Cross polarization micro-photographs of Epson Salt crystals. The purple/pink backgrounds in these images are the result of adjusting the orientations of the polarizers and inserting a full wave retarder. The colors in these images are not computer generated, they are the result of how the polarized light passes through crystals of different thicknesses.
(Click on any image to view it full size.)
Alum (potassium aluminum sulfate) is a cooking additive. I prepared my crystal samples by dissolving Alum power in water until the solution reached saturation, then placing a few drops on a microscope slide and allowing to air dry. Sometimes I use a coverslip to force the crystals to form in thinner layers. Alum seems to begin crystal formation pretty quickly, within an hour you can see crystals on the surface of the solution. You can even watch the crystals grow in real time while observing under the microscope.
Images in this post were taken using a student grade lab microscope with an attached 5mp camera.
