Frit is a pre-melted glass material created by melting various minerals or chemicals, such as silica, flux, and other compounds, at high temperatures. This molten material is then rapidly cooled and ground into a fine powder for use as an ingredient in ceramic glazes.
This melting process helps stabilize certain raw materials that might otherwise be water-soluble or toxic in their original form. It reduces the dissolution of certain substances and helps ensure consistent quality in glaze production.
Currently, frit is an essential raw material used in the ceramic industry worldwide, in both art and industrial production.
What is the function of frit in ceramics?
Frit plays a crucial role in the development of ceramic glazes by:
- Stabilizing glaze formulas.
- Reducing the water solubility of certain raw materials.
- Helping the glaze melt at the desired temperature.
- Controlling the gloss, matte, and surface texture of the glaze.
- Increasing the consistency of color and glaze surface.
- Helping develop lead-free glazes.
At what firing temperatures is frit used?
Frit can be used for both low and high-temperature glazes, depending on the type of frit and the glaze formula.
Generally:
- Low Fire Glaze: Approximately Cone 06–04 (999–1060°C)
- Overglaze Decoration: Approximately 650–800°C
- Mid-High Fire Glaze: Approximately Cone 5–10 (1,180–1,305°C)
Each manufacturer specifies the appropriate temperature range for different types of frit.
Types of frit used in the ceramic industry
Frit can be classified into several types based on its chemical composition. Common types include:
1. Lead Frit
This frit provides high gloss and melts easily. However, due to its lead content, its use has significantly decreased, especially for food contact ware.
2. Lead Borate Frit
It melts well, providing a smooth and glossy glaze surface. However, it has safety limitations similar to lead frit.
3. Borosilicate Frit
This is the most popular type of frit used today.
Key features include:
- Lead-Free
- Produces clear glazes
- High chemical durability
- Suitable for tableware and general ceramic applications
This type of frit is the basis for many widely used clear glaze formulas.
4. Opacifying Frit
This type of frit contains opacifiers such as Zirconium Silicate or Tin Oxide to give the glaze an opaque or semi-opaque white appearance. It is suitable for white and pastel-colored glazes.
Note: Opacity is not solely due to "borosilicate frit" but depends on the glaze formula and the added opacifier.
Lead-Free Frit
Currently, most ceramic raw material manufacturers choose Lead-Free Frit to ensure glazes are safer, especially for food and beverage ware and everyday items.
However, the safety of tableware does not depend solely on the frit, but also on the glaze formula, correct firing, and standard testing for heavy metal leaching.
Choosing the right frit for your glaze formula
Several factors should be considered when selecting frit, such as:
- Firing temperature
- Type of clay body
- Gloss or matte finish of the glaze
- Glaze color
- Coefficient of Expansion
- Compatibility with the glaze formula
Choosing the appropriate frit helps reduce problems like crazing, shivering, and improves the quality of the glaze surface.
Pottery Clay offers advice on ceramic raw materials
Pottery Clay sells a complete range of ceramic raw materials and equipment. We provide advice on selecting frit, glazes, and various raw materials suitable for production, for beginners, students, artists, and ceramic factories.
If you need to develop glaze formulas or choose raw materials suitable for your firing temperature, the Pottery Clay team is ready to consult with you.