# Setting the Floor: Thickness and Compression

Unit: Conquering the Wheel
Topic: Opening the Center
URL: https://claybook.studio/learn/setting-the-floor-thickness-and-compression/

# The Foundation of Your Pot

The floor of a pot is its most structurally important part. Get it right now, and everything becomes easier. Get it wrong, and no amount of skill in pulling can save the pot.

## How Thick Should the Floor Be?

A common guideline: the floor should be approximately as thick as the walls you intend to throw. For most beginners, that means roughly 8–10mm (about 3/8 of an inch).

*   Too thin: the pot is fragile, may crack, and will distort when trimmed.
*   Too thick: the pot is heavy and clunky, and it will take forever to dry.

## Checking Floor Thickness

Use a **needle tool**. While the wheel is spinning:

1.  Hold the needle tool vertically.
2.  Slowly push it straight down through the floor until it just touches the bat or wheel head.
3.  Pinch the needle with your fingers at the clay surface level.
4.  Pull it out and measure the length of needle below your fingers. That is your floor thickness.

## Compressing the Floor

After opening, you must compress the floor. Use the flat pad of your middle or index finger to press firmly in slow concentric circles from the center outward across the floor.

Compression does two critical things:

*   **Strengthens the clay**: Aligned particles resist cracking better.
*   **Prevents the floor from cracking** as it dries. An uncompressed floor often cracks right through the center during drying.

## Pro Tip

A floor that is compressed well has a slightly smoother, denser look than the surrounding clay. You can often see the difference.

## Floor Safety Checklist
Before first pull:
* Needle-check floor thickness
* Compress floor in slow circles
* Remove pooled water from center

A stable floor makes every later step easier.

## Dig Deeper

Opening the clay on a [potter's wheel](https://en.wikipedia.org/wiki/Potter%27s_wheel) transforms a solid centered mound into the beginning of a hollow vessel. Compressing the floor works because of [compression](https://en.wikipedia.org/wiki/Compression_%28physics%29) at the particle level, where balanced inward forces align and strengthen the clay body, helping it resist cracking as it dries.

## Check your understanding

### Question 1: How do you measure floor thickness while throwing?

- [ ] A. Guess by eye from above
- [x] B. Use a needle tool pushed down to the bat
- [ ] C. Feel it from the outside
- [ ] D. Measure after removing the pot

Tip: Push a needle tool straight down through the floor until it hits the bat, then pinch it at the clay surface and measure the length below your fingers.

### Question 2: Why is compressing the floor so important?

- [ ] A. It makes the floor look shiny
- [x] B. It strengthens clay and prevents cracking during drying
- [ ] C. It removes water from the clay
- [ ] D. It helps the pot release from the bat

Tip: Compression aligns the clay particles, strengthening them and preventing the floor from cracking as the pot dries.