Share from Insight-live.com (Lab Documentation and Calculation System) by Digitalfire.
Zero3 Ulexite-based glaze, engobe and firing schedule
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.
Low Fire Clear Glaze Comparison
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.
Deb's Clear Cone 04-02
Auto Unity Formula
*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.
XML (to paste into Insight)
<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Deb's Clear Cone 04-02" id="70214" key="6PJEKsEC" 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>
Worthington Cone 06-2 Clear
Gelling, High LOI, Gerstley Borate difficult to sub, High Boron
Auto Unity Formula
*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).
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. Left: The original Worthington fluid melt clear glaze recipe. There are clusters of tiny bubbles and many large. Center: A glaze of the same chemistry but sourcing its boron from Ulexite instead. Notice the lack of tiny bubbles. This fires pretty well identical to the original but has much better slurry properties. Right: Center with with a 10% addition of lead bisilicate frit. This fires more glossy than either of the other two. Its thermal expansion is also likely lower.
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
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="r2GQz3Xr" date="2017-09-05" 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>
Zero3 K Cone 03 Transparent Glaze
Auto Unity Formula
*This recipe improves the popular Worthington Gerstley-Borate-based low fire clear recipe. It targets cone 03 to work best on Zero3 stoneware and porcelain. However many low fire bodies are dramatically stronger when fired to cone 03 with this (or one of its thermal expansion variants L & H). And the vast majority of commercial glaze products will fire easily to this temperature. If you absolutely must fire lower, to cone 06 or 04, then use the G1216Q recipe instead.
Batch Ticket Notes
These notes were entered in the notes panel under "Batch Ticket Notes"
G2931K on Zero3 Stoneware
Fired cone 03. Body is Zero3 stoneware. Surface is perfect, even where thick. Ultra clear. Survived three boil:ice cycles and one 300F:ice cycle without crazing.
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. The K is slightly smoother, tiny dimples in the surface are fewer. It is also applied thicker.
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. We subjected all of them to a 300F:IceWater thermal shock. Buffstone crazed on all of them. L215 and L212 Cone 04 crazed. L213 was good but later the glaze was found to be under excessive compression, subject to shivering over underglazes. At cone 02 there are some dimples and defects.
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. The material in photo was screened out once again after the 3 month time lapse, (80 mesh once again). The largest balls are approx. 2.5 mm. in diameter, and when these particles were screened out, and still perhaps slightly wet?, they were quite easy to break in half with your fingernail.
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="4YP5er3g" date="2020-12-02" typecodes="ST" codenum="G2931K" picturebasename=""> <recipelines> <recipeline material="Ferro Frit 3195" amount="25.000" tolerance="" unitabbr="KG"/> <recipeline material="Ferro Frit 3134" amount="33.000" tolerance="" unitabbr="KG"/> <recipeline material="EPK" amount="20.000" tolerance="" unitabbr="KG"/> <recipeline material="Ferro Frit 3249" amount="10.000" unitabbr="KG"/> <recipeline material="Ferro Frit 3110" amount="7.000" unitabbr="KG"/> </recipelines> </recipe> </recipes>
Cone 05+ Expansion Adjustable Gloss Base
*This recipe provides great thermal expansion adjustability 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). The frits in this recipe are common (the 3249 less so but it deserves to be common because of its utility).
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 05+ Expansion Adjustable Gloss Base" id="56565" key="wsy8bM6H" date="2021-09-11" 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>
Cone 04+ UltraClear Glossy Base
Auto Unity Formula
*I developed this for cone 04 to fit as many clay bodies (without crazing) as possible (my Zero3 clear works well on specific bodies but does not melt enough at cone 04 and its thermal expansion is too high to fit some bodies). The frits in this recipe are less common among potters but common in industry.
Mike ODonnell and Fusion Frits says many customers use F280 and F38. He suggested F5 might be most similar to this. But I found that F524 was by far the closest.
If you want to make this into a air brushing glaze, which actually applies better to the sample board side discs, the glaze must be screened 200 mesh and then specific gravity adjusted to 1.40 and at this S.G. the powder to water ratio would be approx. 54% glaze powder and 46% water content.
Joe: Made some this glaze up in March of 2020 and checked June 2020 ( 3 months later), and glaze has hard panned quite badly, but was able to remix with a little effort. The next day it was easier to remix. The Specific Gravity was adjusted to 1.50 and a moisture content was taken at this point in time and found to be 54.25% glaze powder and 45.75% water content. This glaze was used on the low temperature sample boards for the L215 "bottom" side samples, as well as the L210 "top" side samples. The samples were bisqued in the cone 06-05 range and glaze fired at the same temperature more or less.
Joe: June 4/21
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).
G3878 has a high surface tension
As can be seen in the way it has melted here.
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! After a year, both the 25F and J2 were difficult to break, very strong!
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: Sial 10F Cone 02: No crazing Cone 04: Moderate crazing over time Cone 06: Severe crazing Cone 03: No crazing Sial 25F Cone 1: No crazing Cone 03: No crazing Cone 04: Crazing badly L215 Cone 04: No crazing L210 Cone 04: No crazing L212 Cone 04: Crazing Cone 1: No crazing L213 Cone 04: No crazing
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. This was not crazed after a year (cone 03).
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. At cone 04 it does craze over time.
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. Clearly, as shivering and cracking demonstrate, G3879 is under excessive compressive on L215. The other two are not showing any issues (other than heavy bubbling because of the thickness). G1216M is a blend of 3124/3124 with kaolin. G2931K is the Zero3 clear.
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. It was refired at cone 022 to apply a decal. It was 325F to icewater tested without crazing. It was waterlogged (the bottom is bare clay) and then put in a microwave for two minutes. Despite getting incredibly hot it did not fracture or craze! Was still fitting after a year+.
G3879 on SIAL 10F at cone 02
No crazing after several months. Flawless service.
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="pgDLcx36" date="2021-09-11" 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>