Gallium: The Metal That Melts in Your Hand

Melt a metal at body temperature, then watch a drop of it crumble aluminum foil into confetti
Beginner🕐30 min●Low hazardphysical-propertiesmetal

Summary

Gallium is a solid metal that turns to liquid at just under 30 °C — below body temperature. You’ll melt it with the warmth of your hand, cast it, and then use a single drop to embrittle aluminum, tearing a soda can apart like wet paper. Along the way you’ll meet melting points, the huge liquid range of gallium, and liquid-metal embrittlement — how one metal can destroy another by seeping into its grain boundaries.

History

Gallium was predicted by Mendeleev in 1871 as eka-aluminium, a missing element below aluminum, and found by Lecoq de Boisbaudran in 1875 — its properties matched the prediction so closely it became a famous confirmation of the periodic table. The aluminum-embrittlement effect is more than a parlor trick: it is a genuine engineering hazard, which is why gallium and gallium alloys are kept away from the aluminum airframes of aircraft.

Materials

  • A few grams of gallium metal (99.9 %+), in a plastic vial
  • A cup of warm water (~40 °C)
  • A silicone mold or small dish (never sealed glass — gallium expands when it freezes)
  • A strip of aluminum foil, or a clean empty aluminum drink can
  • Fine sandpaper or steel wool, and disposable gloves

Hazards & preparation

Note

Gallium itself is low-hazard — but it permanently destroys aluminum and stains other metals.

  • Take off aluminum and gold rings; keep gallium away from phones, cookware and jewelry.
  • Work on a disposable surface; use only scrap aluminum for the embrittlement step.
  • Wash hands afterward. Do not store gallium in sealed glass — freezing expansion can crack it.

See the Safety page.

Procedure

Part A — Melt and cast

  1. Stand the vial of gallium in a cup of warm water for a few minutes, or cup a lump in your bare palm.
  2. Watch it slump and pool into a bright, mirror-like liquid at 29.8 °C.
  3. Pour the liquid into a silicone mold and let it cool. It re-solidifies within minutes and can be re-melted endlessly.

Part B — Embrittle aluminum

  1. Lightly sand a patch of scrap aluminum foil or a can to break its oxide layer.
  2. Smear a drop of molten gallium onto the bare metal and leave it a few minutes to soak in.
  3. Gently flex the aluminum where the gallium sat — it now tears, crumbles, and flakes with almost no force.

What you should see

The solid metal collapses into a liquid at a temperature you can reach with a cup of tea, and re-freezes on cooling. In Part B, aluminum that was springy and tough before becomes shockingly brittle wherever the gallium reached — you can crumble it between your fingers.

Symptom Likely cause Fix
Gallium won’t melt Water not warm enough Use ~40 °C water; be patient
It won’t wet the aluminum Intact oxide layer Sand/scratch the aluminum first
Gallium beads up and rolls off skin Skin too cool / oily Warm your hand; it melts at ~30 °C

The Science

Gallium’s melting point is only 29.76 °C, yet it does not boil until 2400 °C — one of the widest liquid ranges of any element. The low melting point comes from its unusual crystal structure, in which atoms pair up rather than pack tightly.

In Part B, liquid gallium wets aluminum and diffuses along the grain boundaries — the interfaces between the tiny crystals that make up the metal. It weakens the bonds between grains, so the aluminum, though chemically unchanged, loses almost all of its mechanical strength. This is liquid-metal embrittlement, and it happens because the aluminum grains are now barely held to one another.

Questions to Explore

  1. Why does gallium melt in your hand but aluminum, just above it in the same group, needs 660 °C?

    Hint / answer

    Gallium forms an unusual crystal of paired atoms that is easy to pull apart, giving it an exceptionally low melting point despite being a metal. Aluminum packs into a dense, strongly bonded lattice.

  2. The gallium doesn’t dissolve the aluminum — so why does it fall apart?

    Hint / answer

    The gallium seeps along the boundaries between the aluminum’s grains and weakens the bonds holding those grains together. The metal is intact chemically but has lost the cohesion that made it strong.

Going further

  • Re-use it forever. Because it re-melts at ~30 °C, one lump of gallium can be cast and melted indefinitely — compare it with titanium, a metal at the opposite extreme of the melting-point scale.
  • Low-melting alloys. Adding indium and tin to gallium gives galinstan, a metal liquid at room temperature and a non-toxic stand-in for mercury.