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Worthington Clear with Ulexite:PbO

Code #

G2931E

Materials Amt
EPK 25.100 22.86%
Silica 10.600 9.65%
Ulexite 26.500 24.13%
Ferro Frit 3249 16.900 15.39%
Wollastonite 15.500 14.12%
Nepheline Syenite 5.200 4.74%
Frit B300 10.000 9.11%

Total:109.80

Auto Unity Formula

CaO 0.63
MgO 0.15
K2O 0.01
Na2O 0.12
(KNaO) 0.13
PbO 0.09
B2O3 0.69
Al2O3 0.38
SiO2 2.15

Ratios

Si:Al: 5.6:1
SiB:Al: 7.4:1
R2O:RO: 0.1:0.9

Expansion

6.6 (Molar:6.5)

LOI

12.0

Cost

0.00 per kg

Notes

*The adds lead to the Ulexite version of Worthington clear (G2931B). This is more crystal clear, it fires very well on various terra cotta clays. The slurry is also outstanding, it gels well (in contrast to the gelled mess of the Gerstley Borate version), applies well and does not settle at all (a whole new experience for long time Worthington Clear sufferers!).

Shivers a little on Terrastone test, so should increase KNaO at the expense of CaO or MgO.

Pictures

16x image of entrained bubbles

These are in the PbO enhanced Ulexite version of Worthington low temperature clear.

Left B, right E

The little extra lead frit gives it quite a bit better gloss.

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.

Ulexite PbO clear at cone 04

These are various different terra cotta clays (also a low fire white-buff fritted stoneware). All are fired with a drop-100F-and-soak firing. Fits is good on all except a fritted terra cotta stoneware where it is shivering slightly. All survived a boil:ice test.

Terratone test with G2931E glaze

A little shivering after boil:ice test.

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Worthington Clear with Ulexite:PbO" id="75220" key="hibaB3oX" date="2015-06-29" codenum="G2931E" picturebasename=""> <recipelines> <recipeline material="EPK" amount="25.100" tolerance=""/> <recipeline material="Silica" amount="10.600" tolerance=""/> <recipeline material="Ulexite" amount="26.500" tolerance=""/> <recipeline material="Ferro Frit 3249" amount="16.900" tolerance=""/> <recipeline material="Wollastonite" amount="15.500" tolerance=""/> <recipeline material="Nepheline Syenite" amount="5.200" tolerance=""/> <recipeline material="Frit B300" amount="10.000" tolerance=""/> </recipelines> </recipe> </recipes>

Born: 2014-03-19, Modified: 2015-06-29 12:30:48

Firing Schedule Name

Cone 04 Glaze (drop-100-soak)

Degrees (Fahrenheit or Celcius)

F

Schedule Type

Rate

Start Time and Temperature

7:00 am (no temperature specified)

Program

Step Degrees/Hr Temperature
Monitor
Hold
Time
Accumulated
hrs:min
Time Note
1 400 240 60 1:36 8:36 am
2 400 1805 5:30 12:30 pm
3 108 1905 10 6:25 1:25 pm
4 108 1805 30 7:20 2:20 pm

Notes

Rather than holding for a longer time at the top temperature, this schedule follows the custom of cooling 100 degrees and holding there for half an hour. The idea of this is that reactions that generate gases that cause pinholes and blisters will have stopped.

Joe: April 7/20 Program 19 in ConeArt test kiln
R1. 150 - 250 Hold 30
R2. 450 - 1815 Hold 0
R3. 108 - 1920 Hold 15
R4. 999 - 1820 Hold 30 / Off
This was done for low temperature sample board side disc glazed samples. Glazes turned out very nice and smooth.
Self supporting cone 04 down past 90 degrees orton cone template and barely touching shelf, but not deformed yet. So, perfect firing.

Pictures

Joe's notes April 7/20