---
title: "What Are Beer Bubbles? Home Experiments to Explain How They Form"
description: "Bubbles are small packets of carbon dioxide (CO2) seeking to escape the liquid, pushed upward by the buoyancy force described by Archimedes."
url: https://www.thebeertimes.com/en/what-are-beer-bubbles-physics-home-experiments/
date: 2024-09-18
modified: 2026-06-28
author: "Carlos Uhart M."
image: https://www.thebeertimes.com/wp-content/uploads/2017/04/Burbujas_en_la_cerveza.jpg
categories: ["Culture"]
tags: ["Culture", "Science"]
type: post
lang: en
---

# What Are Beer Bubbles? Home Experiments to Explain How They Form

By **[Jorge Díaz](https://conexioncausal.wordpress.com/2017/04/10/burbujas-en-la-cerveza-y-algo-de-fisica/)**

It’s been almost a year since I stopped working in physics professionally; however, one thing that’s impossible to leave behind is looking at the world through the eyes of physics.

![Beer bubble](https://www.thebeertimes.com/wp-content/uploads/2017/04/Burbujas_en_la_cerveza.jpg)*Beer bubbles and a bit of physics*

Just as ducks swimming make me think of electrons moving faster than light in water, another thing that puts a smile on my face every time I see it is the continuous flow of bubbles in a beer.

## What are beer bubbles?

Bubbles are small packets of carbon dioxide (CO2) seeking to escape the liquid, pushed upward by the [buoyancy force described by Archimedes](https://en.wikipedia.org/wiki/Archimedes%27_principle) — the one that, according to legend, made him shout “Eureka!”

The size of bubbles changes as they rise; though not so easy to notice, they grow larger as they approach the surface.

![CO2 molecule](https://www.thebeertimes.com/wp-content/uploads/2016/12/Molecula_co2.jpg)

If curiosity is stronger than thirst, it’s enough to observe carefully to notice that bubbles originate near the glass wall. This happens because micro-bubbles of CO2 cluster at what are called “nucleation sites” — [microscopic irregularities in the glass](https://www.thebeertimes.com/cristaleria-de-cerveza-nucleada-todo-lo-que-necesitas-saber/) where gas accumulates until it is released as a bubble.

CO2 bubbles form at tiny imperfections in the glass in the same way that raindrops form around dust particles, or tracks in a bubble chamber are formed by the passage of a charged particle.

In fact, its inventor tested the idea behind its creation by exposing beer to radioactive materials.

Something fairly obvious is that bubble speed increases as they rise — that is, they accelerate. Before continuing, I’d like to clarify the definition of these concepts.

## Bubble velocity

This refers to the change in position Δx over time Δt. If an object does not move (its position stays constant over time), we say it has zero velocity; conversely, if its position changes, we say it has a certain velocity.

If we call Δx the change in position and Δt the elapsed time, then velocity is mathematically defined as:

v = rac{\Delta x}{\Delta t}

## Bubble acceleration

This refers to the change in velocity Δv over time Δt. If an object always moves at the same velocity, we say it has zero acceleration; conversely, if its velocity changes, we say it has a certain acceleration.

If we call Δv the change in velocity and Δt the elapsed time, then acceleration is mathematically defined as:

a = rac{\Delta v}{\Delta t}

This is where the beauty of physics, algebra and geometry come together to give us a complete description of accelerated motion.

For simplicity, let’s assume a bubble has constant acceleration — that is, it does not change over time (this turns out not to be entirely true, but it is a good approximation).

## Bubble position

Unlike acceleration, the position of each bubble changes (they move upward) and their velocity changes at a constant rate (they move faster and faster).

On a graph this would look like the left image, where velocity (vertical axis) increases from an initial value of zero to a final value v after a certain time t.

![Velocity vs. time curves](https://www.thebeertimes.com/wp-content/uploads/2017/04/v2.jpg)*Velocity vs. time*

The right-hand figure shows the same graph with more detail, where it has been assumed that measurement begins at t=0; therefore Δt = t.

Then, a bit of basic algebra allows us to rewrite the final velocity using the definition of acceleration.

Physics tells us that on a velocity vs. time graph, the distance traveled is given by the area under the curve; and geometry allows us to calculate the area of a triangle with base = t and height = at.

From this we obtain that the motion of a bubble (its height measured from the nucleation center) is:

x = rac{1}{2} a t^2

This is where we can put physics to the test: all we need to do is photograph one of those bubble streams and measure their displacement.

## Bubble displacement

Some time ago I couldn’t resist observing how bubbles rose [in a beer glass](https://www.thebeertimes.com/vasos-y-copas-imprescindibles-para-cualquier-amante-de-la-cerveza/).

A few days later there was a celebration at the company where I work, and before joining my colleagues to enjoy a glass of Prosecco, I took the time to capture the bubbles. Later I repeated the experiment with a glass of sparkling water.

![Bubbles in a glass of Prosecco and a glass of water](https://www.thebeertimes.com/wp-content/uploads/2017/04/burbujas_agua_.png)*Prosecco vs. water*

I then used a simple image editor to record the position of each bubble. In the absence of a unit of measurement, I simply used pixels.

I didn’t have time data either; however, each bubble is released when nucleation reaches a threshold at which the buoyancy force frees it, so it is natural to assume the same time elapses between one bubble and the next.

![Displacement vs. bubbles curves](https://www.thebeertimes.com/wp-content/uploads/2017/04/quadratic_fits.png)*Displacement vs. bubbles*

I plotted the displacement of each bubble in pixels on the vertical axis and assigned consecutive numbers to each bubble for the horizontal axis.

The data are shown in the figure by the blue dots, and the red line indicates the quadratic fit to the data in each case.

In particular, the beer bubbles show that a quadratic function (that is, position varies as the square of time) fits the data very well.

## Conclusions

Obviously, I’m not the first to turn a refreshing drink into a physics laboratory. However, it should be noted that for simplicity I have only considered the buoyancy force acting on each bubble.

There are other factors that affect their motion — for example, the drag force due to their size, which increases continuously.

These details, especially the growth of each bubble, require concepts that go beyond the scope of this post.

For those who are interested, the article “[Through a Beer Glass Darkly](https://web.stanford.edu/group/Zarelab/publinks/421.pdf),” Physics Today 44 (1991), covers the details; it only requires basic knowledge of calculus and gas theory.

There are also various studies on the downward motion of bubbles in Guinness beer, such as “[Why do bubbles in Guinness sink?](https://staff.ul.ie/eugenebenilov/hpage/pubs/ajp13.pdf)” Am. J. Phys. 81, 2 (2013).

## Frequently Asked Questions (FAQ)

### 1. Why do bubbles in nitrogenated beers appear to fall rather than rise?

Unlike traditional beers, these beers use nitrogen instead of CO2 alone. Nitrogen bubbles are smaller and, due to a circular convection effect in the glass, the liquid in the center rises rapidly carrying bubbles upward, while the liquid near the glass walls descends, pulling peripheral bubbles downward — creating the optical illusion that they are “falling.”

### 2. What is the difference between beer bubbles and those in champagne or sparkling wine?

The main difference lies in gas concentration and proteins. Beer contains proteins that stabilize bubbles, allowing them to form a persistent foam head. In champagne (or Prosecco), without these proteins, bubbles burst quickly upon reaching the surface, releasing aromatic compounds more volatilely, but without creating a stable head.

### 3. How does temperature affect bubble speed and size?

According to Henry’s law, the solubility of a gas decreases as temperature rises. In a warm beer, CO2 is released much more aggressively and uncontrollably, generating larger bubbles and faster gas loss. A low temperature (between 4 and 7°C) allows the gas to be released gradually, maintaining effervescence for longer.

### 4. Why is the glass essential for bubble formation?

The process is called nucleation. Bubbles need a support point to form; if a glass were perfectly smooth at the microscopic level, the beer would barely have any bubbles. Many manufacturers laser-etch small dots into the bottom of the glass (nucleation points) to ensure a constant and aesthetically pleasing flow of bubbles to the surface.

### 5. Is it true that dust or dirt on the glass affects effervescence?

Yes. Dust particles or detergent residue act as artificial nucleation centers. If you see bubbles erupting chaotically from the sides of the glass rather than following a clean vertical flow, the glass likely has impurities. A “beer-clean” glass ensures that nucleation occurs primarily at the points designed for it.

## Recommended

- [Pilsner Urquell, the history of the original “blonde” beer](https://www.thebeertimes.com/en/pilsner-urquell-plzensky-prazdroj-the-origin-of-the-first-blonde-beer-in-history/)
- [How to avoid a hangover and how to cure it: what you need to know](https://www.thebeertimes.com/que-es-y-como-se-puede-evitar-la-resaca/)