# How to Score and Slip Correctly

Unit: Handbuilding Basics
Topic: Scoring & Slipping
URL: https://claybook.studio/learn/how-to-score-and-slip-correctly/

# The Technique Step by Step

Knowing *why* we score and slip is important. Knowing exactly *how* to do it is what keeps your work together.

## Step-by-Step

1.  **Identify both surfaces** that will meet.
2.  **Score surface A**: Scratch a firm crosshatch pattern, about 1cm square.
3.  **Score surface B**: Do the same on the matching surface.
4.  **Apply slip to surface A**: Use a brush, your finger, or a small tool. You want a visible coat: not a flood, not a thin smear.
5.  **Press together firmly**: Push the two pieces together with real pressure. Wiggle slightly to help the slip spread and the two surfaces mesh.
6.  **Blend the seam**: Use a finger or wooden tool to blend clay from one piece into the other on any accessible side.

## The Moisture Match Rule

The two pieces you are joining should be at roughly the **same moisture level**. Joining very wet clay to leather hard clay is risky. The wet piece will shrink more than the leather hard piece, cracking the join as they dry.

**The Fix**: If moisture levels do not match, wrap the drier piece in a damp cloth for 15 minutes before joining.

## Common Mistakes

*   **Dry slip**: If your slip has dried on the surface before you press, it acts as a barrier, not a bond. Apply slip just before joining.
*   **Not enough pressure**: A gentle press is not enough. Press firmly and wiggle.
*   **Skipping one surface**: Both surfaces need to be scored. One is never enough.

## Premium Repair Strategy

If a join looks weak before bone dry:

*   Re-open the seam carefully.
*   Re-score both surfaces.
*   Add fresh slip and re-press with firm pressure.
*   Add a thin reinforcing coil and blend well.

Early repair is far easier than post-firing regret.

## Pro Tip

After joining, run a thin coil of soft clay along the seam and blend it in. This is the single best thing you can do to guarantee a strong join, especially on the inside.

## Keep Exploring

The moisture-matching rule exists because [clay minerals](https://en.wikipedia.org/wiki/Clay_minerals) shrink as water leaves the spaces between their plate-like layers. When two pieces at different moisture levels are joined, they shrink at different rates and the resulting stress fractures the bond. This is the same principle behind [differential shrinkage](https://en.wikipedia.org/wiki/Thermal_expansion) cracking in engineering materials.

## Check your understanding

### Question 1: What is wrong with joining very wet clay to leather hard clay?

- [ ] A. The colours will not match
- [x] B. Different shrinkage rates will crack the join
- [ ] C. The slip will not stick
- [ ] D. Nothing, it is fine

Tip: They shrink at different rates as they dry. The wetter piece shrinks more, cracking the join.

### Question 2: What should you do after pressing two scored and slipped surfaces together?

- [ ] A. Leave it to dry immediately
- [x] B. Blend the seam with a finger or tool
- [ ] C. Apply glaze to seal it
- [ ] D. Fire it straight away

Tip: Blend clay from one piece into the other along the seam with a finger or tool to reinforce the join.

### Question 3: What happens if the slip on the surface has already dried before you press the pieces together?

- [ ] A. The join is stronger because it is dry
- [x] B. Dry slip acts as a barrier, weakening the join
- [ ] C. Nothing, dried slip is fine
- [ ] D. The pieces will not stick at all and slide apart

Tip: Dry slip acts as a barrier, not a bond. It prevents the two surfaces from truly fusing together.