Akoya pearl bleaching is a common, but generally undisclosed treatment used to even out the color in white cultured pearls. After the harvest, pearls are soaked and heated in a mild pearl cleaning solution under bright fluorescent lights. The result is a more even white color over all the pearls. It is common practice to color enhance or dye the pearls after the bleaching process to add a subtle overtone. Dyeing takes place after the pearls are drilled and is sometimes detectable by examining the drill hole under magnification. Polishing and sometimes coating complete the process. Pearl producers claim that the process is necessary in order to create the matched strands of pearls that the market demands and do it economically.