How to candle eggs: what to look for on day 7 and day 14

Want the dates for your own animal? Use the chicken egg incubation calculator. It builds a dated schedule in seconds.

Candling means shining a bright light through an egg in a dark room so you can see what is happening inside. It tells you which eggs are developing and which to remove before they go bad in the incubator.

When to candle

For chicken eggs, candle twice:

• Day 7: fertile eggs are easy to spot by now.
• Day 14: you can see which embryos are still growing.

Duck, turkey, guinea fowl and peafowl eggs follow the same pattern. Goose eggs are slower, so candle around day 10 and day 20. Quail eggs have speckled shells that make candling hard; a very bright torch helps.

Stop candling at lockdown, three days before the hatch date. From then on the lid stays closed.

What you need

• A dark room
• A small, bright LED torch or an egg candler
• Clean, dry hands

Work quickly. Each egg should be out of the incubator for only a few seconds, and the whole tray for no more than about ten minutes.

What a fertile egg looks like

On day 7 a fertile chicken egg shows a network of red veins spreading out from a dark spot, which is the embryo. Often you can see the dark eye. If you hold it still, the embryo may twitch.

By day 14 most of the egg is dark. The air cell at the wide end is clear and has grown. You may see movement.

What to remove

• Clear eggs: the light passes straight through with no veins. These were never fertile.
• Blood ring: a red ring around the inside of the shell with no veins. The embryo died early.
• No change at day 14: an egg that looked the same as on day 7 has stopped developing.
• Cracked or leaking eggs, or any egg that smells bad. Bad eggs can burst and spread bacteria.

If you are unsure about an egg, mark it with a pencil and check it again in two or three days rather than throwing it out.

After the last candling

At lockdown, stop turning the eggs, raise the humidity to about 65–70% for chickens and keep the lid shut. The chicks move into position, pip into the air cell and then the shell. Hatching can take 12 to 24 hours after the first pip.

Get your dates

Enter the day you set the eggs in the chicken egg incubation calculator. It gives you both candling dates, lockdown and the hatch window, and shows what is happening inside the egg each day.

Disclaimer: This guide is general information, not veterinary advice. Talk to your vet about your own animals.