Copper is a pure metal, so every object made with this material has more or less similar properties; brass, on the other hand, is an alloy of copper, zinc and often other metals. The hundreds of different combinations make it impossible to develop a unique and foolproof method for recognizing all brass. That said, the color of this alloy is usually distinctive enough to distinguish it from copper.
Steps
Method 1 of 2: Recognizing Brass Through Color
Step 1. Clean the metal if necessary
Over time, both copper and brass develop a patina that is usually green, but can take on other shades. If you can't see any portion of the original metal, try one of the techniques described in this article, which are typically effective for both materials; in order not to risk, however, you can use a commercial product specific for copper and brass.
Step 2. Hold the metal under a white light
If the surface is very shiny, you may see false colors due to reflected light. Look at it in sunlight or near a white fluorescent light bulb and not a yellow incandescent one.
Step 3. Recognize the reddish color of copper
It is a pure metal that always has a red-brown color. The 1, 2 and 5 euro cent coins are copper-plated, so they can become a good reference for comparison.
Step 4. Inspect the yellow brass
The term brass refers to an alloy that contains copper and zinc and its final color varies according to the proportion of the two metals. However, in most cases brass has a faint yellow or yellow-brown color similar to bronze. Brass alloys are widely used to make screws and mechanical parts.
In some cases, the brass takes on a greenish-yellow color, but it is a particular alloy with a very high mechanical resistance, which is used only for decoration or for ammunition
Step 5. Learn about red or orange brass
Many other common alloys take on an orange or reddish-brown hue because they contain at least 85% copper; they are used in the production of jewelry, decorative buckles or in pipes. Any hint of orange, yellow or gold indicates that the material is brass and not copper. If the alloy is almost entirely made of copper, you need to visually compare the object to a pure copper tube or piece of costume jewelry. If you still have doubts, it could be both copper and brass with such a high percentage of copper that any distinction is useless.
Step 6. Recognize other types of brass
Those that contain a lot of zinc have a bright golden color, a yellowish-white hue and even white or gray. These are uncommon alloys, as they are not machinable, but you can encounter them in jewelry items.
Method 2 of 2: Use other Recognition Techniques
Step 1. Hit the metal and listen to the sound it produces
Since copper is quite soft, it produces a dull, rounded sound. An old test conducted in 1867 defined the sound emitted by copper as "dead", while that of brass is "a clear ringing note". It's not easy to tell the difference if you're inexperienced, but learning this method could be useful for people with an antique or collecting hobby.
This method works best with thick solid metal objects
Step 2. Look for engraved marks
Brass objects made for industrial purposes often have an engraved or printed code, which makes it possible to identify the exact composition of the alloy. The coding criteria for brass are the same for both North America and Europe and require an acronym with the letter C followed by several numbers. Copper hardly shows any sign of recognition, but if you want to be sure, compare the mark you read on the item with those on this short list:
- The UNS system in force in North America uses codes starting with C2, C3 or C4 or falling within the range from C83300 to C89999. Copper, if marked, has codes between C10100 and C15999 or between C80000 and C81399, although the last two digits are often omitted.
- The current European system provides for a code starting with "C" for both copper and brass; however, brands referring to the alloy end with the letters L, M, N, P and R, while those for copper end with A, B, C or D.
- Antique brass items may not bear these codings. Some old European standards (sometimes still in use) provide for the use of the chemical symbol of each element followed by the percentage. Anything that contains "Cu" (copper) and "Zn" (zinc) is considered brass.
Step 3. Check the hardness of the material
This test is typically not very useful, as brass is only slightly harder than copper. Some types of treated copper are particularly malleable, so you are able to scratch them with a dime (which is impossible to do with any brass alloy). However, in many cases it is not possible to have an object that is capable of scratching one material, but not the other.
Copper bends more easily than brass, but it is difficult to draw exact conclusions from this test (especially without damaging the object)
Advice
- Copper is a better conductor than brass, reddish electrical wires are therefore made of copper.
- In some cases, the terms "red brass" and "yellow brass" used in the metallurgical industry indicate a specific material, but in this article they have been used only to describe colors.
- Almost all the musical instruments defined "brass" are made of brass and not copper. The higher the copper content in the alloy, the warmer and deeper the sound emitted by the instrument. Copper is used for some wind instrument components, but it doesn't seem to affect the sound.
