Metals react differently to oxygen exposure. Ferrous (iron-containing)
metals, for instance, form iron oxide or rust when exposed to air or moisture.
Non-ferrous metals such as copper and tin, on the other hand, develop a layer
of stain called patina.
This change in properties and compositions actually reduces the metal’s
overall quality. In the case of ferrous metals, it could even be worse, because
rust can reduce them to dust over time, rendering them unsuitable for use as
structural reinforcement. The patina on non-ferrous metals, however, has a different
effect. Instead of damaging the inside of the metal, it actually shields it
against corrosion.
One metal that is particularly susceptible to patination is bronze. An
alloy of copper and tin (both form patina when they oxidize), bronze develops a
layer of copper oxide on its surface fast, which later transforms into a much
harder material, called copper carbonate. Although it seems like a
disadvantage, in certain applications of bronze, this property can actually be
a merit. Take sculpture for example.
Bronze
Used in Sculpture
For thousands of years, bronze has been tortuously sculpted into
statues, ornaments, and accessories. The bronze sculptures made millennia ago
can still be seen intact in museums all over the world, thanks to their thick
layers of patina. It would take more than a couple more millennia for their
patina to completely whittle away at the interior of these bronze artifacts.
Sculpting with bronze is still popularly practiced today, and this is
mainly due to bronze’s amazing properties. It is hard but slightly brittle,
which makes removing portions of the metal without cracking or chipping it
quite possible and easy. The patina, which gives the final output an antique
appearance, becomes part of the package.
Artificial
Patina
Bronze’s unique patina has become so coveted that some have invented
techniques for speeding up its development. Generally called “intentional
patination”, these techniques involve the use of a variety of chemicals to
achieve a precise surface color. Sculptors usually apply these chemicals in a
number of layers to produce varied effects, and depending on the chemical used,
the resulting patina can be transparent or opaque.
Originally performed to confer the appearance of
antiquity on sculptures, intentional patination helps prevent bronze from
developing a different kind of patina, which usually does not contribute beauty
to the sculpture’s appearance. Controlling the process allows for the creation
of the most beautiful bronze furniture and ornaments.
Of course, the success of intentional patination still depends on the
purity of bronze used. If you are looking to make your own bronze sculpture or
ornament and you want to achieve a certain antique appearance through
patination, make sure to get your supplies from a company that has been
providing high-quality bronze materials for decades. Suppliers like Rotax
metals can provide you with the highest quality bronze tube, bar, or sheet for
your project.
About
Rotax Metals: Rotax Metals is North America’s leading
provider of copper, brass, and bronze supplies. We cater to builders, artisans,
manufacturers, and metal suppliers across the U.S. and Canada. Established in
1948, we’ve been the supplier of choice for small and large businesses, simply
because we are fully capable of exceeding expectations. We leverage our vast
knowledge in metalwork and fully equipped manufacturing facilities to provide
only the best materials that could suit any type of project.
Sources:
The Artificial Patination of Bronze Sculpture
What Is Patina? Definition and Uses
Patina Formulas for Brass, Bronze and Copper
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