At about day 14, the eggs do start getting very dark and more difficult to see, especially if they are small eggs. If you have a movie or slide projector, they are great to hold the egg over while cupped between your thumb and point finger(point projector at ceiling). That's what I've been using, but it helps a great deal to turn off all lights and do it in a dark room....., can really make the difference, even w/flashlight and box over bulb method.