Bronze: The Definitive Guide to Understanding, Identifying & Care

Bronze is a metal that has been in use for thousands of years. Although modern bronze alloys are considerably more sophisticated than those found by archaeologists, this shiny brown metal is still revered and relied upon by many industries.

In this article, we’ll talk about the different types of bronze, what they’re commonly used for and how to get the most out of them.

What is Bronze? Understanding Bronze Composition and Properties

Bronze is not a naturally occurring element, but an alloy of two such elements: Copper and Tin. A typical composition is 88% copper and 12% tin, but other elements such as aluminium, manganese, zinc, and others are often added to increase certain properties.

The key properties of bronze are:

• Corrosion resistance
• Resistance to wear & low friction
• Hardness – when compared to copper
• Heat and electrical conductivity
• Ductility and ease of manufacture

Identifying Real Bronze: Key Characteristics and Tests

Bronze is often used for ornamental or decorative purposes, and as such, certain pieces are now valuable. This has created an incentive to replicate bronze with coatings on other metals or epoxy resin castings.

How to tell if an item is real bronze

• Sound: bronze has a sonorous quality, which means many objects give off a pleasant ringing sound when gently struck, unlike many other metals or any plastic/resin
• Non-magnetic: a plated steel or iron item will be magnetic, but bronze will not
• Weight: bronze has a higher density than steel, aluminium or epoxy products
• Hollow: bronze shrinks a lot when cooling, which means any larger cast items will usually be hollow, to make the manufacturing process easier

Bronze vs. Brass: Spotting the Differences

Brass is an alloy of copper and zinc, and as such shares some similarities with bronze, but telling them apart is relatively simple with some experience.

• Colour: bronze has a distinctly yellow tone, whilst brass is more brown/copper coloured
• Weight: Bronze has a higher density than brass, but this is generally only useful if you can accurately calculate the volume of each item

Caring for Bronze: Cleaning, Polishing, and Protecting

Bronze is often used for both architectural and ornamental purposes, such as detailing on building interiors, statues, and more. Through time, bronze tarnishes to a duller, but deeper colour. This is an oxidising process but only affects the very outer layer.

There are many commercially available products to clean and polish bronze but be careful to inspect the piece for any lacquer finish, as these need special attention when cleaning and polishing.

If your bronze antique is particularly special, seek advice before polishing it, as certain pieces can be devalued significantly if the age-old patina is removed.

How to protect bronze

If you have polished a bronze component or a new bronze item that is not protected, a clear lacquer or wax can help slow down the oxidation process.

Common metal polishes such as Brasso can help do this in a two-stage process, or a dedicated metal lacquer paint can be applied, but this will require careful care, planning and equipment.

Common Bronze Problems: Prevention and Solutions

Bronze is an incredibly useful material, but like any metal, careful consideration is needed before committing to using bronze for a component or part in service.

Shrinkage

Casting is a very popular way to make parts with bronze, thanks to its relatively low melting point and ability to produce detailed parts well. One of bronze’s key properties, however, is its high thermal expansion coefficient. This means the metal expands by a relatively large amount when heated.

This can pose an issue for casting processes, as parts can shrink when cooling, creating stresses and causing issues with parts that are designed to be flat or straight.

Bronze Disease

Bronze disease is a type of corrosion that affects almost all copper alloys, including bronze. The corrosive effect can be devastating to a part and is very difficult to stop.

Despite the name, bronze disease is not bacterial but caused by a chloride reaction with the copper in the metal. It is often seen in parts that have been buried in certain types of soil or exposed to seawater.

The typical process for protecting bronze from this type of corrosion is to tightly control the humidity and avoid any exposure to salt. If brass disease is found on any precious items, seek professional advice on cleaning them.

Be sure to keep any affected items separate from other bronze or brass, as the corrosion can be triggered and therefore “passed on” by the presence of the copper chloride dust produced.

Need bronze for your project?

If you need bronze bar, sheet, tube or more, head to the bronze section of our website to check out all the grades and thicknesses available. There you’ll find we offer a cut-to-size service and nationwide delivery.