Written by Daniel Mariotti
A quick history of brass and bronze. The discovery of bronze dates back to about 3500 BC and the Sumerians. It is harder than pure iron and resists corrosion, which made it a good candidate for weapons (kicked out by the development of steel alloys) and later sculpture.
Brass took a while longer to discover (around 500 BC). Since zinc is practically never found naturally in its pure state, to get brass, people realized that copper smelted with calamine – a zinc ore—produced a golden colored tarnish-resistant metal that was useful for all sorts of things due to its low melting point. Brasses can have varying amounts of zinc added to them and these variations produce a wide range of properties and color variation.
Both brass and bronze are alloys of copper which is where the difficulty to differentiate arises. However, the difference is what these materials are “mixed” with. Brass is copper and zinc (60-80% copper and 20-40% zinc) while bronze is copper and tin (80-90% copper and 10-20% tin/other materials).
The reason why artists typically choose to cast in bronze over brass is due to bronze’s fluidity when casting. Bronze captures the fine detail of a mold and is able to push itself in cavities with more success and less pitting than other metals; especially with its silicone additive.
Fluidity is defined as an empirical measure of the distance a liquid metal can flow in a specific channel (our shell material) before being stopped by solidification. It is the ability of liquid metal or alloy to flow freely, and feed a mold cavity and produce the desired contour before freezing occurs. Bronze is an easier metal to work with for artists when it comes to chasing and welding pieces together thanks to this. On the other hand, brass is a much more difficult metal to weld. This is due to the amount of zinc that it contains compared to bronze. It also tends to have a low melting point which affects how you work with it. When welding brass, it will jump to your electrode, causing you to constantly grind your tungsten to continue working. Here is a helpful chart on common metal melting points we found from onlinemetals.com.
How to Identify
To differentiate between the two, first take a look at the color. Brass has a lighter finish with a bright yellow sheen that mimics the look of a dull gold, while bronze has a much darker finish and looks almost always reddish brown. Over time brass tends to blacken due to the oxidation of its zinc component. Bronze patinas typically desaturate a little under certain conditions, typically when placed outdoors.
Durability. Bronze is tough and durable but doesn’t have the flexibility that copper does. It does withstand water, which makes it resistant to corrosion (that’s why we love it so much in sculpture). Brass is strong but not as durable. It is susceptible to corrosion and cracking and is not as flexible as bronze.
In general, brass is used in a lot more industrial processes than bronze, whereas bronze is a material for artists. Brass will give us door handles; bronze will give us the door itself. Typically brass is a sheet material that can be shaped, bronze is a casting material that is ideal for sculptures.