Make sure that the room where you do your candling is dark. Place the light against an egg - a viable (live, fertile) egg will show red
veins inside. A dead egg will not show them.
What precoutions are there to take ? First, the light shouldn't be held agains the eggs for too long. A couple seconds is enough for
the examination. Lightbulbs get hot and this heat could damage the embryo. Having a piece of cardboard wrapped around the flashlight will
keep the source away from the egg. Still, you shouldn't expose the eggs to such bright light for too long - this too can affect
the embryo and kill it. Some species are very sensitive to this, for example the chandro family. The last thing would be to always make sure
that the eggs will stay in the same position at all times. They should never be flipped over. The eggs position is easy to maintain when they are
all stuck together in a mass. When having them seperate, it is always a good practice to mark the top of the eggs with a pencil.