How do underglaze, in-glaze, and on-glaze ceramic decorating techniques differ?

by Chanicha T

For those starting out in ceramics or looking for ceramic decorating techniques, you may have heard terms like Underglaze, In-glaze, and On-glaze (Overglaze), but are unsure how each technique differs and which type of work it is suitable for.

All three techniques use "color" to decorate ceramic pieces, but it's crucial for ceramic artists to understand the timing of color application, the position of the color after firing, and the resulting surface texture. These factors all impact the beauty, durability, and practical use of the finished piece.

Today, Pottery Clay will introduce you to Underglaze, In-glaze, and On-glaze, and help you choose the right technique for your work.

1. Underglaze

Underglaze is a decorating technique where color is applied to the piece before clear glazing. After glaze firing, the color remains beneath the glaze layer, protecting the design and making it highly durable.

Working Steps

Form and decorate the piece → Bisque Firing → Apply Underglaze → Apply clear glaze → Glaze Firing

Highlights of Underglaze

  • Excellent durability against wear and scratches when properly glazed and fired.

  • Ideal for creating patterns, details, and paintings on ceramic pieces.

  • Allows for varying color intensity (light-dark) and detailed work, similar to painting.

  • Suitable for work where designs are desired beneath a clear glaze layer.

  • A popular technique for contemporary ceramics and studio decoration work.

Note: If the piece is intended for food or drink, it is important to select colors and glazes that the manufacturer specifies as food-safe and to fire them at the recommended temperatures to ensure the finished piece is safe and suitable for practical use.

2. In-glaze

In-glaze is a decorating technique where colors or colorants react with the glaze layer during the firing process. The colors fuse and become an integral part of the glaze, creating unique, dimensional, and deep color effects.

This technique requires an understanding of glazes, firing temperatures, and kiln control, making it suitable for experienced ceramic artists who want to experiment with more complex decorating techniques.

Highlights of In-glaze

  • Colors and glaze fuse together during firing, creating unique effects.

  • Provides a soft, deep color dimension within the glaze layer.

  • Can create surface effects and color shades different from regular coloring.

  • Often found in specialized ceramic work, including porcelain and some types of industrial production.

Note: Artists need to properly control the temperature and atmosphere within the kiln, and choose colors and glazes that are compatible. The color results may vary depending on the glaze formula, temperature, and firing atmosphere.

3. On-glaze or Overglaze

On-glaze or Overglaze is a technique for decorating a piece after it has been glazed and glaze-fired. Color, decals, or special decorative materials are then applied to the glazed surface before the piece is refired at a lower temperature to adhere the color or material to the surface.

This technique is suitable for work requiring bright colors, intricate details, and special decoration, such as gold, silver, or luster application to create shimmer and unique effects.

Working Steps

Glaze firing completed → Apply On-glaze / Decorate with Decal / Apply gold → Refire at low temperature

Highlights of On-glaze or Overglaze

  • Provides bright and vivid colors, suitable for prominent designs.

  • Can capture fine lines and small details well.

  • Supports special decorating techniques such as gold, silver, and luster application.

  • Suitable for decorative ceramics, art pieces, and work requiring high precision.

Note: Since colors and decorative materials are on the uppermost layer of the glaze, their resistance to abrasion and chemicals may be less than decorations that are beneath or integrated into the glaze layer. Therefore, it is important to consider the intended use of the piece.

On-glaze techniques are thus suitable for display pieces, artwork, and decorative items, or pieces that are not frequently washed or scrubbed. For functional pieces, it is advisable to check the manufacturer's recommendations for each type of color and decorative material before use.

Therefore, when choosing a ceramic decorating technique, consider the characteristics of the piece, the desired outcome, durability, and intended use. If you want to draw patterns and details on the piece, Underglaze is a flexible and popular choice. If you want dimensional color effects and specialized techniques, In-glaze might be more suitable. For those who love bright colors, intricate details, or decoration with gold, silver, and luster, On-glaze or Overglaze is another interesting technique.

Regardless of the technique chosen, understanding ceramic colors, glazes, and firing temperatures will help you better control the outcome of your pieces and create beautiful ceramic works exactly as desired.

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