Most crystals are anisotropic and birefringent , which means they will cause interference between doubly refracted light rays passing through. Both constructive and destructive interference occurring at the microscope analyzer will cause the formation of beautiful patterns that can be captured as digital images by the QX3 microscope. Many chemicals available at local drug stores and supermarkets can also be effective specimens under polarized illumination. These chemicals include vitamins, moth balls and crystals, aspirin and other painkillers, pharmaceuticals, darkroom chemicals, sugars, and some dairy products. Occasionally, chemicals decompose upon heating and will be poor subjects for examination under the microscope.
Salts are notoriously bad candidates for the melt-recrystallization process.
Another very effective method of preparing recrystallized chemicals for observation with polarized light microscopy is to allow soluble chemicals to slowly form crystallites while undergoing radical concentration increases during solvent evaporation. This method is especially useful when trying to prepare salts for examination under crossed polarized illumination. Often, chemicals can be made to dissolve much more quickly by applying some heat to the solvent, either through the use of a hot plate or stove. The solution containing dissolved chemicals will flow underneath the coverslip and fill the entire volume between the coverslip and microscope slide. If too much solution is placed on the slide, then excess solution will gather at the edges of the coverslip.