Authoritative Engineering Standards Reference • 8 Verified Grades

Grades of Silver: Purity, Fineness & Engineering Properties

A rigorous metallurgical analysis of standardized silver alloys classified under the international millesimal fineness system (ISO 9202, ASTM B742, DIN 17510). Covers composition limits, density variation, electrical conductivity, mechanical yield strength, precipitation hardening, and industrial applications.

The Millesimal Fineness System Explained

Unlike structural carbon steels (classified by carbon hundredths in SAE/AISI systems) or aluminum alloys (designated by 4-digit composition series), precious metals are globally standardized using millesimal fineness. Fineness denotes the proportion of pure elemental silver contained within an alloy expressed in parts per thousand (‰) by weight.

Pure / Fine Standard (999)

Contains ≥ 999.0 parts pure silver per 1,000 (99.9% min). Characterized by high ductility, peak conductivity (106% IACS), and low yield strength (55 MPa).

Standard Sterling (925)

Comprises 925 parts pure silver and 75 parts copper (92.5% Ag). Copper additions double annealed yield strength (135 MPa) and enable precipitation hardening.

Alloyed & Eutectic Grades (800–900)

Containing 10% to 20% copper. Moving closer to the Ag-Cu eutectic (71.9% Ag at 779°C), these alloys maximize hardness (100 HV annealed) and wear resistance.

Master Silver Grades Comparison Table

All values verified against ASTM B742, ISO 9202, DIN 17510, and ASM International data. Click any grade for its full material specification.

Grade	Fineness	Ag Min	Alloying Solute	Density	Conductivity	Yield (Ann.)	Hardness (Ann.)	Primary Standard
Fine Silver 999	999	≥ 99.90%	Unalloyed (trace Cu, Pb, Fe < 0.1%)	10.49 g/cm³	106% IACS	55 MPa	28 HV	ASTM B742 Grade 99.90
Silver 970	970	97.00%	3.0% Copper (Cu)	10.43 g/cm³	96% IACS	75 MPa	45 HV	ISO 9202: 970
Britannia Silver 958	958	95.84%	4.16% Copper (Cu)	10.40 g/cm³	92% IACS	90 MPa	55 HV	UK Hallmarking Act 1973 (958)
Silver 950	950	95.00%	5.0% Copper (Cu)	10.38 g/cm³	90% IACS	105 MPa	60 HV	French 1st Standard (Minerve 1)
Sterling Silver 925	925	92.50%	7.5% Copper (Cu)	10.36 g/cm³	84% IACS	135 MPa	70 HV	ASTM B742 Grade 92.5
Silver 900	900	90.00%	10.0% Copper (Cu)	10.31 g/cm³	78% IACS	160 MPa	80 HV	UNS P07900
Silver 835	835	83.50%	16.5% Copper (Cu)	10.22 g/cm³	72% IACS	195 MPa	90 HV	DIN 17510 (Ag835 / 2.3835)
Silver 800	800	80.00%	20.0% Copper (Cu)	10.15 g/cm³	68% IACS	215 MPa	100 HV	DIN 17510 (Ag800 / 2.3800)

Engineering Profiles by Silver Grade

999 Fineness

Fine Silver 999

Density: 10.49 g/cm³|Cond: 106% IACS|View Specs →

The purest commercially available silver grade. Highest electrical and thermal conductivity of any known metal at ambient temperature. Extremely soft and malleable in the annealed state with zero susceptibility to copper firescale.

Common Engineering Applications:

Electrical contactors, RF coaxial resonators, sputtering targets, high-purity crucibles

Governing Standards:

ASTM B742 Grade 99.90, ASTM B413, ISO 9202: 999, DIN 17510 Ag99.9

970 Fineness

Silver 970

Density: 10.43 g/cm³|Cond: 96% IACS|View Specs →

High-purity alloy providing 36% higher yield strength than fine silver while preserving a 96% IACS conductivity. Its low copper content prevents heavy copper oxide discolouration beneath transparent vitreous enamels.

Common Engineering Applications:

Vitreous enamelling substrate metal, precision low-force switch contacts, laboratory hardware

Governing Standards:

ISO 9202: 970, DIN 17510 Ag970, EN AgCu3

958 Fineness

Britannia Silver 958

Density: 10.40 g/cm³|Cond: 92% IACS|View Specs →

Established in England in 1697 to deter the melting of sterling coinage. Softer and substantially more malleable than sterling 925, enabling severe deep spinning and complex cold forming with fewer annealing cycles.

Common Engineering Applications:

Cold-spun pressure vessels, holloware, electrical contact rivets, decorative commemorative wares

Governing Standards:

UK Hallmarking Act 1973 (958), ISO 9202: 958, DIN 17510 Ag958

950 Fineness

Silver 950

Density: 10.38 g/cm³|Cond: 90% IACS|View Specs →

Traditional French 1st Standard alloy. Striking an optimal balance between cold ductility and structural rigidity, it provides higher stiffness than Britannia while maintaining higher malleability than sterling.

Common Engineering Applications:

Continental European precision holloware, sliding instrument contacts, luxury hardware

Governing Standards:

French 1st Standard (Minerve 1), ISO 9202: 950, DIN 17510 Ag950

925 Fineness

Sterling Silver 925

Density: 10.36 g/cm³|Cond: 84% IACS|View Specs →

The global reference standard for structural silver alloys. The 7.5% copper addition more than doubles the annealed yield strength of fine silver and introduces precipitation hardenable kinetics (up to 140 HV via heat treatment).

Common Engineering Applications:

Sliding switchgear, musical instrument tubes, surgical tools, multi-pin connector shells, high-wear assemblies

Governing Standards:

ASTM B742 Grade 92.5, ISO 9202: 925, UK Hallmarking Act 1973, DIN 17510 Ag925

900 Fineness

Silver 900

Density: 10.31 g/cm³|Cond: 78% IACS|View Specs →

Widely recognized as Coin Silver. Delivers exceptional sliding wear resistance and high cold-rolled hardness (165 HV) at a slight reduction in electrical conductivity compared to sterling.

Common Engineering Applications:

High-wear commutator contacts, slip ring brushes, historical pre-1965 US coinage, rotary switch wipers

Governing Standards:

UNS P07900, US Coinage Standard, ISO 9202: 900, DIN 17510 Ag900

835 Fineness

Silver 835

Density: 10.22 g/cm³|Cond: 72% IACS|View Specs →

Widely standardized across Central Europe (Germany, Austria, Netherlands). The 16.5% copper content creates a high-hardness two-phase matrix suited for repetitive electromechanical impact and sliding contact.

Common Engineering Applications:

Industrial relay contacts, mechanical detent springs, utilitarian tableware handles, wear hardware

Governing Standards:

DIN 17510 (Ag835 / 2.3835), ISO 9202: 835, Central European Hallmarks

800 Fineness

Silver 800

Density: 10.15 g/cm³|Cond: 68% IACS|View Specs →

The hardest and most wear-resistant common silver alloy. Lying adjacent to the silver-copper eutectic point (71.9% Ag at 779°C), it exhibits high yield strength (215 MPa annealed) and rapid work-hardening.

Common Engineering Applications:

Electromechanical breaker contacts, instrument gears, cutlery tines, stamped watch housings

Governing Standards:

DIN 17510 (Ag800 / 2.3800), French 2nd Standard (Minerve 2), ISO 9202: 800

Mechanical Strength & Work-Hardening Comparison

Silver and silver-copper alloys undergo pronounced strain hardening when subjected to cold rolling, drawing, or swaging. Fine Silver 999 exhibits a modest annealed yield strength of 55 MPa, which rises to 270 MPa after 50% cold reduction. In contrast, alloyed grades such as Sterling Silver 925 and Silver 800 reach yield strengths exceeding 390 MPa and 510 MPa respectively.

Grade	Yield (Soft Ann.)	Yield (50% Hard)	UTS (Soft Ann.)	UTS (50% Hard)	Hardness (Ann.)	Hardness (Hard)
Fine Silver 999	55 MPa	270 MPa	140 MPa	330 MPa	28 HV	95 HV
Silver 970	75 MPa	310-480 MPa	175 MPa	360-550 MPa	45 HV	105 HV
Britannia Silver 958	90 MPa	310-480 MPa	195 MPa	360-550 MPa	55 HV	115 HV
Silver 950	105 MPa	310-480 MPa	215 MPa	360-550 MPa	60 HV	125 HV
Sterling Silver 925	135 MPa	390 MPa	240 MPa	460 MPa	70 HV	160 HV (140 HV aged)
Silver 900	160 MPa	310-480 MPa	260 MPa	360-550 MPa	80 HV	165 HV
Silver 835	195 MPa	310-480 MPa	295 MPa	360-550 MPa	90 HV	175 HV
Silver 800	215 MPa	510 MPa	320 MPa	590 MPa	100 HV	185 HV

Tarnishing Chemistry & Atmospheric Behavior

Silver Sulfidation (Ag₂S)

Silver is chemically noble and does not oxidize in clean air at room temperature. Tarnishing is primarily caused by trace airborne hydrogen sulfide (H₂S) reacting with silver in the presence of oxygen:

4Ag + 2H₂S + O₂ → 2Ag₂S + 2H₂O

Silver sulfide forms a tenacious brown-to-black film. While Ag₂S has high electrical contact resistance, it is electrically conductive at high field strengths and can be readily wiped clean or electrochemically reduced without removing base metal.

Firescale & Copper Solute Oxidation

In alloyed silver grades (800 through 970), copper acts as a secondary oxidation site. At elevated temperatures (>500°C), atmospheric oxygen dissolves through the silver matrix, reacting preferentially with copper to create cuprous oxide (Cu₂O) particles:

4Cu + O₂ → 2Cu₂O

This subsurface oxidation is known as firescale. Because pure Fine Silver 999 lacks copper solute, it is completely immune to firescale defects during high-temperature annealing and brazing operations.

Curated Comparison

Fine Silver 999 vs Sterling Silver 925

Compare peak conductivity and softness of pure fine silver against the precipitation-hardenable mechanical strength of standard sterling.

Open Side-by-Side Comparison →

Conductivity Benchmark

Silver vs Copper Conductivity Comparison

Examine why silver (106% IACS) outperforms pure copper (100% IACS), evaluating RF skin depth, thermal dissipation, and economic trade-offs.

Compare Silver vs Copper Conductivity →

Silver Grades: Frequently Asked Questions

What is the millesimal fineness system for silver?

Millesimal fineness is a metallurgical system denoting the purity of precious metals in parts per thousand (‰) by weight. For example, 925 fineness represents 925 parts pure silver per 1,000 parts alloy (92.5% silver). This standard replaced historical fractional systems (like sterling ounces and pennyweights) and is formalized in ISO 9202.

How does alloying with copper affect silver density and conductivity?

Copper has a lower density (8.96 g/cm³) than silver (10.49 g/cm³). Therefore, increasing copper content systematically lowers alloy density from 10.49 g/cm³ (999) down to 10.15 g/cm³ (800). Concurrently, copper solute atoms introduce electron scattering centers in the silver FCC lattice, reducing electrical conductivity from 106% IACS in 999 silver to 84% in 925 sterling, and 68% in 800 silver.

Why is Sterling Silver 925 the most widely utilized engineering grade?

Sterling Silver 925 provides the optimum combination of high electrical conductivity (84% IACS), corrosion resistance, cold workability, and mechanical strength. Unlike fine silver, sterling can more than double its strength through cold work and is precipitation hardenable through heat treatment (solution anneal at 740°C–760°C and age at 280°C–300°C) to reach 140 HV.

What causes firescale in copper-alloyed silver grades?

Firescale is subsurface cuprous oxide (Cu₂O) formed when copper-bearing silver alloys (such as 925 or 900) are heated in oxidizing atmospheres during soldering, brazing, or annealing. Oxygen diffuses through the hot silver matrix and oxidizes the copper solute internally, creating a faint purplish-gray stain that requires mechanical abrasion or chemical pickling to eradicate.

Can Silver 800 be used for electrical contacts?

Yes. Silver 800 is extensively specified for heavy-duty industrial circuit breakers and electromechanical switches. Although its conductivity is lower than fine silver (68% vs 106% IACS), its high annealed hardness (100 HV) and resistance to arc erosion and mechanical fretting wear make it superior in repetitive high-cycle switching applications.