Why do some chocolate bars have a lightly colored, powdery film on their surface?

This light, powdery film is called bloom. When chocolate is exposed to temperatures above 75°F, the cocoa butter can change from solid to liquid and move toward the surface of the bar. Subsequent cooling will result in cocoa butter crystals forming a thin, lightly colored, powdery film on the surface of the bar. It also leaves some cocoa particles uncoated inside the bar, causing the chocolate to taste dry, chalky, and grainy. Obviously, higher temperatures can cause a bar to melt and deform, but even at temperatures around 80°F a bar may not deform, but may develop bloom. Chocolove should be kept out of direct sunlight and stored between 50°F and 70°F. Chocolove is in excellent condition when it is shipped from our warehouses. We go to great lengths to ensure that our storage conditions are ideal and that the transportation used to carry our chocolate is appropriate and refrigerated. Once it leaves our facility we endeavor to educate and monitor our distributors to assure there is ...  more