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See Also:
Zero3 Red Stoneware body, white engobe, glaze, firing schedule
Replacing Talc with Nepheline Syenite in Cone 04 White Body
Terra Cotta is often associated with indigenous cultures or school art programs. But actually, a quality terra cotta with a good glaze can produce ware of excellent durability.
Project Name Casting strong and durable terra cotta at cone 04 Project Codenumber UnAssigned Notes Terra Cotta is being discovered by many potters (and hobbyists with interest in production) as being stronger and more durable than they thought. And firing at cone 04 is so much easier and faster than for stoneware. And the colors available are much brighter than at high temperatures. It seems there are thousands of commercial glaze products for use at cone 06-04. And it is just as easy to mix your own glazes. |
L215 Terra Cotta Casting #1
Total:144.96 Notes *Note: This recipe is superseded by L4170B, a 90:10 blend of Redart/Ball Clay to get faster casting. However the notes below are still applicable. Pictures G3879 Clear on L4170 TerraCotta Casting ![]() The clear glaze is G3879. The white on the outside of the one on the left has 10% added zircopax. The overglaze colors are Spectrum Majolica colors. L4170 TerraCotta with G3879 zircon white ![]() The insides of both are done with a 10% zircopax-added version of G3879. I compared it with Spectrum Majolica white (on the outside of the one on the right, it had to be painted on), the potential to get a much more even coverage is there because we can dip-glaze this one. The outside color tests on the left are Crysanthos Underglazes. L4170 at cone 06, 02, 1 (bottom to top) ![]() Cone 1 is stoneware strength. Cone 02 is the warmest color. But cone 04 (not shown) is also pretty good. G3879 at cone 1 on a terra cotta body ![]() This combination qualifies as a stoneware, the body has less that 2% porosity at this temperature. Fired Redart, Tuckers, M2 bars cone 02, 04 ![]() Top to bottom: L4170 Redart casting body L4183 Tuckers terra cotta L4184 M2 throwing body Testdata SHAB - Shrinkage/Absorption
XML (to paste into Insight) <?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="L215 Terra Cotta Casting #1" id="155277" key="MGw3SdYM" date="2021-02-17" codenum="L4170"> <recipelines> <recipeline material="Redart" amount="80.000" tolerance=""/> <recipeline material="KT1-4 Ball Clay" amount="20.000" tolerance=""/> <recipeline material="Water" amount="44.000" added="true"/> <recipeline material="Darvan #811" amount="0.960" added="true"/> </recipelines> </recipe> </recipes> Born: 2019-03-20, Modified: 2021-02-17 10:17:37 |
L215 Terra Cotta Casting #3
Total:144.96 Notes *This reduces the amount of ball clay in L4170 to speed up casting time (at risk of mold release and tearing). This has proven to work well. The casting behaviour is still good and release is quicker. Comments 2021-03-02 Joe: Jan. 4/21 2021-03-02 Joe: Repeat of above mix Feb.8/21 2021-03-02 Joe: Feb. 22/21 doubled recipe to 10 KG. powder quantity, mixed briefly and let sit overnight. Next morning no water sitting on surface of slip in 20 litre pail, so, even more surface area than approx. 7 litre Canadian Tire Bucket. This amount mixed quite well with lab mixer, but any more and the large mixer would be required, and was used for initial mixing first day. Pictures G1916Q on L4170 cast pieces ![]() G1916Q on L4170 ![]() Thin application is clearly the way to get the best transparent. Cone 04 L3685Z2 white engobe with clear glazes ![]() The colour as amazingly white. And this engobe appears to be fitting very well even though we are dipping pieces, like a glaze, to bisque ware. Handles are L215 P6877 pugged clay ![]() Handles are L215 P6877 pugged clay attached to mugs with the L4170B slip which acts like glue, a minimal amount required to attach handles. No cracking evident anywhere around handles. L4170B at cone 04, 2 ![]() Very dense and strong at cone 2, it’s fired surface is almost velvety, very pleasant to touch. Untitled ![]() Untitled ![]() Untitled ![]() Untitled ![]() L4170B bars fired cone 04-5 (bottom to top) ![]() Testdata SHAB - Shrinkage/Absorption
XML (to paste into Insight) <?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="L215 Terra Cotta Casting #3" id="189412" key="PteytFQ5" date="2021-03-08" codenum="L4170B"> <recipelines> <recipeline material="Redart" amount="90.000" tolerance=""/> <recipeline material="KT #1-4 Ball Clay" amount="10.000" tolerance=""/> <recipeline material="Water" amount="44.000" added="true"/> <recipeline material="Darvan #7" amount="0.960" added="true"/> </recipelines> </recipe> </recipes> Born: 2019-03-20, Modified: 2021-03-08 14:29:25 |
White Engobe #2
Total:124.50 Notes *This is the product of a long development program that culminated in the realization that a super-white engobe requires using super-white kaolins and bentonites and plenty of zircopax. And that it is possible to dip and paint engobes on bisque if the slurry is conditioned with gum. This recipe looks so good because it promises to enable the strength of terra cotta with the whiteness of porcelain. This in turn promises to provide white surfaces for brush work and transparent overglazes that produce brilliant gloss and colors not achievable at high temperatures. Pictures L3685Z1 and L3685Z2 at cone 04 ![]() Z2, this improved version, is much whiter. On Plainsman L210. Fit is amazing for Z2. And it is incredibly white. L4170B with L3685Z2 engobe ![]() With the gum additions, it applied very evenly to the bisque (using a pour-in pour-our technique). The layer was very thin yet covers very well. Cone 04 L3685Z2 white engobe with clear glazes ![]() The colour as amazingly white. And this engobe appears to be fitting very well even though we are dipping pieces, like a glaze, to bisque ware. L215 with L3685Z2 engobe at cone 04 ![]() Although a very thin layer it completely covers the dark red body. On L215 cone 03+ shivers on rim ![]() Cone 1-6 (bottom to top), cone 01, 02 at top ![]() Testdata SHAB - Shrinkage/Absorption
XML (to paste into Insight) <?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="White Engobe #2" id="191314" key="7KDgsotk" date="2021-03-08" codenum="L3685Z2"> <recipelines> <recipeline material="Nepheline Syenite" amount="20.000" tolerance=""/> <recipeline material="New Zealand Kaolin" amount="55.000" tolerance=""/> <recipeline material="Silica" amount="25.000" tolerance=""/> <recipeline material="Veegum" amount="3.000" added="true"/> <recipeline material="CMC Gum" amount="1.000" added="true"/> <recipeline material="Zircopax" amount="20.000" added="true"/> <recipeline material="Epsom Salts" amount="0.500" added="true"/> </recipelines> </recipe> </recipes> Born: 2014-11-04, Modified: 2021-03-08 14:33:50 |
Cone 03-04 Expansion Adjustable Gloss Base
Total:102.00
Notes *This recipe provides the greatest thermal expansion adjustability we have seen in a low fire clear glaze. It combines a middle-of-the-road thermal expansion frit with a very low and very high expansion frit (they cancel each other out but increase gloss of the otherwise silky Frit 3195). Pictures G1916Q at Cone 01 on 3D+iron ![]() Very nice results on L3724E red body at cone 01. Piece is very strong. 1916J and Q fired to 1450F ![]() These glazes are starting to melt, the surface having reached the consistency of a porcelain and have densitfied to very low porosity. Notice the iron in the ball clay really shows up at this stage (it will be less evident later). G1916Q Cone 04 using 04DSSC schedule ![]() Counterclockwise: L212, Raku, Buffstone, L213, L210, L215 Crazing out-of-the-kiln on Raku and buffstone. Bisque 04-03. G1916Q and J fired 1650-2000F ![]() Ten-gram balls melted and flattened as they fired. They soften over a wide range, starting well below cone 010! At 1650F carbon material is still visible (even though the glaze has lost 2% of its weight to this point), it is likely the source of the micro-bubbles that completely opacify the matrix even at 1950F (cone 04). This is an 85% fritted glaze, yet it still has carbon; think of what a raw glaze might have! Of course, this is a thick layer, so the bubbles are expected. But they still can be an issue on a piece of ware. So to get the most transparent possible result it is wise to fire tests to find the point where the glaze starts to soften (1450F in this case), then soak the kiln just below that (on the way up) to fire away as much of the carbon as possible. Success with cyrstal clear glaze cone 03 ![]() Uses Cone 03 soak-soak-slow cool schedule. Left: P6282 with 3685U slip and 1916Q. Clear and very good. Glaze is thicker than the other two. Shivering on lip, the slip is not fitting the body. Center: P6282 with G2931F Ulexite clear. Better clarity even though it is applied very thin. Shivering on lip, the slip is not fitting the body. Right: L3724F with 3685U slip. No shivering. Very good coverage of the glaze, very clear, the best I have seen yet! G1916Q on L215, L212, L210, L213, Buffstone at cone 03 ![]() All exited from the klin without crazing. The L215, L213, L210 and L212 samples subsequently survived a 300F/Icewater test without crazing, but the Buffstone did not. The L213 would not likely survive a cold-to-hot test without shivering. 1916Q cone 04, 03 ![]() Both were slow cooled. While the cone 04 version is glassy and ultra-gloss, it has significant clouding of micro-bubbles. The cone 03 version, right, is completely transparent. G1916Q on L210 fired at cone 04 ![]() G1916Q+2%Iron on L212 talc body fired at cone 05 ![]() This will likely shiver over time. But the speckle that happens on white bodies is clearly visible. XML (to paste into Insight) <?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Cone 03-04 Expansion Adjustable Gloss Base" id="56565" key="nReLCQao" date="2021-02-17" codenum="G1916Q"> <recipelines> <recipeline material="Ferro Frit 3195" amount="65.000" tolerance=""/> <recipeline material="Ferro Frit 3110" amount="10.000" tolerance=""/> <recipeline material="Ferro Frit 3249" amount="10.000" tolerance=""/> <recipeline material="No. 5 Ball Clay" amount="15.000" tolerance=""/> <recipeline material="Red Iron Oxide" amount="2.000" added="true"/> </recipelines> </recipe> </recipes> Born: 2014-03-04, Modified: 2021-02-17 11:03:09 |