---
title: "Glaser makes a particle trail start the boiling"
description: "Why can a hot liquid remain clear, then grow bubbles along a particle’s path?"
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[Detecting a passing particle](https://sandboxphysics.com/stories/particle-evidence/#detectors)

Particles · Experiments · Discovery

# Glaser makes a particle trail start the boiling

Why can a hot liquid remain clear, then grow bubbles along a particle’s path?

Sandbox Physics · 2026-10-24

Nobel contribution: 1960-1

1. Prepare a pressurised liquid
2. Lower pressure into a sensitive state
3. Grow bubbles along deposited energy
4. Photograph and recompress

The liquid is both the material the particle crosses and the medium that records its passage.

## Hot enough to boil, yet still liquid

In 1952 at the University of Michigan, Donald Glaser showed that ionising radiation could trigger bubble formation in a superheated liquid. The liquid had been prepared so that it was hotter than its boiling temperature at the new pressure, yet had not begun boiling throughout its volume. A particle could disturb that waiting state locally. Tiny bubbles then grew along the places where it had deposited energy, making a visible track.

Boiling needs a beginning. A small bubble has a surface, and creating that surface costs energy. Very small bubbles tend to collapse unless conditions allow them to grow. A clean liquid can therefore remain in a temporary, unstable-seeming state even when vapour would be favoured overall. This is a metastable state: a disturbance can start a change that was not beginning everywhere on its own.

Glaser used a controlled pressure change to reach that condition. Under higher pressure the hot liquid remained liquid. Lower the pressure quickly and the boiling temperature falls, leaving the liquid superheated. The chamber becomes sensitive during the resulting interval. Enough local energy deposition can start bubbles large enough to survive and grow. Local energy deposition must meet the nucleation threshold, which depends on temperature, pressure and the properties of the liquid.

Sources: [1] [2]

## The bubbles grow after the particle has gone

The particle itself passes too quickly to follow with an ordinary camera. It leaves a set of microscopic disturbances. Bubbles grow from them for long enough to reach a photographable size, and a flash captures the track. The chamber is then recompressed. The bubbles disappear and the liquid can prepare for another cycle. The useful record is a frozen pattern from one carefully timed stage of a repeating thermodynamic process.

Timing matters because growth helps and then harms the image. Bubbles that are too small are difficult to see. Wait too long and neighbouring bubbles merge, obscuring the original line. Unwanted nucleation on the wall, dust or other disturbances can fill the view with bubbles unrelated to the particle. A practical chamber has to make the desired tracks clearly while controlling those other ways of starting a boil.

The familiar story that a glass of beer simply inspired the successful detector compresses the work too far. Glaser’s own lecture describes tests with warmed beer, ginger ale and soda water that showed no obvious gross difference when a radioactive source was nearby. The useful chamber came from a physical effect established with suitable superheated liquids, followed by the development of conditions in which charged-particle tracks could be photographed.

Sources: [2] [3]

## Liquid offers many targets in a small volume

A liquid contains far more atoms per unit volume than a gas under ordinary conditions. Particles are consequently more likely to interact in a chamber of manageable size. That helped make bubble chambers attractive for accelerator experiments: a beam could enter dense material, produce secondary particles, and leave visible paths through the same volume. Hydrogen was particularly useful because its nucleus is a single proton, simplifying the starting target in many reactions.

Using hydrogen required a separate engineering achievement. It had to be kept cold enough to be liquid, moved through the pressure cycle, and observed in a reliable chamber. Alvarez and colleagues developed large hydrogen chambers and the measurement systems needed to analyse their photographs. Glaser’s invention and those later advances belong to one line of instruments, with distinct contributions at each step.

Density is useful only if the event can still be interpreted. A heavier target nucleus has more constituents and may absorb or scatter outgoing particles before they leave it. Hydrogen offers a simpler initial proton for many studies. The chosen liquid therefore affects both the chance of making an interaction and the difficulty of explaining its products. It is part of the physics of the target as well as the engineering of the detector.

Sources: [4] [2]

## A curved line becomes a measurement

Place the chamber in a known magnetic field and track curvature adds information about momentum and charge. Photograph from several views and apparent crossings can be tested in three dimensions. Follow the tracks to a common point and they can reveal a collision or decay. A bubble chamber image is therefore the starting material for measurement, not the finished interpretation.

Glaser received the 1960 Nobel Prize for inventing the bubble chamber. His central idea joined a material on the verge of a phase change with a particle’s local energy deposition. The hot liquid supplied the amplification: a microscopic disturbance became a growing bubble, and a row of such disturbances became a path a human could inspect.

Sources: [2] [3]

Continue with the physics

## Try the related models

### [Bend a charged-particle beam](https://sandboxphysics.com/labs/charged-particle/)

Change the electric and magnetic fields and follow the trajectory.

The model follows a nonrelativistic particle through fixed, uniform fields.

## Sources and reading notes

1. [D. A. Glaser, Some effects of ionizing radiation on the formation of bubbles in liquids (1952)](https://doi.org/10.1103/PhysRev.87.665)

   The original report establishes the radiation-induced boiling effect that led to the bubble chamber.

2. [D. A. Glaser, Elementary particles and bubble chambers (1960)](https://www.nobelprize.org/uploads/2017/05/glaser-lecture.pdf)

   Glaser recounts superheated-liquid tests, early tracks and the requirements for a practical detector.

3. [CERN-EF-87-3, Bubble chambers (1987)](https://cds.cern.ch/record/177935/files/CERN-EF-87-3.pdf)

   The technical report describes nucleation, bubble growth, photography and recompression.

4. [L. W. Alvarez, Liquid hydrogen bubble chambers (1956)](https://www.osti.gov/biblio/915448)

   Alvarez reports the transition from small organic-liquid chambers to usable liquid-hydrogen chambers.

## Follow the next question

[Alvarez’s group finds short-lived particles in combinations of tracks](https://sandboxphysics.com/stories/particle-evidence/alvarez-resonance-events/)

[Wilson turns ionisation into a visible track](https://sandboxphysics.com/stories/particle-evidence/wilson-cloud-chamber/)

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