The kids and I cracked open one of their Christmas gifts early, a crystal-growing kit. The first thing we noticed was the strong odor that came from the bag of materials, the easily-recognized smell of sulphur. Upon opening it up and reading the instructions, we learned that the smell came from our crystal-growing seed material, potassium aluminum sulfate. And it was supplied in a variety of colors for our crystal-farming enjoyment. Naturally, we had to make the blue crystals first.
Potassium aluminum sulfate, or potassium alum, or potash alum, is the stuff used in deodorant, water treatment, aftershave and other fun industrial applications. What's funny is that it stinks so badly, but ultimately is about the cleaning and de-stinking of the world.
These photos are all observing an area about 3mm across
After our crystals were grown, about a week-and-a-half, I tweezed a few samples of the small crystals out of our experiment cup and shot them using the crossed-polar light technique. This is where I use a polarized filter on my lens that is at a 90° angle to the polarized filter on my flash. You may recall, this technique filters light to reveal some
pretty psychedelic rainbow effects.
These photos were shot from above the crystals as they sat on a stretched piece of plastic wrap, suspended above the inside of a box backed with black construction paper; the flash was under the subject on one side, providing light from beneath the crystals. The use of transmissive light is one of the methods used by Ken Libbrecht to shoot snowflakes. As for why the black paper looks red in the photos, I can't account for that. Without more experimenting, I can't be sure if it looks like that because of the use of polarized filters, the plastic wrap, the dye used in the black paper (a reddish black dye vs a greenish black?), or a combination of these factors.
The color in these photos comes from several sources: The crystals were infused with some sort of blue/purple food coloring, and you can see some blobs of the coloring encased inside these crystals. Also, the cross-polarized light creates little flecks of rainbow colors inside these tiny prisms. Every mineral will bend cross-polarized light in a different way, and geologists, chemists, and other scientists use this technique to observe the presence and characteristics of different minerals and compounds in their study.
And yes, you can see the obvious dust on my sensor in these pics. Sorry about my dirty camera.
The girls and I are currently growing sugar crystals, so we can eat our experiment afterward. I'll be sure to shoot them, but if you're impatient and want to see sugar up close now, take a look at
some of my past posts.
