The Clarity Enhancement Process: 

During the clarity enhancement process we insert a microscopic amount of material into the imperfection. This material has the same optical refraction index as the diamond. When light travels from one medium to another, it either changes its course or reflects in a different direction. When light attempts to pass through a non-enhanced diamond that has a feather, the light hits the feather and reflects in a number of directions. That is why we see the feather, and the diamond doesn't appear to be clean. With a Clarity Enhanced diamond, the light passes through the natural feather because the material used for the enhancement has the same optical characteristics as the diamond. This makes the enhanced imperfections invisible.