This is due to sprue placement and the flow of the crystals. The LS2 crystals are long and thin and when they flow they line up like logs going down river to the log mill. So when we try to cheat and save that nice incisal edge we waxed and move the sprue down the axial wall (usually facial) the crystals flow into the mold and have to turn to go down the long axis of the tooth. The last crystals that enter the crown don't have a chance to turn, so when we remove the sprue we are looking at the short, polished, end of the crystal and they act as fiber optic cables and transmit the light right through the crown and don't reflect it back. This results in the "BullsEye," a low value spot with a high value ring around it.
To fix this, move your sprue back to the proper position aimed straight down the prep on the incisal edge or cusp tip. This will prevent this from happening.
