Understanding Metal Density

Density is a concept to consider in addition to a metal's weight and hardness. Every material has a particular feel to it, a weight and a surface resistance. This feel is partially characterized by the density of the material. 

Density can be measured by its mass per volume, but it can also be understood in more familiar terms by understanding a material's specific gravity. Specific gravity is the ratio of a material's density with that of water. It is a relative (unitless) measure of the weight of a material. For example, gold has a specific gravity of 19.32, so if you took a cubic meter of gold, it would weigh 19.32 times as much as a cubic meter of water.

Metal Density Chart

The chart below describes the various specific gravities of architectural metals, which range from the lightness of titanium and aluminum to the heavy density of lead and gold metals. Magnesium and silver, though not necessarily architectural metals, are indicated for relational comparison.

Metal Density Chart: Showing density and correlating specific gravity.
Metal Density Chart: Showing density and correlating specific gravity.

Another way to understand specific gravity is how it relates to other materials. Plastics have a very low specific gravity, hovering around 0.9 to 1.5. When you pick up a piece of plastic it feels light and has a cheapness to it. Plastic materials can be formed and painted to look like metal, but they will always feel hollow. What you're feeling is the material's density, its specific gravity. 

With the exception of aluminum, most architectural metals are very dense. They have a very high specific gravity. Metals typically have a dense crystal structure. The atoms which make up the material are aligned in a very dense pattern. You can feel that sense of density to the touch. If you tap the material, you can hear the metal resonate. This is because of its dense and hard atomic structure. This is what makes metal sound like metal.