The key to successfully applying wet clay to dry clay is to ensure the moisture levels are as even as possible between the two pieces before joining them. This prevents cracking and separation during the drying and firing process.
Understanding the Problem
Uneven moisture content is the primary reason for failure when joining clay pieces. When wet clay is applied to dry clay, the dry clay sucks the moisture out of the wet clay very quickly. This rapid drying can lead to:
- Cracking: The wet clay shrinks as it dries, and the dry clay provides resistance.
- Separation: The bond between the two clay bodies weakens or breaks completely.
The Solution: Equalizing Moisture
The goal is to get both pieces of clay to a similar moisture level before attaching them. Here's a breakdown of how to achieve this:
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Re-wet the Drier Piece:
- Score and Slip: Score both surfaces (make cross-hatched lines) where they will be joined. Apply slip (a creamy mixture of clay and water) generously to both scored areas. The slip acts as a glue and helps to reintroduce moisture to the drier piece.
- Damp Sponge/Cloth: Lightly dampen the dry clay with a sponge or cloth. Be careful not to oversaturate it; you just want to increase the moisture level slightly. Repeat this several times, allowing the moisture to absorb between applications.
- Wrap in Damp Paper Towels (for larger pieces): For larger dry clay pieces, wrapping them in damp paper towels covered by plastic can gradually reintroduce moisture without making the clay too soft.
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Dry Out the Wetter Piece (if necessary):
- Air Drying: Allow the wet clay to air dry slightly before attaching it.
- Fan: Use a fan to gently speed up the drying process.
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Joining the Pieces:
- Apply Firm Pressure: Once the moisture levels are closer, firmly press the pieces together.
- Blend the Seam: Use tools to blend the wet clay into the dry clay, smoothing the seam.
- Add Coils (optional): For a stronger bond, consider adding small coils of clay along the seam and blending them in.
Important Considerations
- Clay Body: Using the same clay body for both pieces is ideal, as they will have similar shrinkage rates.
- Drying Time: Dry the joined piece slowly and evenly to prevent stress and cracking. Consider covering it loosely with plastic to control the drying rate.
- Experience: Practice makes perfect. Don't be discouraged if your first attempts aren't perfect.
By focusing on equalizing the moisture content, you can significantly improve your success rate when joining wet and dry clay.
