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Week 38

 

  1. The nineteenth century chemist Herman Seger divided part of the oxides in glazes into three groups:______________________, neutral oxides, and acid oxides.

    1. reduction oxides (glass formers)

    2. oxidation oxides (bases)

    3. basic oxides (fluxes)

    4. all of the above

  2. These colors are only visible in an oxidation atmosphere. Up to 10220F. there will be no color inside the kiln. . .. . . . . becomes deep red at 14540F.. . . . . at around 21560F. it is a pale orange. . . At 23360F. the color changes from pale yellow to___________________. . . . . . .

    1. pure white

    2. bright orange

    3. pale white

    4. yellowish white

  3. Glazing with a Brush. . . Before glazing gently wash the piece to remove all traces of dust. The water will also keep __________________________.

    1. the glaze from being absorbed too quickly. . .

    2. the dust from re-adhering to the pot. . ..

    3. the pot from slipping out your grip. . . .

    4. fingers prints off of the ware. . . .

  4. _____________________ glazes are transparent and shiny and are produced by a saturation of iron oxide with a very low alumina content. The glaze crystallizes on cooling, producing shiny reddish or golden brown crystals. The percentage of iron is from 3 to 15 percent; the percentage is important because too much iron turns the glaze opaque or cloudy.

    1. Scotch Topaz

    2. Celedon

    3. Raku

    4. Oxblood

 

This weeks questions come from Ceramics Class: Glazing Techniques, Joaquim Chavarria, c 1998, 1999 Watson Guptill Publications, NY NY

 

Note from Pres: This book, even though small is a powerhouse of ideas for beginners, or those teaching beginners. You will be seeing more from other books in the Ceramics Class series.

 

Answers:

  1. 3. basic oxides-Seger divided part of the oxides into three groups: basic oxides (fluxes), neutral oxides, and acid oxides.

  2. 4. yellowish white-These colors are only visible in an oxidation atmosphere. Up to 500°C (l022°F), there will be no color inside the kiln. Between 550 and 600°C (l022—lll2°F), the kiln will look dull red, which deepens-between 600 and 700°C (1112—l292°F), and finally becomes deep red around 790°C (l454°F). From this point on the deep red begins to turn cherry red, a color that becomes fully developed at 880°C (l6l6°F). At 980°C (l796°F), it is a paler cherry, tending toward orange, which turns brilliant between 1000 and l080°C (l83Z—l976°F). At around ll80°C (2l56°F) it is pale orange and becomes paler still at l250°C (2282°F). At l280°C (2336°F) the color changes from pale yellow to yellowish white. Between 1300 and l350°C (2342-2462°F) it is yellowish white, and it becomes a dazzling white at l380°C (25l6°F). At around l480—l500°C (2696—2732°F) the color is a brilliant, dazzling white with a bluish haze.

  3. 1. the glaze from being absorbed too quickly. . .Before glazing, gently wash the piece to remove all traces of dust. The water will also keep the bisque-fired ware from absorbing the glaze too quickly and will prevent a wide brush from leaving too thick an application of glaze. To avoid the bisque fired clay absorbing the glaze too quickly (thus resulting in uneven coverage), it is a good idea to apply a first layer or wash with a fairly watery glaze solution.

  4. 1. Scotch Topaz-These glazes take their name from their similarity to a rock of the same name, a dark yellow quartz with fine layers of embedded golden mica. The earliest known glazes of this type originated in ancient China. Scotch topaz glazes are transparent and shiny and are produced by a saturation of iron oxide with a very low alumina content. The glaze crystallizes on cooling, producing shiny reddish or golden brown crystals. The percentage of iron oxide ranges from 3 to 15 percent the percentage is important because too much oxide turns the glaze opaque or cloudy. The flux may be lead, or alkaline materials such as sodium or potassium.

 

 

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