How do you test liquid or solid samples with your [DIY Spectrometer](/wiki/spectrometer)?

###Sample containers

A good sample container has flat sides, so you can shine lights (and lasers) through it without lots of reflections. It's also good to have the light travel through a consistent amount of the sample -- many cuvettes (traditional spectrometry sample containers) are 1cm x 1cm, so the light always goes through 1cm of the sample.

[![dropper.jpg](https://i.publiclab.org/system/images/photos/000/001/730/medium/dropper.jpg)](https://i.publiclab.org/system/images/photos/000/001/730/original/dropper.jpg) [![Cuvette_with_penny.jpg](https://i.publiclab.org/system/images/photos/000/001/731/medium/Cuvette_with_penny.jpg)](https://i.publiclab.org/system/images/photos/000/001/731/original/Cuvette_with_penny.jpg)

_A square-sided bottle, left, and a cuvette, right (photo from [Wikipedia](http://simple.wikipedia.org/wiki/Cuvette)._

###Water samples

Water is usually very clear in small amounts -- even murky water in a small container will look pretty transparent. That makes it hard to measure with spectrometry unless you shine light through a *lot* of it. But some tests have been done -- see this example of a scan of water from the Charles River before and after 7 days of settling, by [Jeff Hecht](https://spectralworkbench.org/sets/show/330):

[[![charles-river.png](https://i.publiclab.org/system/images/photos/000/001/732/medium/charles-river.png)](https://i.publiclab.org/system/images/photos/000/001/732/original/charles-river.png)](https://spectralworkbench.org/sets/show/330)

However, most research in Public Lab to date has focused on oil spectroscopy -- attempting to identify petroleum residue in sediments. Read on to learn more!

###Oil samples

more soon...