Freezing point for gold: Pure vs. 14k Alloy Differences

The freezing point of pure gold is the same as its melting point: 1,064.18°C (1,947.52°F, 1,337.33 K). For a pure element, melting and freezing are the same phase transition — gold melts as you heat it past 1,064°C and freezes as you cool it below 1,064°C. The direction of crossing does not change the temperature.

For gold alloys — 14k, 18k, 22k — the answer is more complex and more practically important. Alloys freeze over a range of temperatures rather than at a single point, and the range widens as the alloy’s purity decreases. A 14k gold alloy might begin solidifying at 880°C and not complete solidification until 820°C — a 60°C spread that determines everything about how the metal behaves during casting.

This article covers the freezing-point data for pure gold and every common commercial gold alloy, explains the physics of why alloys freeze over ranges while pure elements freeze at points, and addresses the practical implications for jewelry casting, dental laboratory work, and precious metal refining.

Freezing Point for Pure Gold: The Reference Value

The freezing point (solidification temperature) of pure 24-karat gold is identical to its melting point:

Source: NIST Standard Reference Database — this is the ITS-90 fixed point value, the internationally agreed calibration reference for high-temperature thermometry in the 1,000–1,200°C range.

Why melting point equals freezing point for pure gold: Pure gold undergoes a sharp, reversible phase transition at 1,064.18°C. Heating above this temperature breaks down the face-centered cubic (FCC) crystal lattice — the solid melts. Cooling below this temperature allows atoms to organize into the FCC lattice — the liquid freezes. At exactly 1,064.18°C under equilibrium conditions, solid and liquid gold coexist indefinitely — this is the definition of the transition temperature.

The latent heat of fusion for gold is 12.55 kJ/mol. During freezing, this heat must be released before solidification is complete. In a well-controlled calorimeter, the temperature remains perfectly constant at 1,064.18°C while the latent heat is released — producing the temperature plateau that makes gold a primary calibration fixed point on the ITS-90 scale.

Practical precision: In a manufacturing context (casting, soldering), you will see gold’s freezing point cited as 1,064°C / 1,948°F — rounded from the precise scientific value. For jewelers and casters, the rounded value is entirely adequate.

Why Gold Alloys Have a Freezing Range Instead of a Freezing Point

Pure gold freezes at a single temperature. Any gold alloy — 22k, 18k, 14k, or 10k — freezes over a temperature range. Understanding why requires the concept of the liquidus and solidus.

Liquidus and solidus in gold alloys

When a gold alloy cools from the liquid state, it passes through three stages:

Above the liquidus temperature: The alloy is entirely liquid. All alloying elements (copper, silver, zinc, palladium) are dissolved in the gold melt.

Between liquidus and solidus (the “mushy zone”): As the alloy cools below the liquidus, gold-rich crystals begin to form and grow. The remaining liquid becomes progressively richer in the alloying elements (copper, silver, zinc), which have lower melting points and are therefore left behind as the gold-rich phase crystallizes first. During this stage, solid and liquid coexist simultaneously. The alloy is neither fully liquid nor fully solid — it is partially molten.

Below the solidus temperature: The alloy is completely solid. Solidification is complete.

The gap between liquidus and solidus temperatures is the freezing range of the alloy. For pure gold: 0°C (freezes at a single point). For a 14k yellow gold alloy: typically 60–80°C (freezes over a range).

Why the freezing range matters for casting

The mushy zone creates practical problems in casting:

Shrinkage porosity. As the solid phase grows within the mushy zone, it contracts. The liquid that should feed this shrinkage must flow through a partially solidified network. If the freezing range is wide, this network blocks flow before shrinkage is fully compensated, causing internal voids (porosity) in the casting.

Feeding requirements. Wide freezing-range alloys require larger risers (reservoirs of liquid metal) and more careful gating design to ensure liquid metal can feed solidification shrinkage throughout the mushy zone.

Segregation. During solidification through a wide range, the early-forming gold-rich crystals are compositionally different from the last-to-solidify alloy. This composition gradient (coring or dendritic segregation) can affect mechanical properties, color consistency, and corrosion resistance across a single casting.

Freezing Point Range by Gold Alloy: Complete Reference Table

Pure gold and high-karat alloys

The high-karat alloys (22k–23k) have relatively narrow freezing ranges because the dominant element (gold, >90%) controls the liquidus, and the small quantities of alloying elements produce only modest depression of the solidus.

Commercial jewelry alloys

Source: ASM Handbook, Volume 2; ISO 9202:2014, Jewellery — Fineness of precious metal alloys.

Key observations from this table:

The 14k gold freezing point is a range, not a number. Standard 14k yellow gold (58.3% Au, balance Cu-Ag-Zn) completes its freezing between approximately 820°C (solidus) and 880°C (liquidus) — a 60°C range. The “freezing point of 14k gold” is 820°C if you mean the temperature at which solidification is complete, and 880°C if you mean the temperature at which it begins. Both temperatures are important for the caster.

White gold alloys have different freezing ranges than yellow gold of the same karat. Palladium-based 18k white gold (solidus ~930°C) has both a higher solidus and a narrower freezing range than nickel-based 18k white gold (solidus ~890°C). The composition — specifically, which elements are used to achieve the white color — significantly changes the solidification behavior.

Lower karat = lower solidus = wider freezing range. This trend is consistent across the table. As gold content decreases, the more refractory gold is replaced by copper, silver, and zinc (all lower-melting), and the freezing range widens because the liquidus and solidus diverge further on the gold-copper-silver phase diagram.

The Physics Behind Gold’s ITS-90 Fixed-Point Status

Pure gold’s 1,064.18°C freezing point is not merely a data point — it is one of the defining fixed points of the International Temperature Scale of 1990 (ITS-90), the basis for all high-precision thermometry worldwide.

Three Group 11 metals — silver (961.78°C), gold (1,064.18°C), and copper (1,084.62°C) — provide three closely spaced calibration reference points in the critical 950–1,100°C range. These three points together enable thermometer calibration at 100°C intervals across the range most relevant to precious metal processing, glass working, and high-alloy steel heat treatment.

Why is pure gold used, not gold alloy

A calibration fixed point requires a sharp, reproducible transition temperature. Pure gold, as a single-element system, has exactly this: a single freezing point that is determined solely by the Au-Au interatomic interactions and is the same for any sample of 99.999%+ purity anywhere on earth.

Gold alloys have a freezing range rather than a fixed point — making them unsuitable as calibration references. The 60°C range of 14k yellow gold means there is no single temperature at which a calibration observation can be made.

In ITS-90 laboratory practice, a high-purity gold sample (99.999%+, approximately $2,000–$5,000 worth of gold in a calibration cell) is melted and then allowed to freeze slowly. The plateau produced by the latent heat release is measured. Any deviation from 1,064.18°C indicates thermocouple drift and can be corrected — enabling thermometry traceability to national standards with uncertainty of ±0.1°C or better.

Freezing Point in Gold Casting Practice

For jewelers, dental laboratory technicians, and precious metal casters, the freezing-point data translates directly into casting practice decisions.

Pour temperature: above the liquidus

Casting metal must be poured at a temperature above the liquidus to ensure complete mold fill before solidification begins. Standard casting temperatures are set at the liquidus plus 50–100°C of superheat:

Pouring below the liquidus produces misruns (incomplete fill) and cold shuts (visible seam lines where two flow fronts meet before joining). Pouring too far above the liquidus increases metal oxidation, increases gas absorption (particularly hydrogen from investment moisture), and increases solidification shrinkage.

Solder and repair: below the solidus

When soldering or repairing a gold casting, the solder must flow below the solidus of the base metal. If the torch temperature exceeds the base metal’s solidus, the base metal surface begins to melt — causing collapse, distortion, or loss of surface detail.

For 14k yellow gold (solidus 820°C), the solder joint temperature must remain below 820°C. Standard 14k easy gold solder has a liquidus of approximately 730–770°C, providing a 50–90°C safety margin below the base metal solidus. “Hard” solder with a liquidus around 790°C narrows this margin and requires precise torch control.

The practice of assembling complex pieces using solder grades with progressively lower liquidus temperatures — hard solder first, medium solder for subsequent joints, easy solder last — is directly governed by the need to stay below the solidus of previously assembled joints.

Frequently Asked Questions About the Freezing Point of Gold

Q: What is the freezing point of gold?

For pure 24-karat gold: 1,064.18°C (1,947.52°F, 1,337.33 K). This is identical to the melting point — for a pure element, melting and freezing occur at the same temperature. This value is the ITS-90 international calibration reference.

Q: What is the freezing point of 14k gold?

14k yellow gold freezes over a range rather than at a single point. The liquidus (where freezing begins) is approximately 880°C (1,616°F); the solidus (where freezing is complete) is approximately 820°C (1,508°F). The full solidification range spans about 60°C. For casting practice, the pour temperature is set above the liquidus (~930–960°C); the repair solder must remain below the solidus (~820°C).

Q: Why does 14k gold have a different freezing point than 24k gold?

Because 14k gold is an alloy containing copper, silver, and zinc alongside the 58.3% gold content. In an alloy, the different elements freeze at different temperatures according to their position on the phase diagram. Gold-rich crystals form first (at the liquidus, ~880°C); the remaining elements concentrate in the liquid phase; freezing is not complete until all components have solidified (at the solidus, ~820°C). Pure gold freezes at one point; the alloy freezes over a range.

Q: Are the freezing point and melting point of gold the same?

For pure gold, yes — exactly 1,064.18°C. The melting point (solid → liquid) and freezing point (liquid → solid) are the same temperature for any pure element at thermodynamic equilibrium. For gold alloys, both a melting range and a freezing range exist — the liquidus and solidus temperatures are the same whether you are heating or cooling, but the transition spans a range rather than occurring at a single temperature.

Q: How does the cooling rate affect gold alloy solidification?

Faster cooling produces finer grain structure (smaller dendrites, less segregation) but can increase residual stress and reduce ductility. Very rapid cooling can kinetically suppress the equilibrium solidification path, producing metastable microstructures. In investment casting, the mold temperature and metal pour temperature together determine cooling rate — and therefore grain size, porosity distribution, and mechanical properties of the casting. Most jewelry casting targets a moderate cooling rate that balances fine-grain structure against thermal stress risk.

Q: Does the freezing point of gold change with karat?

Yes. The solidus temperature decreases as karat decreases: pure gold solidus = 1,064°C; 22k ≈ 985°C; 18k yellow ≈ 880°C; 14k yellow ≈ 820°C; 10k yellow ≈ 795°C; 9k yellow ≈ 780°C. The liquidus also decreases with karat, but the freezing range (liquidus minus solidus) typically widens as more alloying elements are added to lower-karat alloys.

References

1. National Institute of Standards and Technology (NIST), NIST Standard Reference Database 69: NIST Chemistry WebBook, available at webbook.nist.gov. (Gold freezing point as ITS-90 fixed point: 1,064.18°C / 1,337.33 K; latent heat of fusion 12.55 kJ/mol; the authoritative source for the precise gold freezing temperature cited as the international calibration reference.)
2. ASM Handbook, Volume 2: Properties and Selection — Nonferrous Alloys and Special-Purpose Materials, 10th Edition. ASM International, Materials Park, OH, 1990. (Liquidus and solidus temperatures for gold alloys by karat and composition; freezing range data for 14k, 18k, and 22k yellow and white gold alloys; casting temperature guidelines for commercial gold jewelry alloys.)
3. ISO 9202:2014, Jewellery — Fineness of precious metal alloys, International Organisation for Standardization, Geneva. (Karat and fineness definitions for gold alloys; minimum gold content requirements by karat designation; the international standard that defines what “14 karat” and “18 karat” mean — and therefore what the alloy compositions in the freezing range table contain.)
4. Haynes, W.M., ed., CRC Handbook of Chemistry and Physics, 104th Edition. CRC Press, Boca Raton, FL, 2024. (Pure gold physical constants: melting/freezing point 1,064.18°C; latent heat of fusion; ITS-90 fixed point description and calibration protocol; silver and copper fixed points at 961.78°C and 1,084.62°C cited in the calibration section.)

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Dr. Liu Che

Dr. Liu Che holds a Ph.D. in Engineering from Dalian University of Technology and completed postdoctoral research at the Mechanical Engineering Postdoctoral Fellowship of Harbin Institute of Technology. His research focuses on core algorithms for large-scale laser equipment integration, laser cladding remanufacturing, and real-time intelligent monitoring systems for processing. He possesses profound academic expertise in cutting-edge fields such as laser beam spatial shaping and the mechanism analysis of laser processing of special alloys. He has led numerous solutions to technical challenges in cutting and surface modification of high-hardness materials in the heavy machinery industry, demonstrating strong theoretical foundations and outstanding engineering implementation capabilities.

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