Alumina crucibles are a popular, low-cost choice for melting metals in the lab and small foundry — but only for the right metals. Because 99% high-purity alumina is chemically inert with most molten metals and rated to about 1600°C, it handles gold, silver, copper, aluminium and many alloys cleanly. This guide covers which metals you can melt in alumina, when to switch to graphite, zirconia or platinum, and how to melt without cracking the crucible.

Can you melt metal in an alumina crucible?

Yes — alumina is one of the most widely used crucible materials for melting metals, and for good reason. High-purity alumina (99% Al₂O₃) is chemically inert with most molten metals, has a high working temperature (~1600°C continuous), low porosity so the melt stays clean, and a low price. The single thing to check first is temperature: alumina works for any metal whose melting point sits comfortably below 1600°C, which covers the great majority of precious and common metals.

Which metals you can melt in alumina

Here is where the common metals land. As the chart above shows, nearly all sit safely inside alumina’s range.

• Gold (1,064°C) & silver (962°C): ideal — alumina is inert and contributes no contamination, giving a clean melt for casting and refining.
• Copper (1,085°C) & bronze/brass: a standard alumina application; well within range.
• Aluminium (660°C): easy — far below the limit, with no reaction.
• Steel & nickel alloys (<1,600°C): many carbon and stainless steels and nickel alloys melt below the limit and work in alumina; check your specific alloy’s liquidus.
• Platinum-group (1,768°C): near or above the limit — alumina is borderline; zirconia or a dedicated setup is safer.

Melting each metal: gold, silver, copper and more

The headline answer is “yes for most metals,” but each metal has its own practical notes. Here is how the common ones behave in an alumina crucible.

Melting gold in alumina

Gold melts at 1,064°C — comfortably below alumina’s limit. Alumina is inert with molten gold and adds no contamination, so it gives a clean melt for casting, refining and alloying. Use a conical crucible for easy pouring, and dedicate a crucible to gold to avoid cross-contamination with base metals. Gold’s high density means a small crucible holds a surprising mass, so size by weight, not just volume.

Melting silver in alumina

Silver melts at 962°C, the lowest of the common precious metals, and melts cleanly in alumina. The main practical point with silver is that molten silver readily absorbs oxygen and then releases it on solidifying (“spitting”), so melt under a cover or flux and pour promptly. Alumina’s inertness keeps the metal clean throughout.

Melting copper, brass and bronze

Copper melts at 1,085°C; brass and bronze melt lower depending on alloy. All are standard alumina applications, well within range. Copper oxidises readily when molten, so a cover or flux helps; alumina itself is unaffected. For repeated copper-alloy casting, alumina’s reusability makes it economical.

Melting aluminium

Aluminium melts at just 660°C — far below the limit — so alumina handles it easily. Note that molten aluminium is reactive and can slowly attack many materials over long holds; for routine melting and casting alumina performs well, but keep holds reasonable and avoid contaminating the melt with the wrong flux.

Melting steel, nickel and higher-temperature alloys

Many carbon and stainless steels and nickel alloys have liquidus temperatures below 1,600°C and can be melted in alumina — always check your specific alloy’s melting range first. For alloys at or above 1,600°C, alumina creeps near its limit, so switch to zirconia or an induction setup designed for the temperature. Iron-rich melts at the top of the range push alumina hard, so treat 1,600°C as a firm ceiling, not a target.

Why alumina works well for melting

Three properties make alumina a strong default for metal melting. First, chemical inertness: it does not react with most molten metals, so it neither contaminates the melt nor degrades quickly. Second, no carbon pickup: unlike graphite, alumina adds nothing to the metal, which matters for clean precious-metal and oxidising melts. Third, cost and availability: alumina crucibles are inexpensive and come in every shape and size, so you are not paying a premium for capability you don’t need.

For pouring and easy melt recovery, the tapered conical alumina crucibles are popular for melt work, while cylindrical crucibles suit bench-top melting. Browse the full alumina crucible range to match a size to your furnace.

Alumina vs graphite for melting

Graphite is the other common melting crucible, so it is worth knowing when each wins. Graphite conducts heat extremely well for fast, even melts and tolerates very high temperatures — but it burns in air, so it needs an inert or reducing atmosphere, and it can carburise (add carbon to) sensitive metals. Alumina is fully stable in air, adds no carbon, and is the cleaner choice for oxidising melts and precious metals — at the cost of slower heat transfer and more care against thermal shock.

The rule of thumb: choose alumina for clean, oxidising or precious-metal melts where carbon contamination is unacceptable, and graphite for fast melting under inert gas where carbon pickup is tolerable. For the wider material picture, see our crucible material selection guide.

Melting atmosphere: oxidising vs inert

The furnace atmosphere shapes both the melt and the crucible choice. In an oxidising atmosphere (open air), alumina is fully stable — this is where it beats graphite, which would burn. The trade-off is that some molten metals (copper, silver) pick up oxygen in air, so a cover, lid or flux protects the melt while the alumina crucible stays unaffected. In an inert atmosphere (argon, nitrogen) or under vacuum, both alumina and graphite work, and you would pick based on speed (graphite) versus cleanliness (alumina). For oxidation-sensitive or reactive metals, melting under inert gas in alumina gives the cleanest result. A close-fitting alumina cover reduces oxidation and heat loss whichever atmosphere you use.

Choosing the right crucible size

Size the crucible to the mass of metal, not just its volume — dense metals like gold need far less crucible than the same mass of aluminium. Work out the volume your charge occupies when molten and pick a crucible that fills to no more than about two-thirds, leaving headroom so the melt cannot spit or overflow when stirred or poured. Allow extra room if you add flux or top up mid-melt. A crucible that is too large wastes energy heating empty ceramic; one that is too small risks spillage and crucible stress. Labmina’s cylindrical and conical ranges span small bench volumes up to several litres — check the size charts to match your charge and furnace.

When NOT to use alumina

Alumina is the default, not a universal answer. Reach for another material when:

• Your melt exceeds ~1600°C. Above alumina’s working limit it creeps and deforms — use zirconia (~2000°C) or platinum.
• You run reactive alkali fluxes or strong bases. These corrode alumina; zirconia or platinum resist them. See alumina vs zirconia.
• You melt metals that attack alumina. Certain reactive molten metals and some fluxing conditions degrade it — verify compatibility for unusual alloys.
• You need the fastest possible conductive melt under inert gas — graphite’s conductivity wins there.

How to melt metal without cracking the crucible

Most crucible failures in melting come from thermal shock and handling, not the metal. A few habits make alumina crucibles last:

• Condition a new crucible. Fire it empty once to working temperature before its first melt to stabilise it.
• Ramp gradually. Heat and cool at a controlled rate — alumina has only moderate thermal-shock resistance, so avoid sudden changes.
• Never quench a hot crucible. Don’t set it on a cold surface or expose it to a draft straight from the furnace.
• Don’t overfill. Leave headroom so the melt can’t spit or overflow.
• Match crucible to metal. Don’t reuse a crucible across incompatible metals; cross-contamination ruins both melt and crucible.
• Support the crucible properly with the right tongs and base to avoid mechanical stress when full and hot.

Melting safety

Molten metal is dangerous; treat every melt with respect. The essentials:

• PPE: heat-resistant gloves, face shield, apron and closed footwear. Molten-metal splash causes severe burns.
• Ventilation: melt under a fume hood or with strong ventilation — metal fumes and flux vapours are hazardous (zinc, lead and cadmium fumes especially).
• Dry everything: any moisture on tools, metal or the crucible can flash to steam and cause a violent ejection of molten metal. Pre-heat additions.
• Use matched tongs and a pouring shank that grip the crucible securely; never lift a full hot crucible with improvised tools.
• Clear, fireproof pour path: set up moulds and route before heating, on a non-flammable surface, with no clutter underfoot.
• Keep water away from the melt area entirely.

Common mistakes when melting in alumina

• Assuming it handles any temperature. Check your metal melts below ~1600°C before choosing alumina.
• Quenching or thermal-shocking the crucible — the number-one cause of cracks.
• Running alkali fluxes in alumina — they corrode it; switch to zirconia or platinum.
• Cross-contaminating metals by reusing one crucible for incompatible melts.
• Using graphite for an oxidising or carbon-sensitive melt — that’s where alumina is the right call.

Conical — easy pour

Cylindrical — bench melt

Rectangular — batch

Conclusion

For melting gold, silver, copper, aluminium and most sub-1600°C alloys, a 99% high-purity alumina crucible is an excellent, economical choice — inert, clean and reusable. Step up to zirconia or platinum only above 1600°C or for aggressive fluxes, and choose graphite when you need a fast conductive melt under inert gas and can tolerate carbon. Whatever you melt, ramp gradually to protect the crucible. Browse the alumina crucible range, read the material selection guide, or request a custom size for your furnace.

Frequently asked questions