---
title: Humidity and the lid: how the terrarium simulator works
description: Sealed jars keep every drop; open jars lose water to the room. Sealed: water goes round, out of leaves, onto the glass, back to the soil. Sealed air sits...
url: https://glassjar.garden/guide/how-it-works/humidity-and-the-lid/
---

How it works

# Humidity and the lid

Sealed jars keep every drop; open jars lose water to the room.

- Sealed: water goes round, out of leaves, onto the glass, back to the soil.
- Sealed air sits near 95 to 100% humidity.
- Open: water evaporates, faster when warm, dry or wide-mouthed.
- Venting lets some humidity and water out of a sealed jar.
- Glass fogs on cool mornings; fogged all day means too wet.

## Stats

- Open evaporation: 0.1 cm a day of wet surface at 20 °C

- Per °C warmer: 7% more

- Lid gasket leak: 0.02 air changes an hour

[See it in a jar](https://glassjar.garden/?guide=how-it-works/humidity-and-the-lid)

[← Water](https://glassjar.garden/guide/how-it-works/water/) · [Light →](https://glassjar.garden/guide/how-it-works/light/)