For those new to ceramics, the terms Bisque or Biscuit Firing are sure to come up during the working process. However, many may still be confused as to whether Bisque is a type of clay.
The answer is Bisque is not a type of clay, but refers to a ceramic piece that has undergone its first firing.
Bisque firing is a crucial step that transforms a dried clay piece into a strengthened form, ready for decoration, glazing, and the final firing.
What is Bisque?
Before becoming Bisque, the piece must go through various stages, from clay preparation and shaping to complete drying.
The typical workflow is: Clay → Shaping → Greenware → Bone Dry → Bisque → Glazing → Glaze Firing → Finished Ceramic
Once the piece is completely dry or in a Bone Dry state, it can be loaded into the kiln for the first firing.
During firing, residual water in the clay body is eliminated, and certain components in the clay undergo physical and chemical changes, making the piece stronger but still porous.
This porosity is important because it allows glaze to penetrate the surface of the piece.
Therefore, Bisque is a stage that bridges clay forming and glazing.
What types of clay can be bisqued?
Since Bisque is the result of the first firing, not a type of clay, it can be achieved with many types of clay bodies.
Common clays include Earthenware, Stoneware, Porcelain
However, each type of clay has different compositions and properties, leading to different firing temperatures and water absorption rates.
1. Earthenware Clay
Earthenware is a low-temperature firing clay, commonly used for pottery, decorative items, and works that benefit from the color of the clay body and glaze.
Earthenware clay bodies can come in various colors, from white, cream, and yellow to red and brown, depending on the specific blend.
After firing, this type of clay typically remains quite porous.
Highlights of Earthenware
- Easy to shape
- Suitable for beginners
- Ideal for hand-building
- Variety of clay body colors
- Compatible with low-fire glazes
- Suitable for decorative and sculptural work
Earthenware is therefore a good choice for beginners in ceramics or those looking to create colorful and uniquely textured pieces.
2. Stoneware Clay
Stoneware is a very popular clay body for making functional ware and general ceramics.
When fired to the appropriate temperature, the clay body undergoes more vitrification, resulting in a denser, stronger body with less water absorption compared to Earthenware.
Stoneware can be used for both wheel throwing and hand-building.
Highlights of Stoneware
- Strong
- Suitable for functional ware
- Ideal for wheel throwing
- Ideal for hand-building
- Variety of clay body colors
- Accommodates various types of glazes
Stoneware is thus one of the ideal clay bodies for ceramic artists looking to progress from experimental pieces to functional ware.
3. Porcelain Clay
Porcelain is a fine-grained clay with kaolin as a key component. Its distinguishing features are its white color, fine texture, and ability to create thin and delicate pieces.
When fired to the appropriate temperature, porcelain can achieve a dense body, and in thin pieces, it may exhibit translucency.
Highlights of Porcelain
- Fine-grained clay body
- Clean white color
- Suitable for high-detail work
- Ideal for fine ceramics
- Suitable for thin pieces
- Can create highly refined works
However, porcelain requires more skill in shaping and drying control than some other clay bodies, as pieces can warp or crack if moisture is not carefully managed.
Is Bisque the same for all types of clay?
Not entirely.
Although Earthenware, Stoneware, and Porcelain can all be bisqued, what needs to be considered is the temperature range specified by the manufacturer for that particular clay body.
It's important to note that Bisque does not mean the clay is fully mature or vitrified.
For example, Stoneware with a typical firing range of Cone 5–6 might be bisqued at a lower temperature. It is then glazed and fired again to the appropriate temperature for the specific clay body.
Therefore,
Bisque Firing = First firing
Glaze Firing = Final firing to mature the clay and glaze
Why bisque fire before glazing?
Bisque firing offers several benefits:
1. Makes the piece stronger
Dried clay or greenware is still fragile and easily broken. Bisque firing strengthens the piece, making it easier to handle for decoration.
2. Keeps the piece porous
The porosity of bisqued ware helps absorb water from the glaze, allowing the glaze to adhere to the surface of the piece.
3. Reduces the fragility of greenware
After bisquing, the piece can be underglazed or glazed without the same level of caution as with greenware.
4. Prepares the piece for the final firing
Once glazed, the piece proceeds to Glaze Firing, a stage where the clay body and glaze develop according to the specified temperature.
What is Bisque suitable for?
After bisque firing, pieces can be further worked on in various ways, such as:
- Glazing: This is the primary use of bisqued ware, where the porous surface helps absorb water from the glaze.
- Underglazing: Used for drawing patterns, painting, or creating details before applying a clear glaze.
- Surface Decoration: Various decorative techniques can be applied to bisqued ware.
- Sculpture: In some cases, bisqued ware can serve as the final state for sculptures or decorative pieces that do not require glazing.