Candling eggs
Candling is shining a light through an egg in a dark room to see if a chick is growing. A living embryo is a dark spot with a faint web of blood vessels; an egg the light shines straight through is infertile. Chicken eggs are easy to judge after 8 to 12 days.
How to candle
1.
Work in a dark room with a small, focused flashlight or a candler.
2.
Hold the egg to the light and look at the large end, where the embryo grows.
3.
Be quick and put it back: cooling for less than 10 minutes does not harm the embryo.
4.
White or pale eggs are easier to see into than dark or speckled ones.
What you see
•
Growing: a dark spot in the large end with a faint outline of blood vessels. It gets bigger, until only a dark mass and the air cell show.
•
Clear (infertile): the light shines brightly through, with no blood and no embryo.
•
Stopped growing: a ring or a smear of blood, or a dark spot dried to the inside of the shell.
•
Take out the clear and the dead eggs — they can contaminate the good ones. Ten percent or more of eggs set are infertile.
Which day, for every kind of egg
Candle once the embryo is easy to see, and stop turning for the last 3 days before the hatch (lockdown).
Eggs
Candle
Stop turning
Hatch
Chicken
Day 10
Day 18
Day 21
Muscovy duck
Day 17
Day 32
Day 35–37
Quail (Coturnix)
Day 8
Day 15
Day 17–18
Goose
Day 14
Day 27
Day 30–33
Guinea fowl
Day 13
Day 25
Day 28
Your chicken eggs
Questions
When should you candle chicken eggs?
After 8 to 12 days, when a growing embryo is easy to see.
What does an infertile egg look like when candled?
Clear: it lets the light through brightly and shows no blood and no embryo.
Does candling hurt the embryo?
Not if you are quick: cooling for less than 10 minutes does not harm it.
How long do chicken eggs take to hatch?
21 days. Stop turning them on day 18.
Sources
Last checked September 30, 2026. A common guide — your vet’s plan wins.
More answers
Remembers every animal’s due date and reminds you before each job — the pregnancy check, the pen, the watch. Coming to the App Store this winter.