im still at college learning acrylic nails and done a friends infills today for practice.When blending down the seam the line would not go invisable and was obvious when i had finished.I used a 150 and 280 grit and buffed for ages.I put a little more acrylic over onto the middle and topof the nail and it didnt look as bad but just wondered why this happened and what i could do to fix it if it ever happened again.