---
title: "Does alumina float in water? No"
description: "Alumina sinks — its density is 3,900 kg/m³ against water's 1,000. Why density and not weight decides it."
url: https://atoneplace.net/does-it-float/alumina/
site: "At One Place"
---

# Does alumina float?

**Does alumina float?: No**

3,900 kg/m³ against water's 1,000

Alumina sinks. At 3,900 kg/m³ it is 3.90 times denser than water.

## Why

Floating is decided by density alone — mass divided by volume — compared against the fluid. Weight has nothing to do with it directly: a 200-tonne ship floats and a 2-gram pebble sinks, because the ship encloses enough air to bring its average density below that of water. That is also the only reason a steel hull works.

## The numbers

- **Density:** 3,900 kg/m³ (3,700–3,980)
- **Relative to fresh water:** 3.900×
- **Floats in fresh water:** No
- **Floats in seawater:** No

## Compared with other materials

| Material | Density | Floats |
| --- | --- | --- |
| asphalt (hot-mix) | 2,350 kg/m³ | No |
| concrete | 2,400 kg/m³ | No |
| porcelain | 2,400 kg/m³ | No |
| limestone | 2,450 kg/m³ | No |
| reinforced concrete | 2,500 kg/m³ | No |
| soda-lime glass | 2,500 kg/m³ | No |
| tempered glass | 2,500 kg/m³ | No |
| quartz | 2,650 kg/m³ | No |
| aluminum | 2,700 kg/m³ | No |
| aluminum 6061 | 2,700 kg/m³ | No |

## Common questions

### Does alumina float in water?

No — at 3,900 kg/m³ it is denser than water's 1,000.

### Does weight decide whether something floats?

No, density does. A 200-tonne ship floats and a small pebble sinks, because the ship encloses enough air to bring its average density below water.

## Related pages

- [Alumina properties](https://atoneplace.net/material/alumina/)
- [Does air float?](https://atoneplace.net/does-it-float/air/)
- [Does expanded polystyrene foam float?](https://atoneplace.net/does-it-float/eps-foam/)
- [Does rigid polyurethane foam float?](https://atoneplace.net/does-it-float/polyurethane-foam/)
- [Does EVA foam float?](https://atoneplace.net/does-it-float/eva-foam/)
- [Does balsa float?](https://atoneplace.net/does-it-float/balsa/)
- [Does corrugated cardboard float?](https://atoneplace.net/does-it-float/cardboard/)
- [Does cork float?](https://atoneplace.net/does-it-float/cork/)
- [Does western red cedar float?](https://atoneplace.net/does-it-float/cedar/)

## Sources

- Typical range compiled from manufacturer specifications — At One Place (/about/)