---
title: Clay in a terrarium | Glass Jar Garden
description: Clay: Heavy, sticky soil that holds water hard. Use a little at most. In the jar it has holds water 45 % by volume, pore space 50 % by volume, weight 950 g/L.
url: https://glassjar.garden/guide/soils/clay/
---

Soils and layers

# Clay

Heavy, sticky soil that holds water hard. Use a little at most.

## What the simulation uses

- Holds water: 45 % by volume (Water it keeps after draining; the rest runs down to the drainage.)

- Pore space: 50 % by volume (Room for air and water between grains; low means roots suffocate when wet.)

- Weight: 950 g/L (How heavy a litre is.)

- pH: 5 to 8 pH (How acid it keeps the soil.)

- Mould risk: low (How much fresh food it gives white mould; high-risk soils fuzz over in the first weeks.)

- Nutrients: medium (Plant food it brings.)

- Presses down to: 72 % of its loose depth (How far pressing can pack it, keeping its weight.)

## Description
These ultra-fine particles turn sticky when wet and cling to water and nutrients, leaving almost no room for air. A deep layer waterlogs and rots roots. Keep it to backgrounds or a small share of a mix.

Also called modelling clay substrate, clay soil.

Estimated, where sources were thin: mineral-specific CEC (kaolinite ~3-15 vs smectite 80-150) not on fetched page; AFP estimated.

## Sources

- [en.wikipedia.org/wiki/Clay](https://en.wikipedia.org/wiki/Clay)
- [engineeringtoolbox.com/density-solids-d_1265.html](https://www.engineeringtoolbox.com/density-solids-d_1265.html)
- [engineeringtoolbox.com/density-materials-d_1652.html](https://www.engineeringtoolbox.com/density-materials-d_1652.html)
- [en.wikipedia.org/wiki/Cation-exchange_capacity](https://en.wikipedia.org/wiki/Cation-exchange_capacity)

[Grow it in a jar](https://glassjar.garden/?guide=soils/clay)

[Calcined clay](https://glassjar.garden/guide/soils/calcined-clay/) · [Coco coir](https://glassjar.garden/guide/soils/coco-coir/) · [All soils and layers](https://glassjar.garden/guide/soils/)