Fixing Cone 6 Leaches Clear - Crazing

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Leach's Satin Clear Original

Code #

G2941A

Materials Amt
Custer Feldspar 21.700
Whiting 21.700
Silica 21.700
EPK 21.700
Ferro Frit 3124 13.200

Total:100.00

Auto Unity Formula

CaO 0.84
K2O 0.08
Na2O 0.08
(KNaO) 0.16
B2O3 0.09
Al2O3 0.43
SiO2 2.96

Si:Al Ratio

7.0:1

SiB:Al Ratio

7.2:1

Calculated
Expansion

7.2

LOI

12.8

Cost

54.69 per kg

Notes

This is crazing on Laguna B-mix. Neither the clay or glaze are at fault, they are simply incompatible. Still, 20% feldspar sourcing lots of KNaO plus extra KNaO coming from a frit certainly makes crazing less than a surprise.

Concerns: It is melting enough, it has low B2O3. Dangers are cutlery marking and leaching.

Since this is a silky matte, it will be able to accept MgO and can afford to give up KNaO, so it will be easy to reduce the thermal expansion.

It might be wise to consider using the base matte at http://plainsmanclays.com/index.php?menupath=62
It can be tuned by adding glossy glaze, giving alot of control over the degree of matteness. Matteness is a fragile mechanism that needs close control and assure a compromise between functionality and appearance.

URLs

A good adjustable base matte recipe

Pictures

Leaches clear on BMix - Crazing

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Leach's Satin Clear Original" id="61955" key="3EFTzAdn" date="2014-10-24" codenum="G2941A" email="j_johnsrud@hotmail.com"> <recipelines> <recipeline material="Custer Feldspar" amount="21.700"/> <recipeline material="Whiting" amount="21.700"/> <recipeline material="Silica" amount="21.700"/> <recipeline material="EPK" amount="21.700"/> <recipeline material="Ferro Frit 3124" amount="13.200"/> </recipelines> </recipe> </recipes>

Born: 2014-10-14, Modified: 2014-10-24 22:44:35

Leach's Satin Clear - Craze fix

Code #

G2941C

Materials Amt
Custer Feldspar 21.485
Whiting 21.485
Silica 22.475
EPK 21.485
Ferro Frit 3124 5.149
Ferro Frit 3249 7.921

Total:100.00

Auto Unity Formula

CaO 0.78
MgO 0.08
K2O 0.08
Na2O 0.05
(KNaO) 0.13
B2O3 0.14
Al2O3 0.43
SiO2 2.96

Si:Al Ratio

6.8:1

SiB:Al Ratio

7.1:1

Calculated
Expansion

6.8

LOI

12.7

Cost

56.63 per kg

Notes

I orginally tried incorporating MgO using Talc. But this time I just split the frit with Ferro Frit 3249, it is a much better source of MgO and brings more B23O3 (just what I want). 3249 is a super-low expansion frit. Only small changes were needed to match up oxide levels disrupted by its introduction. The fired result look identical on the flow tester. But if it is a little to glossy, Al2O3 levels can be raised to tune it (since it is melting a little better).

Another helpful change that could be made is sourcing CaO using Wollastonite instead of calcium carbonate.

Pictures

Leach's Clear crazing adjustment

This substitutes MgO for some of the CaO and KNaO. It also adds a little more B2O3 for better melting. This melts just as good or better and appears to have about the same surface gloss. It would be a little more matte by raising the Al2O3, this would drive the expansion down even further.

Leach's clear and craze adjustment

3mm thick x 15mm square samples fired on a porcelain tile.
Left: Original
Right: Adjustment.
The surface is iddentical on this samples.

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Leach's Satin Clear - Craze fix" id="61966" key="cT6jtcw7" date="2014-10-23" codenum="G2941C" email="j_johnsrud@hotmail.com"> <recipelines> <recipeline material="Custer Feldspar" amount="21.485"/> <recipeline material="Whiting" amount="21.485"/> <recipeline material="Silica" amount="22.475"/> <recipeline material="EPK" amount="21.485"/> <recipeline material="Ferro Frit 3124" amount="5.149"/> <recipeline material="Ferro Frit 3249" amount="7.921"/> </recipelines> </recipe> </recipes>

Born: 2014-10-16, Modified: 2014-10-23 13:56:51