Candling Eggs: A Simple How-To Guide
Candling shines a bright light through an egg to see inside. Learn when to candle incubating eggs, how to read development, and how to spot a non-developing egg.
Candling is shining a bright light through an egg in a dark room to see inside without breaking the shell, used to check whether incubated eggs are developing or to inspect eating eggs for quality. Candle incubated eggs around day 7 to 10 to look for the spider web of veins that signals a living embryo, and again around day 14 to 18 to confirm growth. The technique is simple, takes seconds, and lets you remove non-developing eggs before they spoil. Here is exactly how to do it.
Egg Candling Tools
Magicfly Rechargeable Egg Candler Tester
Bright cool LED candler for monitoring egg development without overheating.
NestEcho Egg Candler Light Tester Lamp
Focused candling lamp that helps reveal veins in brown and blue eggs.
What candling shows you
The name comes from the old practice of holding an egg up to a candle flame. The bright light passes through the porous shell and lights up the contents, revealing what is happening inside. For hatching eggs, candling tells you whether an embryo is developing. For eating eggs, it reveals cracks, blood and meat spots, and the size of the air cell, which indicates freshness. A dedicated LED egg candler gives the best results because its beam is bright, focused, and cool enough not to harm a developing egg.
How to candle, step by step
- Darken the room. Candling only works in full darkness. Turn off the lights or work at night.
- Wash and dry your hands. Clean, dry hands protect the egg's bloom and keep bacteria off the shell.
- Hold the light to the rounded end. The air cell sits at the wide, rounded end. Press the candler gently against it and tip the egg slightly.
- Look quickly. Note what you see, then return the egg to the incubator within a minute or two so it does not cool.
- Mark and track. A soft pencil mark lets you track each egg between candling sessions.
When to candle incubating eggs
Timing matters. Candle at the right points and avoid the ones that risk the chick.
| Incubation day | What to do |
|---|---|
| Days 1 to 3 | Do not candle. There is little to see and eggs are best left undisturbed. |
| Days 7 to 10 | First candling. Look for veins and a dark embryo spot. Remove clears and blood rings. |
| Days 14 to 18 | Second candling. Confirm a large dark mass and growing air cell. |
| Last 3 days (lockdown) | Stop candling. Leave eggs alone so chicks can position to hatch. |
Reading what you see
A developing egg
Around day 7 to 10 a healthy fertile egg shows a network of red blood vessels radiating from a dark central spot, the embryo. As days pass, the dark mass grows larger and the air cell at the rounded end expands. By late incubation the egg looks mostly dark and solid with a clear air cell on top, and you may even glimpse the chick moving.
A clear egg
If an egg stays bright and empty after day 7 to 10, it was likely infertile or never began developing. Candle it again a day or two later to be sure, then remove it.
A blood ring
A single red ring or circle around the inside of the shell means an embryo started but died early. These should come out of the incubator.
Removing non-developing eggs is important. A dead or rotting egg can leak or even burst, spreading bacteria to the healthy eggs around it.
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Candling eating eggs
Candling is not just for hatching. Hold an eating egg to the candler in a dark room and you can spot:
- Internal cracks that are invisible on the surface.
- Blood spots and meat spots, which are harmless but some people prefer to remove.
- Air cell size. A small air cell means a fresh egg; a large one means an older egg.
Commercial egg graders candle every egg this way. For everyday backyard eggs the float test usually tells you what you need about freshness, but candling is useful before selling eggs or before choosing which ones to set in an incubator.
Tips for tricky eggshells
Light-colored shells candle easily, but dark brown eggs like Marans and blue or green eggs are much harder to see through. For these, use the brightest candler you have, press it firmly against the shell, and work in complete darkness. Even then, you may not see as much detail, so rely more on the float and weight of the egg and on a second candling session a few days later. Be patient, keep sessions short, and you will quickly get a feel for reading your own eggs.
Frequently Asked Questions
What is candling an egg?
Candling is shining a bright light through an egg in a dark room to see inside the shell without opening it. The name comes from the old practice of holding eggs up to a candle. Today keepers use a small LED egg candler. Candling reveals whether an incubated egg is developing, shows the growing air cell and veins, and can spot cracks, blood spots, or a clear, undeveloped egg.
When should I candle incubating eggs?
Candle incubated eggs around day 7 to 10 to check for development, and again around day 14 to 18 to confirm growth before hatch. At day 7 to 10 you should see a network of veins and a dark spot, the embryo. Avoid candling in the first few days, when there is little to see, and stop candling in the last few days before hatch so you do not chill the eggs or disturb the chick's positioning.
What does a fertile developing egg look like when candled?
A developing egg shows a spider web of red blood vessels spreading from a dark central spot, which is the embryo. As incubation progresses the dark mass grows and the air cell at the rounded end enlarges. By late incubation most of the egg looks dark and solid with the air cell on top. Movement of the embryo may be visible. These are the signs of a healthy, developing fertile egg.
How can I tell if an incubated egg is not developing?
A clear egg that stays bright and empty when candled after day 7 to 10 was likely infertile or never started. An egg with a blood ring, a single red circle around the inside of the shell, means the embryo started but died early. Both should be removed from the incubator, since a non-developing egg can rot and even explode, contaminating the others. When in doubt, candle again in a day or two before removing.
Can you candle eggs you plan to eat?
Yes, candling is also used to check eating eggs for quality. Hold the egg to a candler in a dark room to spot internal cracks, blood spots, meat spots, or a large air cell that indicates an older egg. Commercial egg graders candle this way. For backyard eggs the float test is usually enough for freshness, but candling is handy for inspecting eggs before selling or before setting them in an incubator.
What kind of light do I need to candle eggs?
A dedicated LED egg candler works best because it gives a bright, focused, cool beam that will not overheat the egg. A strong small flashlight can work in a pinch, especially for lighter-colored shells. Dark brown and blue eggs are much harder to candle and need a very bright light. Always candle in a fully darkened room and hold the light against the rounded end of the egg for the clearest view.
Does candling hurt the developing chick?
Brief, careful candling does not hurt the embryo. The key is to be quick and gentle so the egg does not cool too much or get jostled. Handle eggs with clean, dry hands, keep them out of the incubator only a minute or two, and return them promptly to maintain temperature and humidity. Avoid candling during the final days before hatch, when disturbing the egg can interfere with the chick getting into position.
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