A spectrometer may not sound like what you wanted for your birthday, but it's a ubiquitous tool for scientists to identify unknown materials, like oil spill residue or coal tar in urban waterways. But they cost thousands of dollars and are hard to use -- so we've designed our own.

 

This open hardware kit costs only $35, but has a range of more than 400-900 nanometers, and a resolution of as high as 3 nm. A spectrometer is essentially a tool to measure the colors absorbed by a material. You can construct this one yourself from a piece of a DVD-R, black paper, a conduit box, and an HD USB webcam.

 

Public Lab community members have used this new tool to identify dyes in "free and clear" laundry detergent, to test grow lamps, and to analyze wines.