Understanding Glaze Terms

Glaze Categories

I wish someone would have broken it down like this for me when I first started out working with clay.

Glaze CategoryGlaze Descriptions
Raw GlazesMade from raw materials and require thorough mixing.
Fritted GlazesMade from frits, which are pre-melted glazes. Easier to use but can be expensive.
Commercial GlazesPre-made and come in liquid or dry form. Convenient but less customizable.

Raw Glazes


Raw glazes are made from raw materials like feldspar, talc, and silica. These materials are weighed and mixed together to form a glaze.


  • Customizable: Allows for a high degree of customization.
  • Complexity: Requires a thorough understanding of each raw material’s properties.
  • Labor-Intensive: Mixing and sieving are generally required.
  1. Highly customizable.
  2. Can be cost-effective if raw materials are sourced cheaply.
  1. Requires a deep understanding of materials and chemistry.
  2. Time-consuming to prepare.

Fritted Glazes


Fritted glazes are made from frits, which are pre-melted glazes. They are generally easier to use than raw glazes.


  • Ease of Use: Generally easier and quicker to prepare than raw glazes.
  • Consistency: Offers a more consistent result.
  • Cost: Can be more expensive due to the pre-melting process.
  1. Easier to use for beginners.
  2. Consistent results.
  1. Less customizable.
  2. Can be more expensive.

Commercial Glazes


Commercial glazes are pre-made glazes that come in either liquid or dry form. They are the most convenient but offer the least amount of customization.


  • Convenience: Extremely easy to use.
  • Variety: Available in a wide range of colors and textures.
  • Cost: Generally more expensive due to convenience and packaging.
  1. Best for hobbyists or those new to pottery.
  2. Wide variety of options.
  1. Limited customization.
  2. Higher cost compared to making your own glazes.

Important Terms and Definitions

Understanding these terms and definitions is crucial for anyone involved in the art of pottery, as they form the basis for the creation, application, and successful firing of glazes.

Glaze TermDefinition
GlazeA layer of material applied to ceramics to form a glass-like surface.
FiringThe process of heating ceramics in a kiln to harden and mature the glaze.
KilnA furnace used for firing ceramics.
ConeA unit of measurement for kiln temperature.
Maturing PointThe temperature at which a glaze becomes fully functional.
FluxA material that lowers the melting point of another material.
SilicaThe glass former in a glaze.
AluminaAdds stiffness to the molten glaze.
OxidesAdd color and other qualities to the glaze.



A glaze is a layer of material that is applied to ceramics to create a glass-like surface after firing.


  • Composition: Typically made of silica, alumina, and various fluxes.
  • Purpose: Enhances the aesthetic and functional properties of ceramics.
  1. Adds aesthetic value to pottery.
  2. Increases durability and functionality.
  1. Requires precise application and firing.
  2. May react differently with various clay bodies.



Firing is the process of heating ceramics in a kiln to harden and mature the glaze.


  • Temperature: Varies depending on the type of clay and glaze used.
  • Duration: Can last from several hours to days.
  1. Hardens and matures the clay and glaze.
  2. Finalizes the ceramic piece.
  1. Requires a kiln, which can be expensive.
  2. Risk of defects like cracks or warping.



A kiln is a furnace used for firing ceramics.


  • Types: Electric, gas, and wood-fired are common types.
  • Temperature Range: Can reach temperatures over 2300°F (1260°C).
  1. Essential for ceramic making.
  2. Available in various sizes and types.
  1. Can be expensive to purchase and operate.
  2. Requires proper ventilation and safety measures.



A cone is a unit of measurement used to gauge the temperature inside a kiln during firing.


  • Material: Made of ceramic material that melts at specific temperatures.
  • Usage: Placed inside the kiln to monitor firing conditions.
  1. Provides an accurate measure of kiln temperature.
  2. Helps in achieving consistent firing results.
  1. Consumable; needs to be replaced after each firing.
  2. Requires proper placement inside the kiln for accurate readings.

Maturing Point


The maturing point is the temperature at which a glaze becomes fully functional and achieves its desired properties.


  • Critical: Determines the success of the glaze.
  • Variable: Different for each type of glaze.
  1. Achieving the maturing point ensures a successful glaze.
  2. Helps in planning the firing schedule.
  1. Requires precise control of kiln temperature.
  2. Miscalculating can lead to glaze defects.

Flux, Silica, Alumina, and Oxides


  • Flux: A material that lowers the melting point of another material in the glaze.
  • Silica: The primary glass former in a glaze.
  • Alumina: Adds stiffness to the molten glaze.
  • Oxides: Add color and other qualities to the glaze.


  • Interdependent: The balance between these components affects the final glaze properties.
  1. Allows for a wide range of glaze characteristics.
  2. Essential for creating unique glazes.
  1. Requires a deep understanding of each component’s role.
  2. Imbalance can lead to glaze defects.

Glaze Concepts

Understanding these glaze concepts is essential for anyone looking to master the art of pottery. They not only influence the aesthetic outcome but also the functional integrity of the ceramic pieces.

Glaze ConceptExplanation
Glaze FitThe compatibility between the clay body and the glaze.
CrazingFine cracks in the glaze surface, usually due to poor glaze fit.
ShiveringWhen the glaze peels off the clay body, also due to poor glaze fit.
Glaze LayeringApplying multiple layers of different glazes for varied effects.
Glaze TestingThe practice of applying a glaze to test tiles and firing them to see the results.

Glaze Fit


Glaze fit refers to the compatibility between the clay body and the glaze applied to it.


  • Compatibility: Ensures that the glaze and clay body expand and contract at similar rates.
  • Importance: Crucial for the longevity and functionality of the finished piece.
  1. Achieving good glaze fit prevents common defects like crazing and shivering.
  2. Enhances the durability of the ceramic piece.
  1. Requires testing and experimentation.
  2. May limit the choice of glazes for a particular clay body.



Crazing is the appearance of fine cracks on the surface of the glaze.


  • Cause: Usually due to a poor fit between the glaze and the clay body.
  • Appearance: Looks like a spiderweb of fine lines on the glazed surface.
  1. Sometimes used intentionally for aesthetic effects.
  1. Weakens the structural integrity of the ceramic piece.
  2. May harbor bacteria, making the piece unsuitable for food use.



Shivering refers to the phenomenon where the glaze peels off from the clay body.


  • Cause: Also due to poor glaze fit, but in this case, the glaze is under too much tension.
  • Risks: Can result in sharp, hazardous edges.
  1. Rarely, if ever, considered a positive attribute.
  1. Renders the ceramic piece unusable.
  2. Can be dangerous due to the sharp edges of peeled-off glaze.

Glaze Layering


Glaze layering involves applying multiple layers of different glazes to achieve varied effects.


  • Technique: Requires skillful application of different glazes.
  • Outcome: Can produce complex and unique surface effects.
  1. Allows for creative and unique finishes.
  2. Can produce depth and texture on the ceramic surface.
  1. Requires extensive testing to achieve desired results.
  2. Risk of unexpected interactions between different glaze layers.

Glaze Testing


Glaze testing is the practice of applying glazes to test tiles and firing them to evaluate the results.


  • Methodology: Involves applying glaze to small ceramic pieces and firing them.
  • Purpose: To predict how the glaze will behave on a larger, final piece.
  1. Provides valuable insights into glaze behavior.
  2. Helps in fine-tuning glaze recipes and firing schedules.
  1. Consumes time and resources.
  2. Results may vary when scaling up to larger pieces.

Analogies for Understanding Glaze Structure

Understanding glaze structure through these analogies can provide valuable insights for both beginners and experienced potters. Hopefully my analogies are not too abstract. My analogies simplify the complexities involved, and offer a starting point for deeper exploration into the world of glazes.

Glaze Analogy ComponentRepresents
BreadSilica, the glass former
Peanut ButterFlux, lowers the melting point
JellyAlumina, adds stiffness

Glaze Structure Analogy: Bread, Peanut Butter, and Jelly

Sounds yummy already, right! In this analogy I use it to simplify the complex chemistry of glaze structure into more relatable terms.

  • Bread represents Silica, the glass former.
  • Peanut Butter represents Flux, which lowers the melting point.
  • Jelly represents Alumina, which adds stiffness to the molten glaze.

Glaze Components Analogy: The Building Blocks

The components of a glaze are likened to building blocks in a structure:

  • Foundation Blocks represent Silica, providing the base structure.
  • Mortar represents Flux, binding the blocks together.
  • Support Beams represent Alumina, providing additional strength.

Glaze Components Analogy: The Orchestra Analogy

The components of a glaze are likened to instruments in an orchestra:

  • Violins represent Silica, setting the tone.
  • Drums represent Flux, providing the rhythm and pace.
  • Cellos represent Alumina, adding depth and complexity.

I hope this article helps you understand the important terms and concepts related to pottery glazes!

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