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

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See Also:
Make kiln posts using kaolin, kiln mortar using kyanite

Super-duty refractories can be made using expensive materials and economy versions from common materials. Use the former where needed but the latter most often.

Plastic Refractory Alumina Body H1

Shelf Clay

Code #


Materials Amt
Calcined Alumina 48.000 47.86%
Bentonite 4.000 3.99%
*Kyanite 48 mesh 18.000 17.95%
M23 Ball Clay 30.000 29.91%
Barium Carbonate 0.300 0.30%



*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.


L3693H1 kiln shelf

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Plastic Refractory Alumina Body H1" keywords="Shelf Clay" id="116162" key="9z9KRqih" date="2022-09-19" codenum="L3693H1"> <recipelines> <recipeline material="Calcined Alumina" amount="48.000" tolerance=""/> <recipeline material="Bentonite" amount="4.000" tolerance=""/> <recipeline material="Kyanite 48 mesh" amount="18.000" tolerance=""/> <recipeline material="M23 Ball Clay" amount="30.000" tolerance=""/> <recipeline material="Barium Carbonate" amount="0.300" tolerance=""/> </recipelines> </recipe> </recipes>

Born: 2017-05-05, Modified: 2022-09-19 23:16:49

Plainsman Super Kiln Wash

Code #


Materials Amt Units
Zircopax 400.000 GM 80.00%
Calcined Kaolin 100.000 GM 20.00%
Additions Units
*Laguna Gum Solution 113.000 GM 22.60%
Water 200.000 GM 40.00%
Calcium Chloride 2.000 GM 0.40%

Total:815.00 (R)


*This produces a super-refractory powder layer that stays in place and does not harden excessively after many firings, does not chip or cake, that does not shrink and crack. Because it contains gum it paints on very well, staying wet long enough to level and even out with a brush. Also useful as a refractory ceramic coating.

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). Calcined, rather than raw kaolin, was employed to help densify and stabilize the coverage (by its flat particle shape).

Laguna gum solution was added to harden the dry layer and slow down the drying (drying too fast is a major problem with most kiln washes). The slurry produced paints evenly onto even absorbent alumina shelves, especially with a small paint roller.

This produces enough to fill a pint jar. The Laguna gum solution has 6.6g CMC Gum per 100g. It is a little difficult to mix in the final amount of powder yet a thin paintable slurry is produced (a good propeller mixer is 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).

We continue to have issues with the slurry settling in a hard layer (epsom salts was used in initial testing but it did not prevent settling and the slurry developed a rotten smell). Calcium chloride addition of approx. 2 grams worked for a few days, but returned to hard-panning. However once the hard material is stirred back in it works normally, and the benefits outweigh this issue.
We also added 1 gram of Dettol to this mixture to alleviate rotten smell, and this has worked well over time (if you do not mind the Dettol smell).


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

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Plainsman Super Kiln Wash" id="115132" key="Nrunwed9" date="2021-12-19" codenum="L4001"> <recipelines> <recipeline material="Zircopax" amount="400.000" tolerance="" unitabbr="GM"/> <recipeline material="Calcined Kaolin" amount="100.000" tolerance="" unitabbr="GM"/> <recipeline material="Laguna Gum Solution" amount="113.000" unitabbr="GM" added="true"/> <recipeline material="Water" amount="200.000" unitabbr="GM" added="true"/> <recipeline material="Calcium Chloride" amount="2.000" unitabbr="GM" added="true"/> </recipelines> </recipe> </recipes>

Born: 2017-08-03, Modified: 2021-12-19 22:21:32

Plastic Refractory (heavy duty)

Code #


Materials Amt
Tile #6 Kaolin 33.000 27.73%
*KT1-4 Ball Clay 33.000 27.73%
Calcined Alumina 33.000 27.73%
*STKO 22S Grog 20.000 16.81%



*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.


White synthetic fireclay L4404B fired bars

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


SHAB - Shrinkage/Absorption


XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Plastic Refractory (heavy duty)" id="201083" key="3oRvrQAT" date="2023-07-24" codenum="L4404B"> <recipelines> <recipeline material="Tile #6 Kaolin" amount="33.000" tolerance=""/> <recipeline material="KT1-4 Ball Clay" amount="33.000" tolerance=""/> <recipeline material="Calcined Alumina" amount="33.000" tolerance=""/> <recipeline material="STKO 22S Grog" amount="20.000" tolerance=""/> </recipelines> </recipe> </recipes>

Born: 2021-02-12, Modified: 2023-07-24 22:38:15

Refractory Casting Slip

Code #


Materials Amt
Pioneer Kaolin 35.000 24.61%
*KT1-4 Ball Clay 35.000 24.61%
Silica 30.000 21.09%
Water 41.580 29.24%
*Darvan #7 0.640 0.45%



*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.


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.

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Refractory Casting Slip" id="194791" key="eW9nW7FR" date="2024-03-03" codenum="L4404A"> <recipelines> <recipeline material="Pioneer Kaolin" amount="35.000" tolerance=""/> <recipeline material="KT1-4 Ball Clay" amount="35.000" tolerance=""/> <recipeline material="Silica" amount="30.000" tolerance=""/> <recipeline material="Water" amount="41.580" tolerance=""/> <recipeline material="Darvan #7" amount="0.640" tolerance=""/> </recipelines> </recipe> </recipes>

Born: 2021-02-12, Modified: 2024-03-03 01:10:36

Alumina Wadding #2

Code #


Materials Amt
Calcined Alumina 50.000
EPK 50.000



*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%.




SHAB - Shrinkage/Absorption


LDW - LOI/Density/Water Content


XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Alumina Wadding #2" id="210350" key="pjWmDn19" date="2023-01-06" codenum="L4482B"> <recipelines> <recipeline material="Calcined Alumina" amount="50.000" tolerance=""/> <recipeline material="EPK" amount="50.000" tolerance=""/> </recipelines> </recipe> </recipes>

Born: 2021-12-22, Modified: 2023-01-06 19:20:13