Making your own kiln posts, is that even practical?

Supply chain issues during Covid made it difficult to get posts. I wondered if I could make my own. I have access to the same ceramic materials that post manufacturers use. Firing to the highest temperature they will ever experience should make them dimensionally stable, for me that is cone 10. In the past it was always a hassle to make the extruder die, but not anymore. An ordinary 3D printed PLA template will easily withstand the pressure in a hand extruder (even if printed with infill). The precision tapering possible is amazing. Notice that the floating centre has a tapered bridge to help clay knit together as it flows around it. What about a refractory plastic body? I started with L4543, it is cheap to make and dries quickly with minimal shrinkage. To cut posts to length with a square end I print sleeves to slide them into. I you would like the 3D drawing it is in the Files manager in Insight-live.com, it is parametric and easy to change.

Related Pictures

Global supply chain issues? Learn to mix and adjust your own bodies, glazes

Material prices are sky rocketing. And, the more complex your supplier's supply chain the more likely they won't be able to deliver. How can you adapt to coming disruption, even turn it into a benefit? Learn to create base recipes for your glazes and even clay bodies. Learn now how to substitute frits and other materials in glazes (get the chemistry of frits you use now so you are ready). Even better: Learn to see your glaze as an oxide formula. Then calculate formula-to-batch to use whatever materials you can get. Learn how to adjust glazes for thermal expansion, temperature, surface, color, etc. And your clay bodies? Develop an organized physical testing regimen now to accumulate data on their properties, learn to understand how each material in the recipe contributes to those properties. Armed with that data you will be able to adjust recipes to adapt to changing supplies.

Thin walled kiln posts using a hand extruder

Shown is a tube hand extruder die (with a floating core). It was 3D printed using ordinary PLA. These posts weigh 23g/in (vs 81g/in for the commercial one shown). The posts were cut square-ended using the length patterns shown. Commercial regular posts will support the weight of a city bus but we are supporting pottery - so a thinner more energy-efficient version seems appropriate. This new drawing has been uploaded (visible in the Files panel in your Insight-live.com account). This drawing is more parametric than version 1, it enables setting the post width, wall thickness, draft of the float and position and angle of the float supports. This clay is normal pottery stiffness and contains ~20% grog and sand. We are experimenting with various refractory mixes (e.g. L4543).

Covid taught us about supply interruptions

Material prices were sky rocketing (and still are). Prepared glaze manufacturers have complex international supply chains. Now might be the time to start learning how to weigh out the ingredients to make your own. Armed with good base glazes that fit your clay body (without crazing or shivering) you will be more resilient to supply issues. Add stains, opacifiers and variegators to the bases to make anything you want. That being said, ingredients in those recipes may become unavailable! That underscores a need to go to the next step and "understand" glaze ingredients. And even improve and adjust recipes. It is not rocket science, it is just work accompanied by organized record-keeping and good labeling.

Make your own vibrating sieve

Being more independent is now cool again. Actually, it is being forced upon us by necessity because of supply chain issues and skyrocketing prices of convenience glazes, bodies, engobes, etc. Independence involves using sieves. True, it is no problem for a potter or lab tech to manually coax a glaze slurry through a small 80# sieve. But real independence is about sieving in volume - clay bodies and casting slips. About making your own porcelains and sieving out agglomerates. The ultimate in independence: Sieving particulates from your own native clay slurries. And doing it at 100, 140 and even 200 mesh. That requires a vibrating sieve. This one cost us less than $100 to make. Of course, a Tyler sieve (or similar) is needed, these can be purchased on Ebay or Amazon. And a vibration motor, some metal and hardware and a friend with metal fabrication tools.

Make your own pyrometric cones? Why not!

Self-supporting cones are a must in each firing but they are expensive. Fortunately the shape of a self-supporting cone is easy to draw in 3D (I did it here in Fusion 360). It is a 25mm equilateral triangle base lofted to a 3mm one 65mm straight up on the front side. And then a cut-out across the front. By using 3D printed molds and plastic clay I can press these by the dozen. What about a recipe? Cones melt short of being glazes but beyond being porcelains. I chose L3685Z3 engobe as a starting point, it has a linear vitrification curve spanning a wide range. Approaching this on the material level, not as a chemistry project, I did three iterations of adding Ferro frit 3110 to the engobe. Shown here are the second, "A" and third, "B" (on the right is an Orton cone 6). B has too much frit, A does not have enough. You likely guessed what I did next: Mixed A and B. The result was almost perfect, bent just a little too much. If you would like this 3D file in Fusion 360 format, it is available in the Files manager in your Insight-live.com account.

My first zircopax kiln shelf

It is 5 mm thick (compared to the 17mm of the cordierite one). It weighs 650 grams (vs. 1700 grams). It will perform at any temperature that my test kiln can do, and far in excess of that. It is made from a body I slurry up (80% Zircopax Plus, 16.5% 60-80 Molochite grog, 3.5% Veegum T). The body is plastic and easy to roll and had 4.2% drying shrinkage at 15.3% water. The shelf warped slightly during drying (I should have dried it between sheets of plasterboard). Firing at cone 4 yielded a shrinkage of 1%. Notice that cone on the shelf: It has not stuck even though no kiln wash was used! Zircopax is super refractory! This is sinter bonded, so the higher the temperature you can fire the stronger it will be. Although it would be very hard to make full 18 or 22-inch shelves for larger kilns, smaller ones designed to "network" would enable a tighter load of ware with a much lower shelf-to-ware weight ratio (especially using my own lightweight posts). Like alumina, this does not have the thermal shock resistance of cordierite, uneven heating can crack these.

Links

URLs	https://insight-live.com/insight/recipes.php?OpenFile=mEjR9hsWFK Kiln post hand extruder die drawing
Projects	Making our own kilns posts using a hand extruder

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