Enduring Bronze -
The Metal of the Ages
Traditional Bronze is a copper alloy with up to 10% tin. The
tin in bronze makes it more resistant to wear than unalloyed
copper. Bronzes today are usually stronger and more resistant
to corrosion than brass.
Contemporary bronzes are typically copper alloys that may
contain silicon, manganese, aluminium, lead, iron and other
elements, with or without tin.
The variations in bronze composition significantly affect its
characteristics. Durability, machine ability,
corrosion-resistance and ductility for deep drawing are often
|Bronze Grade A 5%
Copper - Tin alloy
from 3% tin (mild bronze) to 25% tin (bell metals)
The first metal used by man was copper so it is natural that the
first alloys widely used were copper alloys. The two alloys of
most significance are bronze and brass. Bronze is an alloy of
copper and tin, while brass is an alloy of copper and zinc.
Recently many objects, thought to be bronze, have been found to
be brass. Since the patina and color of bronze and brass are
almost indistinguishable from each other.
All copper-tin alloys with more than 78% copper are called
bronzes. They are chemically very stable. When in dry air the
metal does not change at all, while in moist air they produce a
beautiful, green, pore-free, surface film (patina) which protects
the layers it covers from corrosion.
The tin content makes the alloy hard, bronzes with 6% tin can still
be rolled, or hammered, while bronzes with 10-20% tin are
usually require casting. Bronzes with more than 20% tin are used
for bell casting, these alloys are hard and rather brittle, but when
struck they emit a clear note. Even higher tin content (up to 40%)
produces radiantly white alloys; like the bell alloys these are
brittle and hard, but accept a beautiful polish. They were used for
bronze mirrors even in antiquity, and today are called speculum
Bronze was widely used for utilitarian and artistic purposes until
iron became cheaper and more plentiful. Bronze continued to
have wide utilitarian uses until it became cost prohibitive, now
except for a few applications as a bearing metal in the
engineering and automobile industries has fallen out of use.
Artistically bronze is still widely used in casting sculptures of all
sizes, plaques, and bell founding.
|Bronze Ingots ready to be fired.
|Our custom forged plaques
adorn homes, businesses,
schools, vacation retreats,
classrooms, clubs, docks,
airplane hangers, boats,
restaurants, taverns -
you name it!
Weathering and Patination:
The oxidation process that gives Bronze its
characteristic green patina is a result of exposure to
an acidic atmosphere. The process is, therefore,
faster in some metropolitan, marine, and industrial
areas, where higher concentrations of pollutants exist.
When acidic moisture comes in contact with exposed
Bronze surfaces, it reacts with the copper to form
copper sulfate. The acid is neutralized during the
reaction with the copper. This patina eventually covers
the surface and adheres tightly to it, thus providing a
protective layer against further weathering.
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Bronze was the first alloy intentionally manufactured and used by
man. Early bronze was an alloy of copper and arsenic that occur
together naturally, and was used from about 4,000 BC until about
3,500 BC. While we do not really know, the copper-arsenic alloys
probably fell of favor because:
1. They were unpredictable in composition, giving unpredictable
properties to the finished product.
2. The smelting process releases arsenic gas, probably killing the
metalworkers and causing the uses to think the metal was evil.
About 3,500 BC true bronze started to appear. This true bronze
was harder and less brittle than copper-arsenic bronzes, could be
made copper and tin ingots if the natural materials were not
available, and could be made the same every time.