The Complete Guide to Chicken Egg Candling: Day-by-Day Charts, When to Start, and Identifying Good vs. Bad Eggs

Peering into an egg may seem like a small act, but it opens a window into an astonishing world of life in the making. Candling lets you watch the quiet miracle of a chick forming inside its shell, spotting the first flicker of movement and the intricate web of veins that signal healthy development.

Whether you’re a seasoned poultry keeper or a curious beginner, this guide will walk you through every step—from when to start candling to spotting which eggs are thriving and which need to be removed so you can confidently track your flock’s progress day by day.

Candling Fundamentals (The How-To)

Why Candling is Essential

1. Remove Non-Viable or Infertile Eggs: Not all eggs will develop into chicks. By identifying and removing infertile or early-death eggs, you prevent the risk of spoilage and contamination that could threaten healthy eggs in the incubator.
2. Monitor Embryonic Growth and Health: Candling allows you to track the development of the embryo, from the formation of blood vessels to visible movement as the chick grows. This helps you identify potential problems early, giving you the chance to adjust incubation conditions if needed.
3. Check for Cracks and Shell Integrity: Even a small hairline crack can allow bacteria to enter and compromise the egg. Candling makes it easier to spot damaged eggs before incubation progresses too far.

The Candling Setup: Tools and Technique

Using a Dedicated Egg Candler vs. a Flashlight

While a professional egg candler provides the most consistent and focused illumination, you can also successfully candle eggs using a high-lumen LED flashlight. When using a flashlight, choose one with a narrow beam and high brightness to penetrate the shell effectively.

The Importance of a Dark Room

For best results, always candle eggs in a darkened space. Any ambient light can make it difficult to see the developing embryo or fine blood vessels clearly. Closing blinds, turning off overhead lights, or even using a small closet can make a big difference.

How to Hold the Egg Correctly

• Position the egg with the large end up to get a better view of the air sac and embryo.
• Gently rotate the egg to examine different angles, as the embryo may be positioned to one side.
• Avoid shaking or jostling the egg, especially during the early days when blood vessels are delicate.

By following these basic candling fundamentals, you can confidently monitor your eggs, protect developing embryos, and improve your overall hatch success.

When to Candle Eggs: Incubation vs. Edibility

Candling for Hatching Success (Incubation)

Proper candling during incubation allows you to track embryo growth, remove non-viable eggs, and adjust incubator conditions as needed. Timing is critical to avoid disturbing fragile embryos while still gathering useful information.

The First Candle (Critical Timing)

• Optimal Timing: Day 3–4 for white eggs; Day 4–5 for brown eggs.
• Why Not Earlier: Candling on days 1–2 is generally ineffective because the embryo is too small and nearly invisible. Early candling can also risk disturbing the yolk or fragile embryonic tissue.
• What to Look For: A small dark spot with radiating blood vessels—these are the early signs of life. A clear egg at this stage usually indicates infertility or early embryo death.

The Second Check (Mid-Incubation)

• Timing: Day 7–10 of incubation.
• Purpose: Confirm continued embryo development and remove eggs that have stopped growing.
• Indicators of Healthy Embryos: Visible blood vessels spreading throughout the egg, a slightly darker interior, and sometimes subtle movement. Eggs showing blood rings or remaining clear should be discarded.

The Final Check (Pre-Lockdown)

• Timing: Day 14–18.
• Purpose: Assess late-stage development before lockdown (when turning stops and humidity is increased for hatching).
• What to Observe: The embryo should fill most of the egg, movement may be noticeable, and the air cell will have grown to its pre-hatch size. Removing any non-developing or cracked eggs at this stage prevents contamination and ensures optimal hatching conditions.

Candling Eggs for Eating/Freshness

Candling is equally useful for evaluating eggs intended for consumption, helping determine age, freshness, and internal quality.

Air Cell Size

• The air cell forms at the larger end of the egg and grows as the egg ages due to moisture loss.
• A small, firm air cell indicates a very fresh egg, while a large air cell suggests the egg is older. This is the primary indicator of age for edible eggs.

Internal Quality

• Use candling to detect internal defects such as cracks, blood spots, or meat spots.
• Eggs that are clear, with a small air cell and no visible defects, are ideal for consumption.
• Avoid eggs with significant internal anomalies or unusually large air cells, as these may indicate compromised quality.

By understanding when to candle eggs first time for both incubation and eating, you can maximize hatch rates or ensure you’re selecting the freshest eggs for your kitchen. Proper timing and careful observation are key to making candling an effective part of your egg management routine.

Day-by-Day Development Chart and Checklist

This chart provides a clear, day-by-day guide to monitoring embryo development via candling, ensuring healthy growth and a successful hatch.

1 Early Stage: Formation of Life (Days 1–7)

Day	Developmental Signs	Candling Observations	Tips / Actions
Day 3–4	Embryo begins forming; tiny heart may start beating.	Small dark spot visible; faint red blood vessels radiating outward.	First candling check; avoid jostling eggs; confirm embryo presence. White eggs are easier to see than brown.
Day 7	Rapid growth of embryo; blood vessel network becomes prominent. Air cell forming.	Dark spot larger; clear, defined blood vessels; slight movement may be visible.	Record progress on incubation chart; remove any eggs with blood rings or clear interior. Ensure proper temperature and humidity.

2 Mid-Incubation: Growth and Movement (Days 8–14)

Day	Developmental Signs	Candling Observations	Tips / Actions
Day 10	Embryo increasing in size; movement more noticeable; feathers beginning to form internally.	Veins prominent; embryo occupies more of the egg; movement may be observed.	Adjust humidity if air cell size is off; continue monitoring temperature and rotation. Remove non-viable eggs.
Day 14	Chick nearly fills the egg; blood vessels well established; yolk being absorbed.	Egg appears darker; less light passing through; movement noticeable.	Prepare for pre-hatch period; confirm all eggs are viable; stop unnecessary handling of fragile eggs.

3 Late Stage: Pre-Hatch Darkness (Days 15–21)

Day	Developmental Signs	Candling Observations	Tips / Actions
Day 18	Chick fully occupies the egg; internal rotation stops; preparing for hatching.	Egg mostly dark; movement may be limited; air cell fully formed at large end.	Enter “lockdown”: stop turning eggs, increase humidity to ~65–70%, maintain temperature at 100.5°F.
Day 20 (Pipping Stage)	Chick begins breaking into air cell; external pip may start.	Dark egg with small cracks; internal pip visible; slight movement and peeping sounds.	Monitor quietly; do not assist hatch unless absolutely necessary; maintain high humidity to prevent shell sticking.

Quick Candling Checklist for All Stages

• Clear egg → Remove (infertile or embryo died)
• Blood ring → Remove (embryo died early)
• Visible blood vessels / dark spot / movement → Healthy → Keep in incubator
• Air cell size → Adjust humidity:
  • Large air cell → Increase humidity
  • Small air cell → Decrease humidity
• Egg shell issues (cracks, leaks) → Remove to prevent contamination

This Day-by-Day Candling Chart simplifies the process of monitoring chicken egg development while maintaining proper incubation practices. It ensures you know exactly what to look for at each stage, helping maximize hatch success.

Identifying Non-Viable Eggs (The Bad Egg Candling Chart)

1. Infertile Eggs (Clear Eggs)

Appearance:

• The egg looks mostly clear, sometimes with only a faint shadow of the yolk.
• No blood vessels or embryo are visible.
• Occasionally, you might notice a tiny white dot on the yolk, called the germinal spot or “bullseye”—this is normal in unfertilized eggs.

Timing: Usually visible by Day 5–7 of incubation.

Action: Remove immediately; these eggs will not develop and can spoil, affecting nearby viable eggs.

2. Dead Embryos (Stops)

Signs to Watch:

• Blood Ring: A thin, solid ring of blood around the inside of the egg, often separated from the embryo. Indicates the embryo started developing but died early.
• Stop-and-Float / Quitters: A dark mass inside that remains motionless, sometimes in cloudy or murky egg whites. The contents may swirl when you gently rotate the egg but show no life.

Timing: Typically Day 7–14, though early deaths can occur within the first few days.

Action: Remove immediately to prevent contamination of healthy eggs.

3. Rotten or Contaminated Eggs (Rots)

Appearance:

• Cloudy or murky contents, sometimes with black spots or streaks.
• Air cell may be abnormal in size or color.
• Sometimes looks like a “snow globe” effect when rotated.

Extra Clue: Rotten eggs usually emit a strong sulfur smell once removed from the incubator.

Action: Remove immediately. Rotten eggs can explode and spread bacteria to surrounding eggs.

Quick Reference Table

Egg Type	Appearance Inside	Timing	Key Signs	Action
Infertile / Clear	Transparent, yolk shadow only	Day 5–7+	No veins, only germinal spot	Remove
Dead Embryo (Stop)	Blood ring, dark mass, cloudy/sloshy	Day 7–14	No movement, embryo stopped	Remove
Rotten / Contaminated (Rot)	Cloudy, murky, black streaks, abnormal air sac	Any stage	Smells bad, high blowout risk	Remove

Pro Tips:

• Candle in a completely dark room for the clearest view.
• Handle eggs gently; live embryos show veins and sometimes movement by Day 7–10.
• Dark-shelled eggs require a brighter light and careful angling to see inside.
• Keep an incubation log to track which eggs are viable and when they were removed.

Regular egg candling lets you track embryo development, spot infertile or dead eggs, and prevent contamination. Knowing what to look for ensures healthier hatches and helps you adjust incubation conditions for better results.