The OES is our only optical instrument. It is also the “workhorse” for environmental analyses that do not demand the highest sensitivity. The OES detects the intensity of light emitted when elements of interest are excited in the plasma; a fundamentally different analysis compared to the other mass spectrometers run in the lab. Because of this, and the inherently robust nature of the instrument, the OES allowers Keck Collaboratory users a straightforward means for analyses of major and minor elements in a myriad of environmental samples, with relatively high through-put. The OES has been used extensively in applications ranging from earth science to toxicology to zymurgy.