Cornwall Stone Substitute recipe

Share from Insight-live.com (Lab Documentation and Calculation System) by Digitalfire. https://digitalfire.com

Cornwall Stone was similar to feldspars in chemistry thus it makes sense that a mix of other feldspars and materials should be able to duplicate the chemistry (and thus melting behavior)


Cornwall Stone Average Analysis

Code #

L3619

Materials Amt
Cornwall Stone 100.000

Total:100.00

Auto Unity Formula

CaO 0.24
MgO 0.03
K2O 0.34
Na2O 0.40
(KNaO) 0.73
TiO2 0.01
Al2O3 1.19
SiO2 9.11

Ratios

Si:Al: 7.7:1
R2O:RO: 0.7:0.3

Expansion

6.6 (Molar:6.2)

Notes

*Powder is grey buff. This is the material sold for many years until Oct 2011.

Flow test at cone 6 and 8 showed no melting. At cone 11 it has just barely begun to flow. The melt character is more similar to L3617 (our substitute) than to other recipes and substitutes we have tried.

Pictures

L3618 new Cornwall Stone vs L3617, L3619

Left: L3618 original Cornwall Stone (2011 shipment)
Second from left: L3617 Cornwall Stone substitute recipe
Third from left: Old Cornwall Stone (pre 2011).
Far right: H&G substitute (marketed ~2012)

Fired at cone 11. Without a frit addition not much movement.

Cornwall Stone substitute vs real material at cone 6

Flow test of L3617 Cornwall Stone substitute + 20% Frit 3134 compared to real Cornwall stone (also plus frit)

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Cornwall Stone Average Analysis" id="66271" key="SWX7APcL" date="2023-06-10" codenum="L3619" picturebasename=""> <recipelines> <recipeline material="Cornwall Stone" amount="100.000" tolerance=""/> </recipelines> </recipe> </recipes>

Born: 2011-10-15, Modified: 2023-06-10 09:54:05

Cornwall Stone substitute #2

Code #

L3617

Materials Amt
Custer Feldspar 30.000
Nepheline Syenite 24.450
Dolomite 0.560
Wollastonite 2.800
Pioneer Kaolin 12.730
Silica 29.450

Total:99.99

Auto Unity Formula

CaO 0.24
MgO 0.03
K2O 0.33
Na2O 0.40
(KNaO) 0.73
TiO2 0.02
Al2O3 1.15
SiO2 8.99

Ratios

Si:Al: 7.8:1
R2O:RO: 0.7:0.3

Expansion

6.6 (Molar:6.2)

LOI

2.3

Notes

*The matching of Al2O3 and SiO2 oxides is not precise, when this was done originally in desktop Insight TiO2 was included in unity but in Insight-live it is not.

This recipe has been used for many years and has served well. Other Cornwall substitutes are available, there is lots of opportunity to compare this with them (a melt fluidity test is the most revealing).

Of course, this is not an exact science, but from a theoretical view point a couple of things can be mentioned. In production the tiny amount of dolomite is not really needed. Also, since this has an LOI of 2.4, that means 2.4% more should be substituted for the amount of original Cornwall Stone called for in recipes (again, if only a small amount is used in a recipe this would not be a big deal).

Pictures

Cornwall Stone substitute vs real material at cone 6

Flow test of L3617 Cornwall Stone substitute + 20% Frit 3134 compared to real Cornwall stone (also plus frit)

L3618 new Cornwall Stone vs L3617, L3619

Left: L3618 original Cornwall Stone (2011 shipment)
Second from left: L3617 Cornwall Stone substitute recipe
Third from left: Old Cornwall Stone (pre 2011).
Far right: H&G substitute (marketed ~2012)

Fired at cone 11. Without a frit addition not much movement.

XML (to paste into Insight)

<?xml version="1.0"?> <recipes version="1.0" encoding="UTF-8"> <recipe name="Cornwall Stone substitute #2" id="66269" key="dp85M2jk" date="2023-06-10" codenum="L3617" picturebasename=""> <recipelines> <recipeline material="Custer Feldspar" amount="30.000" tolerance=""/> <recipeline material="Nepheline Syenite" amount="24.450" tolerance=""/> <recipeline material="Dolomite" amount="0.560" tolerance=""/> <recipeline material="Wollastonite" amount="2.800" tolerance=""/> <recipeline material="Pioneer Kaolin" amount="12.730" tolerance=""/> <recipeline material="Silica" amount="29.450" tolerance=""/> </recipelines> </recipe> </recipes>

Born: 2011-10-14, Modified: 2023-06-10 12:10:50