|Monthly Tech-Tip |
Modified: 2022-04-06 22:56:16
|New Zealand Kaolin||227.00||KG||48.5|
|Ferro Frit 3110||300.00||LB||29.1|
|Mason 6336 Blue Stain||250.00||GM||0.1|
This body is not available for sale. It is a fritware porcelain (frit is the flux instead of the traditional feldspar). Frits melt far low temperatures so this supercharges the firing maturity.
A long series of test mixes in search of a blend of North American materials found that the glassy phase of the frit amplifies the color of any iron in the kaolin (even tiny amounts). No kaolins available to us were suitable except Grolleg and New Zealand Kaolin (it contains only 0.15% iron). NZK is short, so lots of VeeGum is needed. A pinkish color still remains making it necessary to add a small amount of blue stain (giving it the color of cone 10 reduction porcelain). Propeller mix it very thoroughly and be careful about substituting that stain, agglomerates during mixing produce ugly blue fired specks!
This body pairs with G2931K clear glaze (the fully fritted version of G2931F) and a drop-and-soak firing glaze schedule.
The secrets of this body are thus:
-The 30% frit: Frit is expensive but it makes the impossible possible!
-The NZ Kaolin: The whitest available in the world.
-The VeeGum: Super plastic super-white. Bentone also works.
-The silica for glaze fit and as a structural framework.
As noted, this body will be among the most plastic you have ever used (of any kind). But this is only true if it is stiff enough. Do not use it soft, the shrinkage will be much higher and you risk drying cracks.
Higher than normal firing shrinkage is a part of using this type of body. But that also indicates very high density and strength.
This frit is slightly soluble. That means that on storage it will affect stiffness in the plastic clay or affect the rheology of a casting slip. It can affect plaster and your plaster table.
If we were to manufacture this is could cost $150 a box. But before dismissing this think about the advantages of using it for making smaller pieces:
-Fast firing: As little as 3 hours cold-to-cold.
-The appearance of cone 10R but with far brighter colors.
-Throw ware ultra thin and light.
-A perfectly fitted ultra-clear dipping glaze that is far cheaper to make than commercial glazes.
-Dramatic reduction in wear-and-tear on kiln elements and energy usage.
A final note: Because this body matures at such a low temperature it needs to be bisqued much lower (around 1500F. if ware is not absorbent enough fire lower).
Units-of-measure: I have specified 50 lb bags to fill the needed amount for the NZ kaolin, however it comes in 20kg bags. But you are likely mixing in grams or ounces so just refer to the percentage column.
This is an all-fritted version of G2931F Zero3 transparent glaze. I formulated this glaze by calculating what mix of frits must be employed to supply the same chemistry of the G2931F recipe. The mug is made from the Zero3 porcelain body (fired at cone 03) with this glaze. This glaze fits both the porcelain and the Zero3 terra cotta stoneware. The clarity, gloss, fit and durability of this glaze are outstanding.
Look at how translucent this is! I can fire one of these in three hours, cold-to-cold. I am casting them with molds made using the 3D-printing process. Anyone could do this. Incredibly exciting. And with the G3879 glaze it looks awesome, just like bone china. Notwithstanding this, the Zero3 recipe has to be altered for casting. Initially I have reduced the VeeGum to 1% but it is still casting too slow. And it is not shrinking enough to pull away from the mold well. I am considering strategies on how to increase drying shrinkage and am going to add more frit to take it down to cone 04.
I propeller-mixed a 5 gallon pail of the slurry yesterday. Overnight it forms a gel in the pail. That means that whenever I need some I can simply scoop it out and lay it on the batt in a thick layer. This is about 6 kg, it will take about two days to dewater enough (undisturbed) for use.
These fritted porcelain bars are fired at cone 06, 04, 03 and 02 oxidation (bottom to top). The body contains 0.2% blue stain. Notice that almost no color develops at the lowest temperature. Glass development is needed.
This porcelain mug put into kiln at 8:45am and I was drinking coffee from it at 12:15! How? One way to fast-fire is to fire a lot lower. This is Zero3 porcelain made using Dragonite Halloysite (not quite as white-burning as New Zealand Halloysite). It is the L2934C recipe. It was fired to cone 03 and glazed with G2931K clear glaze (which has fired crystal clear and flawless). I fired at 1200F/hr to 1950F, held it for 15 minutes, cooled at 999F/hr to 1850F and held it for 30 minutes, then dropped as fast as the kiln would do. Is this really porcelain? Yes. And it is super strong. The frit in the recipe is magic, making it vitrify quickly and completely.
Want to make this incredible porcelain and glaze yourself? Read on. The mug on the left is a cone 10R (2350F/1290C) porcelain (#6 Tile kaolin and Nepheline Syenite) with G1947U clear glaze. The other is a fritted cone 03 (1950F or 1065C) porcelain (NZ Kaolin, Ferro Frit 3110) with G2931K clear glaze. We call the body/glaze/firing system "Zero3" (google it or use the links here). The Zero3 porcelain is blue-white instead of grey, the glaze is crystal clear, underglaze colors are so much more vibrant. This Zero3 mug was fired in 3 hours (cold-to-cold). It fits glazes really well, it is very strong and much more translucent. How is this possible? The magic of the frit, it melts so much better than nepheline. It is the most expensive body you will ever make. But from it you may create the highest quality ware you have ever made using the most plastic body you have ever thrown! Follow the instructions carefully.
The designation for a group recipes for body, glaze and engobe (by Tony Hansen), that potters can use to make low fire stoneware and fritware porcelain at 1100C (2000F) or cone 03.
Zero3 porcelain/stoneware, engobe, clear glaze and firing schedule
Plainsman Zero3 Glaze L,K,H and Firing Schedule
G2931K - Low Fire Fritted Zero3 Transparent Glaze
A cone 03-02 clear medium-expansio glaze developed from Worthington Clear.
G2931H - Ulexite High Expansion Zero3 Clear Glaze
A cone 03-02 higher expansion fritted clear glaze developed from Worthington Clear.
L3724F - Cone 03 Terra Cotta Stoneware
An experimental Zero3 using Plainsman 3D clay
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|By Tony Hansen|
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