How to Candle Chicken Eggs: A Beginner’s Step-by-Step Guide

Candling chicken eggs is one of the most useful skills for anyone incubating fertile eggs. It allows you to monitor embryo development, identify infertile eggs, and remove eggs that have stopped developing before they affect the rest of your hatch.

If you’re new to hatching chickens, don’t worry—egg candling is simple once you know what to look for.

In this guide, you’ll learn how to candle chicken eggs, when to do it, what you’ll see at each stage, and common mistakes to avoid.

What Is Egg Candling?

Egg candling is the process of shining a bright light through a fertile egg to observe what is happening inside the shell.

Years ago, people used candles, which is where the name originated. Today, most poultry keepers use a dedicated egg candler or a powerful LED flashlight.

Candling allows you to:

• Check whether an egg is fertile.
• Monitor embryo development.
• Identify infertile eggs.
• Detect eggs that have stopped developing.
• Improve hatch rates by removing non-viable eggs.

Candling does not harm the developing chick when done carefully and for short periods.

Why Should You Candle Eggs?

While it’s possible to incubate eggs without candling, doing so offers several advantages.

Candling helps you:

• Monitor the progress of embryo development.
• Remove infertile eggs before they spoil.
• Detect early embryo loss.
• Reduce the risk of bacterial contamination from rotten eggs.
• Gain valuable experience for future hatches.

It also gives you peace of mind by confirming that your incubator is supporting healthy development.

What Equipment Do You Need?

You don’t need expensive equipment to candle eggs successfully.

Most people use:

• A purpose-built egg candler
• A bright LED flashlight
• A dark room
• Clean hands

Commercial egg candlers usually provide better visibility, especially for darker eggshells, but a quality flashlight can also work well.

When Should You Candle Chicken Eggs?

Timing is important.

The most common candling schedule is:

Day 7

The first candling checks whether development has started.

At this stage you may see:

• Small embryo
• Spider-like blood vessels
• Dark spot inside the egg

Infertile eggs usually appear mostly clear.

Day 10–14

A second candling gives a much better view.

You may notice:

• Larger embryo
• More blood vessels
• Increased movement
• Smaller visible air cell

By now, healthy embryos are usually easy to identify.

Day 18

Many poultry keepers perform one final candling before lockdown.

At this stage:

• Most of the egg appears dark.
• The chick occupies much of the shell.
• The air cell is clearly visible.

After day 18, avoid unnecessary handling as the eggs prepare for hatching.

How to Candle Chicken Eggs

Follow these simple steps:

Step 1: Prepare a Dark Room

The darker the room, the easier it is to see inside the egg.

Turn off lights and close curtains before beginning.

Step 2: Wash Your Hands

Clean hands help reduce the chance of introducing bacteria onto the eggshell.

Avoid using lotions or oils beforehand.

Step 3: Turn On the Egg Candler

Place the light against the larger end of the egg, where the air cell is located.

Do not press excessively hard against the shell.

Step 4: Rotate the Egg Slowly

Gently rotate the egg while observing the inside.

Avoid shaking or making sudden movements.

Handle every egg carefully throughout the process.

Step 5: Return the Egg Promptly

Once you’ve finished examining the egg, place it back into the incubator in the correct orientation.

Try to keep eggs outside the incubator only for a short time.

What Does a Fertile Egg Look Like?

A healthy developing egg changes noticeably over time.

Early development often includes:

• Fine blood vessels
• Dark embryo
• Growing shadow

As incubation continues:

• The embryo becomes much larger.
• The inside appears darker.
• Less light passes through the shell.
• The air cell becomes easier to identify.

Movement may also be visible during later stages.

What Does an Infertile Egg Look Like?

Infertile eggs often remain mostly clear when candled.

Common signs include:

• No visible blood vessels
• No dark embryo
• Mostly transparent interior

If an egg has shown no development after the appropriate amount of incubation time, it is likely infertile.

What Is a Blood Ring?

One of the most common signs of early embryo loss is a blood ring.

Instead of healthy branching blood vessels, you may see a distinct circular red ring inside the egg.

A blood ring generally indicates that embryo development stopped at an early stage.

These eggs should usually be removed from the incubator after confirming there is no ongoing development.

Why Is the Air Cell Important?

The air cell forms naturally at the large end of the egg.

Throughout incubation, it gradually increases in size as moisture leaves the egg.

The developing chick uses this air cell shortly before hatching during internal pipping.

Monitoring the air cell can also provide clues about whether humidity levels have been appropriate during incubation.

Can You Candle Brown Eggs?

Yes.

Brown eggs can absolutely be candled.

However, darker shells allow less light to pass through, making details harder to see compared to white eggs.

Using a high-quality egg candler with a strong LED light often improves visibility.

Common Egg Candling Mistakes

Avoid these common beginner mistakes:

• Candling too frequently.
• Keeping eggs outside the incubator too long.
• Rough handling.
• Rotating eggs aggressively.
• Misinterpreting early development.
• Opening the incubator unnecessarily.

Remember that every embryo develops at its own pace.

If you’re unsure, it’s often better to wait a few more days before making a decision.

Does Candling Hurt the Chick?

No.

Brief and careful candling does not harm the developing embryo.

The key is to:

• Handle eggs gently.
• Minimize exposure outside the incubator.
• Return eggs promptly.
• Avoid excessive handling.

Frequently Asked Questions

What day should you candle chicken eggs?

Most poultry keepers candle around day 7, again between days 10 and 14, and sometimes once more before lockdown on day 18.

Can you candle eggs with a flashlight?

Yes. A bright LED flashlight can work well, although a purpose-built egg candler often provides better visibility.

How long should you candle each egg?

Only long enough to examine development. Keeping eggs outside the incubator for extended periods should be avoided.

Should you candle every day?

No. Frequent handling can unnecessarily disturb incubation. Most successful hatches only require a few candling sessions.

Why can’t I see anything inside my egg?

Possible reasons include:

• The egg is infertile.
• It’s too early in development.
• The shell is very dark.
• The flashlight isn’t bright enough.

Waiting a few more days often provides a clearer view.

Final Thoughts

Learning how to candle chicken eggs is one of the best ways to improve your incubation success. By checking embryo development at the right stages, you can identify fertile eggs, remove non-viable ones, and better understand the hatching process.

With a little practice, candling becomes an easy and valuable part of every hatch, whether you’re incubating a few backyard eggs or managing a larger flock.