercup!


Unfortunately, my local supplier only stocks the Unifrax HD boards in 24" x 36". To special order a larger board was ridiculously expensive and I'd be stuck with massive quantities of HD board!

P.S. You didn't mention your winning lottery ticket numbers! I'm all ears!

[Brad Walker]

I don't believe a "perfect, large, light-as-a-feather, excruciatingly flat, warp-proof, crack-proof kiln shelf" exists.

The Euclid shelves, or anything similar, will be too heavy to move in and out of the kiln on a regular basis. And they can crack if not fired properly.

Fiber shelves are lighter and aren't a heat sink like the others, but anything that large won't be easy to move in and out of the kiln anyway.

Unifrax does make larger fiber shelves. They're very expensive and probably need to be ordered directly from them. Or it's usually cheaper to have a local distributor special order for you.

No perfect solution, which is probably why the guys who make huge panels just fire on some sort of prepared sand base on the kiln floor.

[Eric Baker]

Thanks, Brad--for crushing my hopes and my dreams!
You didn't even give me the winning lottery numbers!


I'm going to shoot for a Euclid shelf and just leave the big, not-nearly-light-as-a-feather shelf in the kiln for perpetuity.

I hadn't thought about the sand-based idea, though--that's a good tip!


Thanks!

[Brad Walker]

Just be careful with the Euclid shelves. They will crack and they hold lots of heat so expect it to take longer for the kiln to cool.

[Eric Baker]

Oh, that's good info, Brad.


Do you have a recommendation for adjustments to firing schedules? I guess particularly on the ramp up to working temps?

I currently fire on Unifrax HD boards, but they're not big enough for this project. I typically fire up to process temps at around 275 deg. F to 300 deg. F per hour.

I don't crash cool my kilns, but I do let this Paragon, brick-lined, coffin-sized kiln, to cool naturally from 1470 deg F to 900's--usually about 2 hours, which I guess translates to a cooling rate of about 250 deg F per hour. I figure it'll slow down substantially with the added heat sink of the extruded shelves versus my fiber shelves.

In your experienced opinion, are my heat-up and cooling rates too aggressive for the Euclid's? I don't want to crack them, for sure.

[Brad Walker]

My experience is with the Dyson shelves. When that company went out of business, Euclid bought the rights so I assume the shelves are similar, if not the same.

At any rate, Euclid should provide you with a recommended first firing schedule, so make sure to follow that.

I heated up at around 250dph, a bit slower than you, but as long as you're under 300 you should be ok. I never crash cool either, so I think what you do should be fine. You will find that it takes longer to cool than your fiber shelves.

My shelf cracked after 7 or 8 years of use, so it wasn't an immediate problem. And I may have contributed to the crack, I was doing some firing with sand and vermiculite and my guess is that that spot was hotter than other areas of the shelf and that caused the crack. (But that's just a guess.)

After the crack, I switched to fiber - got a big piece from Olympic Kilns, which was cheaper than the Unifrax HD shelves. And I was able to pick it up, saving the shipping.

At any rate, good luck. They're expensive shelves, but if you need the size, you don't have much choice.

[Buttercup]

Hi Buttercup!


Unfortunately, my local supplier only stocks the Unifrax HD boards in 24" x 36". To special order a larger board was ridiculously expensive and I'd be stuck with massive quantities of HD board!

P.S. You didn't mention your winning lottery ticket numbers! I'm all ears!

Try your cats' birthdays. If you're kittiless adopt a couple! Good luck!

[Eric Baker]

Hi Brad,

Thanks for the tips and info; I really appreciate it!



And thanks, Buttercup--I never thought of using our three cats b-day's as lottery numbers.


I'll either be filthy rich, and send you a retainer fee--or I'll be in the doghouse when my wife finds out I spent my retirement on glass (and lottery tickets!)

[Marty]

Bullseye had a tip sheet or some such on fusing large projects (like Jun Kaneko's stuff). It involved lots of mullite shelves bridged with something.
Call them.

I don't have that lottery number either.

[Eric Baker]

Thanks, Marty--I'll check into it...