Brass, gold, and bronze are metals or metal alloys that can often be confused by the untrained eye due the similar nature of their coloring. Here, we will help you gain the knowledge to be able to differentiate between them on your own. First, we will explore the individual characteristics of brass, gold, and bronze. Next, we’ll follow up by providing information about various tests that can be performed, to make sure you know the exact type of metal or metal alloy with which you are working.
Characteristics of Brass
Brass is an alloy made of copper and zinc (usually in a respective 67% to 33% ratio) known for its ability to last a long time and take different shapes. (Before zinc was discovered, brass was created with the combination of copper and calamine— an ore of zinc.) Brass can be categorized into different classes based on the ratios of copper and zinc (even though, as mentioned above, the 67% copper to 33% zinc ratio is the most common). The different types of classes of brass are as follows: Alpha Brass, Alpha-Beta Brass or Duplex Brass, Beta Brass, and White Brass.
An item being referred to as “solid brass” refers to the fact that it is made of pure brass material, not that the shape of the piece itself has to be solid. Meanwhile, a thin film of brass covering a piece is referred to as “plated brass”. It is useful to note that cleaning of plated brass is much more difficult than if the piece is solid brass.
Another helpful characteristic to know about brass is that the exact color of brass depends on the ratio of copper and zinc. It can vary from a pure copper color, to white or yellow, as per the ratio. Most brass shouldn’t tarnish easily.
Additionally, brass is not a magnetic metal alloy. It weighs 8.4-8.73 grams per centimeter, has a low melting point of 900-940 o C, and is low friction. Common items created out of brass include musical instruments, decorative fixtures, zippers, plumbing, and fireplace equipment. Items created out of brass are able to be recycled.
Characteristics of Gold
Gold is a chemical element that is part of the periodic table of elements., and therefore a metal. It has long been prized for its illustrious, yellow color, malleability, virtual indestructibility, and its prevalence in nature in a stable state. Gold is also one of the densest elements and conducts heat and electricity well. Likewise, it does not tarnish over time easily.
All of these qualities have made it stand out as a metal for almost all of human history. In fact, it is one of the only metals that has been accepted universally in exchange for goods. So much so, that it has served as a backing for entire paper-currency systems. It has also been found in ancient Assyrian, Egyptian, Etruscan, and Minoan artisan workmanship dating back thousands and thousands of years ago in elaborate and beautiful pieces that are still intact today.
Characteristics of Bronze
Bronze is an alloy traditionally made of both tin and copper. It has played a vital role throughout history—first originating around the year 3000 BCE— and is still widely used today. However, in more modern-day creations of bronze, it might be combined with zinc, manganese, or aluminum instead of tin. The specific metal with which it is mixed, as well as the proportions, affect its malleability and therefore its use too. Bronze’s most frequent applications are for tools, weapons, and coinage— with most “copper” coins are actually bronze, not pure copper, and contain about 2.5% copper with the rest being zinc.
Ways to Test for Metal Type
Besides understanding the individual characteristics of brass, gold, and bronze themselves, there are a number of standard tests that can be performed to help differentiate these metals and metal alloys.
What color is the metal?
The color of bronze and brass often varies across the piece, especially on raised bits or edges; so, if you see this differentiation, it is not pure gold. Gold is shinier and more yellow in tone than brass. Brass is duller and does not possess the same vibrancy. You can also check by taking a hidden part of the piece and filing it a bit. Gold would leave behind a gold streak, where brass or bronze would leave behind more of a black streak.
Does it smell metallic?
Brass is a metal that often has a metallic smell (meaning that the metal gives off a smell while oxidizing). Metals considered to be of a superior quality, such as gold, resist this oxidation and therefore are less likely to emit the smell. You can even try a simple, at home test of rubbing the piece between your fingers for a few moments and then smelling your fingers. If you detect that classic metallic scent, it would not be pure gold.
What is the weight of the metal?
Higher quality metals are usually heavier. Metals are often categorized in terms of the metal’s “gravity” which is a weight to volume measure. Cast rolled brass is 8.4-8.7 gravity, while bronze comes in at 7.4-7.9, and pure gold at 19.2. Refer to this chart for a full list the gravity of various metals. An easy at home test to try this out is to fill a cup to the very top with water. Next, add the piece you are trying to measure into the cup. Then, catch the water that spills over and weigh that water. After that, remove the piece and weigh it by itself. Finally, divide the weight of the piece by the weight of the water that you caught and measured. If the piece is brass, it will weigh around 8.4-8.7 times the weight of the water. Meanwhile, if it is in fact gold, it should weigh about 19.3 times more than the water.
Does the metal have a hallmark?
In countries with strict regulations on precious metals, such as the US & UK, real metals are typically branded with a hallmark to be able to make them easily identifiable. Gold, as a precious metal, would have a karat count. Brass would not; however, it might be marked just as “brass” somewhere on the piece. Do keep in mind though that metal from other areas of the world that are not as stringent with their regulations, so might not have an easily identifiable hallmark and would require other ways to determine the metal.
Purchase an acid test
Although they are not cheap and do not last forever, acid tests can help to differentiate base metals from higher quality metals. Be sure to take all safety precautions while handling an acid test, however, as they are dangerous to inhale or touch. Wearing rubber gloves and using proper ventilation are a must. We recommend a “3 acid” or “5 acid” test depending on your need.
Different metals melt at varying temperatures. So if you heat the piece up that you are trying to test, the temperature reading could help to indicate which type of metal it is. Together, understanding each metal or metal alloy’s individual characteristics, as well as knowing a variety of tests that can be performed, should allow you to differentiate between brass, gold, and bronze in your work.