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See Also:
Zero3 Ulexite-based glaze, engobe and firing schedule
Replace talc with a nepheline syenite:dolomite mix in low fire white clay bodies
If you are doing low temperature earthen ware, especially for functional pottery, then start with a good transparent base clear recipe. Read about all of these and choose.
Project Name Low Fire Clear Glaze Comparison Project Codenumber UnAssigned Notes A good base clear for low temperature ceramics is vital for success. It can become the base of all of your coloured glazes. And a kiln firing situation where you can do lots of testing is important. After all, if you can do a firing in 3 hours, it is much more practical to do testing. URLs |
Deb's Clear Cone 04-02
Total:100.00 Auto Unity Formula
Notes *A well known clear for low temperature, especially terra cotta. Sources often caution against applying too thickly to avoid clouding. We found the same issue. Many use this this as an alternative to Worthington Clear. Its thermal expansion is considerably higher. Pictures XML (to paste into Insight) <?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Deb&#039;s Clear Cone 04-02" id="70214" key="cBTAinru" date="2017-03-10" codenum="G2932" picturebasename=""> <recipelines> <recipeline material="Ferro Frit 3134" amount="30.000" tolerance=""/> <recipeline material="Ferro Frit 3195" amount="45.000" tolerance=""/> <recipeline material="EP Kaolin" amount="25.000" tolerance=""/> </recipelines> </recipe> </recipes> Born: 2014-03-17, Modified: 2017-03-10 23:15:34 |
Worthington Cone 06-2 Clear Gelling, High LOI, Gerstley Borate difficult to sub, High Boron
Total:100.00 Auto Unity Formula
Notes *This recipe is a common Gerstley Borate clear base used from 04 all the way to cone 6! At higher temperatures the recipe trends toward less kaolin to more silica and a little less GB (e.g. 50:20:30). Pictures Worthinton Clear at cone 01 ![]() On a terra cotta clay at this temperature was has stoneware properties. The fired surface is good. Worthington Clear vs. Fritted Clear ![]() Worthington (right) flows even better than the fritted glaze and does not have any more entrained bubbles even though it has an LOI of 20%. This is likely because its melting history and behavior is such that its ability handle gases of decomposition from the body and its own materials is so much better. 2931 vs 2931b ![]() On Plainsman L215 cone 02 the original base Worthington Clear has gone on very thin on sides of mug (because of the low specific gravity necessary to prevent it from gelling it is very difficult to get it on thick enough). The fired surface is clear but not as glossy. On the rim it has bubbles. The Ulexite version (G2931B) is glossier, and went on thicker because the slurry is so much easier to use. This glaze is not recommend for L215, the latter contains talc that increases its thermal expansion, putting too much squeeze on this glaze. Entrained bubbles in Worthington Clear ![]() This is a 16X closeup of flow test (10 gram ball melted down onto a tile) that concentrates bubbles. There are high populations of large and tiny ones. The larger ones are from the Gerstley Borate, the tiny ones from the kaolin. GB vs Ulexite Clear glaze bubbles ![]() These are 10 gram balls fired down onto tiles at cone 04 to compare melt fluidity and bubble populations in three clear glazes. Larger bubbles are better, they break at the glaze surface and heal. Tiny ones produce cloudiness. Worthington Clear the next day ![]() Even though this has a low specific gravity and is deflocculated with darvan, the next day it is still jelly. Impossible to use unless more Darvan is added, who knows where that will go! G2922G, G2931 flow tests ![]() Testdata 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="Worthington Cone 06-2 Clear" keywords="Gelling, High LOI, Gerstley Borate difficult to sub, High Boron" id="56711" key="7u4JoeCP" date="2023-04-13" codenum="G2931" picturebasename=""> <recipelines> <recipeline material="Gerstley Borate" amount="55.000" tolerance=""/> <recipeline material="EPK" amount="30.000" tolerance=""/> <recipeline material="Silica" amount="15.000" tolerance=""/> </recipelines> </recipe> </recipes> Born: 2014-03-17, Modified: 2023-04-13 22:30:05 |
Zero3 K Cone 03 Transparent Glaze
Total:95.00 Auto Unity Formula
Notes *This recipe improved on the popular Worthington Gerstley-Borate-based low fire clear recipe. It targeted cone 03 to work best on Zero3 stoneware and porcelain. To fire lower (cone 06-04), consider G1916Q (or derivatives) instead. Batch Ticket Notes These notes were entered in the notes panel under "Batch Ticket Notes" Pictures G2931K on Zero3 Stoneware ![]() Fired cone 03. Body is Zero3 stoneware. G2931F vs. G2931K on Polar Ice Low Fire ![]() 2931F was the Ulexite flused version of this recipe. The F survived three boil:ice cycles and 1 300F:ice cycle without crazing or shivering. G2931F vs G2931K fritted - terra cotta mugs cone 03 ![]() F was the Ulexite-fluxed version of this recipe. G2931F vs G2931K flow test ![]() These two recipes have the same chemistry, but K sources boron from frits rather than Ulexite. Notice how much less bubbles there are in the flow and how much more predictable the melting pattern is. G2931F vs G2931K - Melted balls at cone 03 ![]() F, the Ulexite version, is obviously bubbling more, the percolation is causing the melt to spread out more on the tile. On the flow test is was less fluid. Firing temperature is important for Zero3 glaze ![]() This is G2931F on Plainsman Buffstone, L213, F100, L215. First column is cone 04, center is cone 03, right is cone 02. All exited the kiln without crazing except Buffstone at cone 04. Three low fire bodies that need three clear glazes ![]() Because of glaze fit. Left: Plainsman Buffstone, contains no talc, fires buff. Center: L212 (about 25% talc). Right: L213 (about 45% talc, fires whiter). Talc raises thermal expansion. The centre glaze is G2931K (Insight-live reports COE 7.4), it fits L215 (also Zero3 porcelain and stoneware). It crazes on Buffstone and shivers on L213 and L212. G2931L has lower expansion (to work on zero-talc porous bodies). G2931H is higher (for talc bodies like L213). G2931K glaze precipitates things on storage ![]() G2931K On L212 after a year ![]() Some crazing starting. K on L215 at cone 04 ![]() The thicker version is clouding. The thinner one has micro-pinholes. It needs a higher temperature. G2931K o L215 - Cone 03, thick application ![]() G2931K on L215 - Cone 03 fired in 30 minutes ![]() Very transparent. No crazingafter many months. G2931K on L215 - Cone 06 ![]() Milky (because cone 06 is underfired for this glaze). But only a little crazing after a year. G2931K running on Zero3 Casting ![]() This happened at cone 03 and 04. The G3879 (left) did not run. For some reason G2931K easy applies to thickly on this body. This 1000 gram batch of glaze powde ![]() This 1000 gram batch of glaze powder screened 80 mesh immediately after making, and allowed to sit for 3 months prior to usage. G1916Q (left) vs G2931K (right) at cone 04 ![]() On a terra cotta body, the G1916Q is performing better, there are less micro bubbles. URLs How to tune the thixotropy of a glaze How to convert a d..o a brushing glaze Typecodes ST-Untitled typecode Alternate Code Number:GS04-1 XML (to paste into Insight) <?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Zero3 K Cone 03 Transparent Glaze" id="95671" key="dQ9ZQbNp" date="2023-05-03" typecodes="ST" codenum="G2931K" picturebasename=""> <recipelines> <recipeline material="Ferro Frit 3195" amount="25.000" tolerance=""/> <recipeline material="Ferro Frit 3134" amount="33.000" tolerance=""/> <recipeline material="EPK" amount="20.000" tolerance=""/> <recipeline material="Ferro Frit 3249" amount="10.000" tolerance=""/> <recipeline material="Ferro Frit 3110" amount="7.000" tolerance=""/> </recipelines> </recipe> </recipes> Born: 2006-03-16, Modified: 2023-05-03 20:54:14 |
Cone 05+ Expansion Adjustable Gloss Base
Total:100.00
Notes *Although similar to the previous G1916M, this recipe provides greater thermal expansion adjustability. 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). The frits in this recipe are common (the 3249 less so but it deserves to be common because of its utility). We adjusted this in a later version, G1916QL1, it employs a kaolin for better clarity and more frit 3249 for glaze fit on more bodies. 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 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. 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 ![]() Has survived for a year without crazing. 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. G1916Q applied thickly on L215 fired cone 04 ![]() No crazing after 2 months. G1916Q on L4170 cone 04 ![]() Thin application is clearly the way to get the best transparent. The glaze eventually craze where application is thicker. XML (to paste into Insight) <?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Cone 05+ Expansion Adjustable Gloss Base" id="56565" key="vEnWWoco" date="2023-10-31" 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=""/> </recipelines> </recipe> </recipes> Born: 2014-03-04, Modified: 2023-10-31 22:20:07 |
Cone 04+ UltraClear Glossy Base
Total:1,025.00 Auto Unity Formula
Notes *We developed this for cone 06-04 to fit many clay bodies (without crazing), melt well at cone 05 and produce a more transparent glaze (rather than the amber of G2931K and G1916Q). The frit F-524 in this recipe is less common among potters but common in industry, it is high quality. We later adjusted this recipe to produce variations (e.g. with whiter kaolin, more of the frit F-69 to get a lower thermal expansion). Pictures G3879 Clear glaze on Plainsman L211 - Cone 04 ![]() Glossy, crystal clear, no crazing! And this is a 42 mesh body containing zero talc. Melt fluidity comparison with #1 commercial clear ![]() We tested half-a-dozen commercial clears and found G3859 to be the best all-around one. This one has a very similar melt fluidity. G3879 on Plainsman L210, L215 at cone 04 ![]() These are 42 mesh low fire bodies. They normally have issues with pinholing but using this glaze the results are stunning. The L210 contains no talc, the L215 has 10%, yet this glaze does not craze on either one (over time it shivers on the L215). G3879 on SIAL 25F, Plainsman J2, L4170 TerraCotta ![]() These are very different bodies. The leftmost contains talc to raise the thermal expanison to help prevent crazing with commercial glazes. The center one contains nepheline syenite (for the same purpose). The terra cotta on the right is just Redart and ball clay. This glaze fits are all three! Sial 10F, 25F with G3879 clear glaze at cone 03 ![]() Tile like these were done on a variety of bodies and fired at different temperatures. After a year: 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. G3879 with 5% Tin Oxide on SIAL 10F ![]() When mixing Tin (as an opacifer), it is very important to mix it well. The one on the left was mixed poorly (at high speed with my propeller mixer but not for long enough). The one on the right was mixed much better and so produces better opacity. Tin is expensive so this is important. G3879 on Plainsman Buffstone - cone 03 ![]() Buffstone is an entry-level low-price body not intended to fit commercial glazes. Yet this glaze fits at cone 03 (still fitting after a year)! And without any surface defects. G3879 Zircon White on SIAL 25F, 10F - cone 03 ![]() 10% zircopax has been added. It is melting well so the percentage could be increased for great opacity on red burning bodies. G3879 at cone 1 on SIAL 10F, 25F ![]() Crystal clear, no running. Perfect! GBMF test on G3879 at cone 1 ![]() It is not running and flowing nearly as much as expected. The melt surface tension holds it in place, so it should be able to fire to cone 2 and beyond. G3879 on terra cotta at cone 04, 02, 1 ![]() This is on the L4170 body, it is a lighter firing product, 25F, from SIAL. After use on various bodies, it was clear that fit at cone 03 is better than at 04 and much better than 06. G1916M, G3879, G2931K on L215 - Thick ![]() Thickly applied encourage poor fit to show up. L213 with G3879 glaze at cone 04 ![]() Survived 325F:IceWater test with almost no crazing. However there was a little shivering on the rim after a month. Another mug had no crazing on the inside after several months. G3879 on L4115J2 buff body at cone 04 ![]() Glaze is ultra clear. G3879 on SIAL 10F at cone 02 ![]() No crazing after several months. Flawless service. Variations B - Tin White XML (to paste into Insight) <?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Cone 04+ UltraClear Glossy Base" id="154451" key="2qsZ5kFK" date="2023-06-16" codenum="G3879"> <recipelines> <recipeline material="Fusion Frit F-524" amount="850.000" tolerance=""/> <recipeline material="Fusion Frit F-69" amount="40.000" tolerance=""/> <recipeline material="EPK" amount="90.000" tolerance=""/> <recipeline material="Silica" amount="45.000" tolerance=""/> </recipelines> </recipe> </recipes> Born: 2019-04-15, Modified: 2023-06-16 11:32:20 |