If I understand the question correctly, when the bevel is fully set and you look at it under a bright light, gently rolling the apex back and forth, there should be no white line one sparkles showing. It should reflect the shine from the side of the bevel and then nothing at the apex and then the shine of the bevel. A loupe is actually a better source for information from my experience. You can get a 60X lighted loupe for very little money.