Calcium Crystals vs. Scale
NOTE: This article has been revised from its original version, due to learning more from laboratory results. We still have more unanswered questions about crystals than we have answers. Why do they harden? How many forms are there (we know of at least 3)? Why are some crystals easy to clean up, and others stubborn? What common denominators are involved, beyond cold water and lack of calcium hardness?