Thought I would share how I candle eggs. After my eggs have been in the incubator about 10 days or so I candle them. You could do it before but It is hard for me to decide weather something is in them or not at about 10 days there is no mistake. All you need is a flashlight, roll of toilet paper, a dark room and an egg.
Hold the flashlight between your knees put the roll of toilet paper on the light and the egg on it. That's all there is to it. If the egg is clear like this one nothing is in it, but if your egg has a dark blob in it, it has a chicken in it. The roll of toilet paper funnels the light and the opening in the roll is just the right size for the chicken egg. A dark room helps but the toilet paper roll reflects the flash so I had to take this picture during the day