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hanee

Self-reliant alternative to buying kiln shelves? Historical approaches?

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As I get towards building my first wood-fired kiln I'm undergoing a bit of both sticker shock and "dependency-shock" with the recommended kiln shelves. I.e. they are both ridiculously expensive and dependent on substantially sophisticated manufacturing processes and materials.

First of all, does anyone know what, historically, was used for kiln shelves? If I was going to fire a terracotta in 1650 italy, would there be such a thing as a kiln shelf and if so what would it be made of? My assumption is that works were just loose stacked, as in pit firing. Or, if not that, then simply stacked and supported with odds and ends of pre-fired work. If so, then what makes such high tech kiln shelves necessary then, today, when I am trying to do something as low-tech as wood firing?

Does it have to do with current approaches to glazing (my sculptures are unglazed, so no issues there)? Or perhaps does it have to do with vitrified wares cementing to eachother (I'm firing terracotta below vitrification, so maybe no issue there)? Or -- perhaps it is just our modern intolerance of the occasional catastrophic failure (a work low-down in the stack coming apart and those above it crashing down)?

Keep in mind my work is irregular shapes to begin with, I'm not looking to stack and fire a set of pots but a bunch of human figures in various poses with out-streched limbs and such. Perhaps kiln shelves are less needed in that case as well (as compared to, say, just some stacked bricks intelligently arranged to support each figure in key places).

And finally, if kiln shelves are an absolute necessity for a wood-fired kiln, could I conceivably make them myself, whether with low-tech materials or modern refractories? If I can mix a diy refractory for a kiln wall then shouldn't I be able to use the same refractory, at the appropriate thickness, for shelves.

Recommendations, short of buying kiln shelves?

Edited by hanee
missing words, lack of clarity

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Just stack them in there, I think that's fine.  I've seen YouTube videos of Japanese kiln openings and stuff is stacked on the floors all the way from front to back.  You won't be getting any natural ash glazing at lowfire so you don't even need to worry at all.  I think they normally stack with wadding between items that are stacked. 

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You can tumble stack the ware, but there's a certain look to the work that comes with that. Even at low fire temps you will probably see some markings due to the stacking arrangement. Pieces are separated with wadding, a mixture of fireclay and sand. You cannot glaze your pieces if you tumble stack, with the exception of some Shino glazes.

Alternatively, you can make your own kiln shelves, but they won't perform anywhere near as well as the ones you can buy.

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Excellent! Thanks to both of you for the reassurances. It sounds like I can ignore kiln shelf advice I'm reading in my particular application. It was seeming to be a blocker before since some of the kiln building books say "start designing your kiln with what sized kiln shelves you will use."

The way I am understanding it at this point is that the kiln shelf usage has to do with the aesthetic requirements of the final product (neatness, consistency) and/or fusing issues at higher temps through either natural (ash) or artificial glazing.

So basically, at least in my application, If I can find a way to stack works without breaking them before firing, and if I can work with any consequence of irregular patination where works touch supports or other works (which can be reduced with wadding), then there are no other mystery issues to account for.

Perhaps a specific positive on the side of no-shelves is less draft blockage.

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Hope you will post some pics of your stacking and the fired results when you do this! Just FYI, the New Hampshire Potters' Guild is open to anyone--we have members in Maine and other New England states. Many do wood firing and there is some real longevity of expertise, incluidng with kiln-building. The Guild has it's own wood kiln, also. Check it out           https://www.nhpottersguild.org/

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37 minutes ago, LeeU said:

Hope you will post some pics of your stacking and the fired results when you do this! Just FYI, the New Hampshire Potters' Guild is open to anyone--we have members in Maine and other New England states. Many do wood firing and there is some real longevity of expertise, incluidng with kiln-building. The Guild has it's own wood kiln, also. Check it out           https://www.nhpottersguild.org/

You have any bumper stickers that say Pot Free or Die??? that would go with all my pottery bumper stickers on my van,

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On 5/24/2019 at 12:14 AM, Mark C. said:

Pot Free or Die

That is just perfect!! U R 2 funny! I will be bringing the suggestion to the next meeting--we need some promotional hooks!! 

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Stacking without shelves only works if you're firing pots that can be stacked vertically without lateral support, like say a stack of planters of the same size. And even then it requires that you leave the foot ring and lip of each pot unglazed so they don't fuse together. However, a raw lip is not desirable in most functional ware, and small pots can't be vertically stacked very well, if at all. In cone 6 and higher firings, there is a much greater chance of pieces warping when stacked that way. Saggars also allow for vertical stacking without shelves.

Tumble stacking only works if you can utilize the side walls of the kiln to support the stack, like in tunnel-type wood kilns. Otherwise you just end up with a pyramid of pots, which is not an efficient use of space and will negatively effect the flame path. In cross draft wood kilns you can't usually utilize the side walls of the kiln. Same goes for gas and electric kilns.

For most potters there are actually very few applications where not using shelves works. Depending on the design of your wood kiln and your aesthetic choices, it may work for you.

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I think it's really laudable to think outside the box and try to figure out a way to fire without shelves but there are times when you just need to spend the money and buy the necessary gear. Cost of shelves versus a firing of subpar work? The only alternative to shelves or stacking pots with wadding between them I can think of is to use saggers but given the description of your work that doesn't sound like an option. 

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Hi Neil,

In my case, I'm not a potter, nor am I using glazes, nor am I firing to higher temperatures, nor am I stacking regular forms -- I can definitely see how stacking a set of regular forms would likely benefit from kiln shelves, but some of your comments really don't have much to do with the particulars of my stated application. So, I think you've tended to re-enforce the idea that  kiln shelves go hand and hand with a need to consistently stack sets of glazed pots efficiently, and thus, they are of more limited utility for low-fire, unglazed terracotta figure sculptures.

You've definitely re-enforced the idea that the type of kiln will largely affect how usable it is without (or with) shelves. For example, Steve Mills' "Philosopher's Kiln" really has no need for shelves nor an easy ability to use them due to the shape of its firing box being squat and long to begin with, whereas a very large kiln with a perfect consolidated cube of space would benefit quite a bit from saggars or shelves. Assuming the kiln is built to the type of work you're doing it should be able to be built without a need for shelves, though, I think, regardless of what your particular aesthetic or functional demands are.

Really, my ideal would be a kiln the size of a couple busts or a couple figures, since none of my work stacks well to begin with (with or without kiln shelves).

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1 hour ago, Min said:

I think it's really laudable to think outside the box [...] but there are times when you just need to spend the money and buy the necessary gear.

This argument is always something I'm extremely suspicious of, and while it may not be that you intend it the way I read it, it's worth exploring a bit, none the less:

Did Michelangelo, Bernini, Canova, Carpeaux, Clodion or Pigalet prefer silicone carbide or cordierite shelves for their wood fired terracottas?

How about stacking and properly firing early Indian lifesize clay figures?  (most of which were fired by merely making a bonfire right up against the work in place -- highly underfired and yet they've survived 1000 years with outstretched arms with individual fingers making graceful and delicate motions).

Where's this box I'm thinking outside of? It seems to me more like a very tiny bubble in history.

Definitely a bubble, as its concave, mirror-like surface makes things inside it appear bigger than they are. It causes a sort of historic myopia.

Most of the "right ways" to do things these days are simply a list of products to buy (like kiln shelves, electric potters wheels, pug mills) all of which didn't exist a very short historical time ago. I understand we all have to make a living and pragmatism is a totally acceptable philosophy -- but these days we tend to have convinced ourselves our pragmatic choice is *superior*, rather than merely *the easiest thing we can do*.

It is a bit sad, though, that compared to most in the past, most of us modern day "makers", don't really make much of our work: in most cases our machines make things for us and then we come in and knit together a few final details. We do all the "important parts" like thinking that we're choosing a shape (among those that our machines make easily formable) or a color (among our 'rich' pallet of lab-engineered, repeatable pigments).

This is all said to be the route to perfection and efficiency, yet, oddly, not many seem to be lamenting the supposedly inherent imperfection or inefficiency of work made 100 or 1000 years ago.

-----

I would love to learn about some pre-industrial kiln shelves, but so far no one has given any historical equivalent. That makes sense, since it's sort of an absurd engineering problem -- similar to a flat-top kiln or a flat roof that has to handle snow-load. It can only be solved with the really-big-hammer approach of high-technology materials. A free-span dead-horizontal is just not what the materials themselves would dictate, it's a carefully engineered imposition. Like steel beams and plywood.

I'm guessing if there were any shelves to speak of they'd have been metal bars, probably cast iron (in the cultures that had the metallurgic technology to support it), and they would wear out relatively quickly.

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Yes, I do believe you read what I wrote the wrong way.

Your title of this thread is “Self-reliant alternative to buying kiln shelves? Historical approaches?” I was giving you a historical approach to firing without kiln shelves. Thank you, yes, I am aware of the terra cotta warriors and other works fired without shelves.

Like Neil said earlier you could make your shelves but in all likelihood they won’t be as durable as commercially made ones.

Pottery Making Illustrated, June 2017 edition has an article by Glynnis Lessing on making kiln setters. She uses a recipe from Barbara Zaveruha. If it’s any use to you the recipe is: talc 20, Tennessee ball clay 25, 100 mesh mullet 55. She uses them to cone 10 oxidation or reduction. The largest of the setters she makes from this mix is 16” on each side of a triangular shape. Don’t know how it would stand up to the weight of a sculpture versus as used for domestic wares. There are a number recipes that can be found online using refractory mixes of fireclay, crushed brick etc. Long slow firing cycle to develop long mullite spinel structures is necessary to add strength to the shelves. Historically I would have to assume trial and error method of using local materials to make furniture would have been used.

Edited by Min

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