2013-11-02 by wsdchemical(A ) means: In order to obtain a higher grade of whiteness, the bleaching must be carried out on the basis of whitening. Whitening there are two concepts ( 1 ) on the blue whitening : absorb yellow light , remove the fabric khaki Ze . ( 2 ) Fluorescent whitening : the invisible ultraviolet into visible light blue or purple reflected , to increase the reflectance of the fabric . After whitening treated fabric , very white, crystal, translucent , can exceed conventional whiteness - magnesium oxide standard ( two ) whitening machine principle 1 , the color is due to some light reflected from an object , the role of human senses and apparent , no light source , there will be no color. If an object absorbs visible light waves of a certain portion of the other light waves reflected sunlight , then show the color , if all seven kinds of light reflection , is rendered white , and vice versa for Black 2 , fluorescent brighteners can not only reflect daylight seven kinds of visible light waves become white , but also the UV reflection of blue fluorescent brightener , with complementary yellow reflective fabric , increasing the reflection of visible light , producing translucent crystal white. In the absence of UV monochromatic light , the whitening effect is inferior to the sun. FWA properties similar to disperse dye or direct dye, but with the general nature of different dyes : ① fluorescent brightener at low dosage , the color yield proportional to the amount added depth and dge ; but the amount is increased to a certain value , not only lost whitening effect , but also becomes dark yellow ② general dge darker , more able to cover the defect ; fluorescent whitening effect , but better, more obvious defects ③ fluorescent brighteners and aqueous solutions of their own in the sunlight brightening effect is not obvious , only infected fibre have strong whitening effect .