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El Cornwall Stone es usado en cerámica como fuente de óxidos fundentes en la pasta y esmaltes. Se asemeja al feldespato. Dado que puede sufrir metamorfismo, en realidad hay diversas clases en cuanto a composición dependiendo del grado de alteración. Los azules y púrpuras (menos alterados) contiene más K2O y Na2O, y flúor que los blancos.

Conocido de diversas formas como China stone, Cornwall stone, Cornish stone, Pegmatita, Graven. Gowen, Manx stone, Meldon stone, Growan, Petunste, Amakusa,


Tony Hansen[]

Tony, propone para el cálculo del sustituto realizar una media de las distintas composiciones existente en la bibliografía.

Receta para sustituir Cornwall stone. [1]

Feldespato Custer..... 15.00
Nefelina sienita... 22.00
Caolín.............. 6.00
Sílice.............. 20.50
Talco................ 1.50
-------
65.00


Ron Roy[]

Ron's Seger molecular unity formula for Cornwall Stone based on H&G's analysis.[2]

CORN STN............ 100.00


FORMULA & ANALYSIS[]

  • CaO........ .26 2.02%
  • MgO........
  • K2O........ .29 3.74%
  • Na2O....... .44 3.74%
  • Fe2O3...... .01 .14%
  • TIO2....... .01 .07%
  • AL2O3...... 1.16 16.14%
  • SiO2....... 9.03 73.65%
  • P2O5....... .03 .51%
  • RATIO 7.76
  • EXPAN 399.42
  • WEIGHT 735.81

Ron's calculated sub (untested) for his Cornwall Stone (untested) based on the unity formula - note higher expansion than the original.

  • G 200 SPAR.......... 59.00
  • EPK................. 12.50
  • SILICA.............. 26.00
  • WHITING............. 2.50


  • FORMULA & ANALYSIS
  • CaO........ .26 1.93%
  • MgO........ .00 .02%
  • K2O........ .52 6.54%
  • Na2O....... .22 1.84%
  • Fe2O3...... .01 .16%
  • TIO2....... .00 .04%
  • AL2O3...... 1.17 16.07%
  • SiO2........... 9.12 73.39
  • P2O5....... .00 .02%
  • RATIO 7.77
  • EXPAN 424.57
  • WEIGHT 746.03

Rons duplication based on the calculated percent of oxides in the fired material. Note the calculated expansion in this last one compares better with the H&G analysis but there is a greater difference in the oxides present when you look at the unity formula - can someone explain the difference to me?

I do know there are some people in industry that use the fired % analysis instead of the molecular formula for problem solving - anyone have a clue as to why?

  • G 200 SPAR.......... 53.00
  • EPK................. 15.50
  • SILICA.............. 28.50
  • WHITING............. 3.00
---
100.00
  • FORMULA & ANALYSIS
  • CaO........ .30 2.18%
  • MgO........ .01 .03%
  • K2O........ .49 5.94%
  • Na2O....... .21 1.66%
  • Fe2O3...... .01 .18%
  • TIO2....... .00 .05%
  • AL2O3...... 1.23 16.20%
  • SiO2....... 9.50 73.74%
  • P2O5....... .00 .02%
  • RATIO 7.74
  • EXPAN 398.48
  • WEIGHT 772.69




GlazeChem[]

Fuente: [3]

For: 1.00 Cornwall Stone Sub:

  • 0.65 Custer feldspar (27)
  • 0.04 Whiting
  • 0.13 Kaolin
  • 0.22 Silica

For: 1.00 Cornwall Stone Sub:

  • 0.65 Custer feldspar (28)
  • 0.04 Whiting
  • 0.11 Calcined kaolin
  • 0.22 Silica

For: 1.00 Cornwall Stone Sub:

  • 0.63 Custer feldspar (29)
  • 0.04 Whiting
  • 0.05 Alumina
  • 0.30 Silica

For: 1.00 Cornwall Stone Sub:

  • 0.61 Custer feldspar (30)
  • 0.04 Whiting
  • 0.09 Alumina hydrate
  • 0.30 Silica

For: 1.00 Cornwall Stone Sub:

  • 0.48 Nepheline syenite (31)
  • 0.04 Whiting
  • 0.12 Kaolin
  • 0.38 Silica

For: 1.00 Cornwall Stone Sub:

  • 0.49 Nepheline syenite (32)
  • 0.05 Whiting
  • 0.10 Calcined kaolin
  • 0.38 Silica

For: 1.00 Cornwall Stone Sub:

  • 0.48 Nepheline syenite (33)
  • 0.05 Whiting
  • 0.05 Alumina
  • 0.44 Silica

For: 1.00 Cornwall Stone Sub:

  • 0.48 Nepheline syenite (34)
  • 0.04 Whiting
  • 0.07 Alumina hydrate
  • 0.44 Silica

For: 1.00 Cornwall Stone Sub:

  • 0.67 Kona F-4 (35)
  • 0.02 Whiting
  • 0.07 Kaolin
  • 0.25 Silica

For: 1.00 Cornwall Stone Sub:

0.66 Kona F-4 (36)

  • 0.02 Whiting
  • 0.06 Calcined kaolin
  • 0.26 Silica

For: 1.00 Cornwall Stone Sub:

  • 0.66 Kona F-4 (37)
  • 0.02 Whiting
  • 0.03 Alumina
  • 0.29 Silica

For: 1.00 Cornwall Stone Sub:

  • 0.65 Kona F-4 (38)
  • 0.02 Whiting
  • 0.04 Alumina hydrate
  • 0.29 Silica

For: 1.00 Cornwall Stone Sub:

  • 0.67 G-200 feldspar
  • 0.04 Whiting
  • 0.09 Kaolin
  • 0.25 Silica

For: 1.00 Cornwall Stone Sub:

  • 0.67 G-200 feldspar (40)
  • 0.03 Whiting
  • 0.08 Calcined kaolin
  • 0.25 Silica

For: 1.00 Cornwall Stone Sub:

  • 0.66 G-200 feldspar (41)
  • 0.03 Whiting
  • 0.04 Alumina
  • 0.29 Silica

For: 1.00 Cornwall Stone Sub:

  • 0.67 G-200 feldspar (42)
  • 0.03 Whiting
  • 0.05 Alumina
  • 0.29 Silica


Books-aj.svg aj ashton 01f Referencias[]

  1. Substituting Cornwall Stone. Tony Hansen en Digitalfire Ceramics.
  2. cornwall stone substitution. Ron Roy en ClayArt
  3. GlazeChem 2.1


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