Silver has the highest electrical conductivity and the highest thermal conductivity of any metal. In this respect it is the best contact material available. It is, however, rarely recommended for use in light-duty applications because of its tendency to tarnish.

The voltage at heavier duties is normally sufficient to break down these sulphide films so that their presence does not affect contact performance.

The addition of copper to Fine Silver has the beneficial effect of increasing hardness and arc-resistance. These alloys have better anti-welding properties for applications up to 100A, but are not as good as Silver-Nickel on “make”. At the same time, however, contact resistance increases as does tarnishing.

Material Density g/cc Annealed Hv Solidus (°C) Electrical Conductivity %IACS Electrical Resistivity u.cm
Fine Silver (99.99%) 10.5 26 962 107 1.59
Fine Silver (99.97%) 10.5 26 962 106 1.6
Fine Silver (99.9%) 10.5 26 962 106 1.6
Contact Grade Silver 10.5 30 960 95 1.8
Silver 3% Copper 10.4 65 900 91 1.9
Silver 7.5% Copper 10.4 75 800 86 2.0
Silver 10% Copper 10.3 80 779 86 2.0
Silver 20% Copper 10.2 85 779 86 2.0
Silver 28% Copper 10.0 100 779 82 2.1
Silver 50% Copper 9.7 110 779 82 2.1