Refractory premium mixes for making kiln furniture, kiln wash, casting mixes

Plastic Refractory Alumina Body H1

Shelf Clay

Total:100.30

Notes

This has excellent plasticity. Use it for rolling refractory slabs (to make super-thin kiln shelves for our small test kilns) or forming other shapes. Dry pieces evenly to prevent warping during drying.

This will fire to much higher temperatures than anything your kilns is likely to produce, just fire shelves as high as you can.

This is the product of a series of tests that had high alumina percentages. But did not have good thermal shock resistance (this adds Kyanite aggregate to improve that) and whose working properties were not robust enough (thus the 30% added ball clay in this recipe). The bentonite augments the plasticity. The barium precipitates soluble salts during drying.

This recipe compromises the service temperature (compared to previous ones having higher percentages of alumina) but this body should still be plenty refractory enough for any common pottery or ceramics purpose.

Pictures

L3693H1 kiln shelf

Plainsman Super Kiln Wash

Total:814.00

Notes

This produces a super-refractory powder layer that stays in place and does not harden after many firings like common 50:50 kaolin:silica kiln wash. This also does not not shrink and crack nearly as much.

Zircopax is among the most refractory materials in ceramics, so it was chosen to form the bulk of the dry mix (calcined alumina could also be used).

Strangely, calcined, rather than raw kaolin, imparts multiple advantages:
-Better coverage.
-It does not shrink and crack.
-Much less water is needed.
-Normally the raw kaolin suspends the slurry, makes it brushable (just barely) and hardens it on drying. But CMC gum hardens even better and makes it work like paint (suitable even for use with a paint roller).
-Dries far slower. Even on absorbent alumina shelves an even and thin layer can be applied effectively.

This recipe produces enough to fill a pint jar. The Laguna gum solution has 6.7g CMC Gum per 100g - if you do not have it then add 7.5g powdered CMC and 313 total water. It is a little difficult to get all the powder into this amount of water, however a thin paintable slurry is produced. While blender mixing would seem best, your mixer may not have enough power (because this type of slurry is subject to a phenomenon known as "shear thickening". A propeller mixer should be fine for the gum solution version, but for powdered gum, mixing, aging for a few days and mixing again might be needed.

Specific gravity: 1.87
Approximate retail cost: $7.50
One pint coverage (single-coat): Nine 12 x 24 gas kiln shelves (about 18 square feet).

The use of calcined kaolin brings issues with the slurry settling in a hard layer (flocculating with Epsom salts and calcium chloride was tried, but that is not realistic with a slurry having such a high specific gravity). The hard material can be stirred back with effort and it remains usable for a few days (in all, we feel the benefits outweigh these issues). It is possible settling could be prevented by using a raw:calcine mix of kaolin (but other properties would be compromised). If you find a way to keep it from settling please let us know.

The Dettol was needed to alleviate the rotten smell (bacteria seems to like this recipe!).

Pictures

L4001 Kiln wash (left) vs. typical kaolin:silica wash (right)

The new wash has been fired on and is adhering well, not shrinking or cracking and is not powdery. The layer is much thinner. The other side has been fired many times and the flakes stick to the foot rings of every piece fired in the kiln.

Super Kiln Wash

Plastic Refractory (heavy duty)

Total:119.00

Notes

The original intent of this test was to make a super duty tapper clay (for the foundry industry). But, this is also be suitable as a general-purpose plastic refractory akin to a fireclay. This recipe employs alumina instead of the silica used in L4404A (the higher heat duty this will give obviously comes at higher expense).

Ball clays and kaolins are actually very refractory materials, more so than fireclays. And they are inexpensive and easily available. By incorporating alumina the service temperature is being extended considerably (compared to what it would be with just the kaolin and ball clay). And the grog reduces firing shrinkage.

Tile #6 kaolin is highly plastic and it, combined with the ball clay, give this excellent plasticity for forming.

Firing shrinkage varies only 1.5% from cone 5 to 10R. Likewise, porosity only varies about 2% across this range. This will fire considerably higher that cone 10 with no problems.

Pictures

White synthetic fireclay L4404B fired bars

Cone 5 (bottom) to 10R (top).

Refractory Casting Slip

Total:142.22

Notes

This is used to make melt flow testers. It is very refractory, still highly porous even at cone 10. We are able to cast pieces of very thin walls and they do not warp in firing even at cone 6.

This has excellent casting properties and releases from molds quickly. It ages well without change to the rheology.

We make 5000g batches and get about 1.78 SG from this mix. Aging may require the addition of a little more Darvan or water.

Pictures

L4404A without and with L3693E liner

These frit ingots have melted to cone 04 and slow cooled. We used cast crucibles made from L4404A refractory slip. The front one has an alumina oxide liner of L3693E. Without the liner, the ingot in the back is inseparable from the body. But with the liner (front), it easily breaks away. The alumina has remained as a powder and can be easily cleaned off the ingot leaving almost no residue. Frit manufacturers crash cool frit batches by quenching them in water, this one was slow-cooled, we are hoping that will make the difference to enable it to pass a lead leaching test.

Alumina Wadding #2

Total:100.00

Notes

The objective of this recipe is a plastic material that is also refractory (for making wadding when loading kilns). This recipe was found to be better than one using hydrated alumina (lower firing shrinkage).

Although not very plastic, this does not split during wedging so it is suitable for forming and pressing into molds. For better plasticity a more plastic kaolin could be used (e.g. #6 tile is far more eplastic).

It would also be possible to slip cast this (although 0.5-1.0% Veegum might be needed to give it enough plastic strength to pull away from the mold).

The total shrinkage is 8-9% across the range from cone 8-10. At cone 6 will be less, likely around 7%.

Pictures

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