A key step in assuring the quality of investment castings is making sure that the metal has the exact composition that is specified and required to deliver the desired properties. An optical spectrometer, also referred to as a spectrophotometer, spectrograph or spectroscope, is an invaluable instrument for measuring metal composition. Before casting all of the parts in a run, a test specimen is poured and analyzed to determine its chemistry. This is done by vaporizing a very small amount of the metal and analyzing the gas in the optical spectrometer. It can identify the elements present by measuring the wave lengths of the light that is present. A display or print out tells the operator the percentages of each alloy component, which can then be adjusted, if necessary.