Introduction to Modelling IV - Processes of drying and firing clay works - Finishing techniques

Introduction

In modelling, the journey from a wet clay sculpture to a finished piece of art involves careful preservation and chemical transformation. This stage is crucial because improper drying or firing can lead to the destruction of the work through cracking or exploding. This lesson focuses on how to transition clay from its plastic state to a durable, finished ceramic form.

Key Points

1. Drying Processes

Before clay can be fired, all physical water must evaporate. This happens in two main stages:

• Leather-hard Stage: The clay is stiff enough to be handled without deforming but still contains enough moisture to be carved or joined.
• Bone-dry (Greenware): The clay is completely dry, feels room temperature, and is very fragile. It is now ready for the kiln.
• Precaution: Clay must be dried slowly away from direct sunlight to prevent warping and cracking.

2. Firing Processes

Firing is the process of heating clay to high temperatures in a special oven called a Kiln.

• Bisque Firing: This is the first firing. It transforms the fragile bone-dry clay into a hard, porous state called "Bisque." Once fired, the clay can no longer be turned back into mud.
• Kiln Types: These can be traditional (open pit firing) or modern (electric or gas kilns).

3. Finishing Techniques

Once the work is fired, various techniques are used to enhance its appearance and durability:

• Burnishing: Rubbing the surface of the leather-hard clay with a smooth stone or spoon to create a shiny, polished effect before firing.
• Glazing: Applying a liquid coating of minerals (glaze) and firing it again. This creates a glass-like, waterproof, and colorful finish.
• Painting: Applying cold colors like acrylics or poster colors to the fired bisque ware (usually for decorative pieces that won't hold water).
• Incising: Cutting or carving patterns into the surface of the clay during the leather-hard stage.

Brief Summary

The transformation of clay into a permanent ceramic work requires patient drying to the bone-dry stage, followed by bisque firing in a kiln to harden the material. Finally, finishing techniques like glazing or burnishing are applied to give the work its final aesthetic and functional value.