How to Test if an Egg is Good: The Kitchen Detective's Manual for Fresh Eggs

I've been cracking eggs since I was tall enough to reach the counter on a stepstool, and let me tell you, there's nothing quite like the disappointment of breaking a bad egg into your Sunday morning pancake batter. That sulfurous stench, that greenish tinge—it's enough to put you off breakfast entirely. Over the years, I've become something of an egg detective, and I'm about to share every trick I know.

The truth about eggs is that they're remarkably good at keeping secrets. Unlike a bruised apple or moldy bread, a spoiled egg can look perfectly innocent from the outside. But eggs, being the clever little packages they are, actually give us plenty of clues about their freshness—you just need to know what to look for.

The Water Float Test: Your First Line of Defense

Fill a deep bowl with cold water. Gently lower your egg into it. What happens next tells you almost everything you need to know. A fresh egg sinks and lies flat on its side at the bottom. An egg that's a week or two old might tilt upward slightly, with the larger end rising. But if that egg stands upright or—heaven forbid—floats to the surface, you're dealing with an old-timer.

Why does this work? It's all about air. As an egg ages, moisture evaporates through its porous shell, and air seeps in to fill the void. The air pocket inside grows larger over time, creating buoyancy. I remember my grandmother explaining this to me while we tested eggs from her henhouse, and it felt like learning a magic trick.

Now, here's what most people get wrong: a floating egg isn't necessarily rotten. It's just old. You might still be able to use it for hard-boiling (older eggs actually peel easier), but I wouldn't trust it for a delicate soufflé or fresh mayonnaise.

The Candling Method: Seeing Through the Shell

Before electricity blessed our kitchens, people held eggs up to candle flames to check their quality—hence the term "candling." Today, you can use a flashlight in a dark room. Hold the egg up to the light, large end up, and look for shadows or dark spots inside.

A fresh egg shows a small air cell and a barely visible yolk. As eggs age, that air cell grows, and you might see the yolk moving around more freely. Dark spots or cloudy areas? Those could indicate bacterial growth. I once candled an egg that looked like a tiny storm system was brewing inside—needless to say, it went straight to the compost.

The Shake Test: Quick but Not Foolproof

Hold the egg close to your ear and give it a gentle shake. Fresh eggs are silent because the contents fill the shell completely. Older eggs slosh. The white becomes thinner and more watery over time, allowing the yolk to move around.

I'll be honest though—this method makes me nervous. I've seen too many people get overzealous with their shaking and end up with egg on their faces (literally). Plus, it's not the most reliable test. Some perfectly good eggs might make a slight sound, especially if they've been jostled during transport.

The Crack and Examine Method: The Final Verdict

Sometimes you just have to crack the egg open to know for sure. This is where your senses become your best tools. A fresh egg has a firm, rounded yolk that sits high, surrounded by thick white that stays close to the yolk. There's also a thinner, more watery white that spreads out a bit.

As eggs age, everything flattens out. The yolk breaks more easily, and the white becomes uniformly runny. But age isn't the enemy here—spoilage is. Trust your nose above all else. Fresh eggs have almost no smell. A slight eggy aroma is normal, but anything sulfurous, sour, or just plain wrong means that egg has crossed over to the dark side.

The visual cues of spoilage are equally unmistakable. Green or pink tinges in the white, black or green spots, or any unusual coloration means bacteria have set up shop. I once cracked an egg that looked like abstract art—beautiful in its way, but definitely not breakfast material.

The Shell Inspection: First Impressions Matter

Before you even get to testing, examine the shell carefully. Cracks are obvious entry points for bacteria. But also look for unusual textures, powdery coatings, or slimy spots. A healthy eggshell should feel slightly rough and chalky, not smooth or greasy.

Here's something most people don't know: those tiny bumps and calcium deposits on shells? They're actually signs of freshness in farm eggs. Commercial eggs are washed and sometimes coated with mineral oil, which removes these natural variations but also strips away the egg's protective bloom.

Storage Wisdom: An Ounce of Prevention

The way you store eggs dramatically affects how long they stay good. In America, we refrigerate our eggs because commercial processing removes the natural protective coating. In many European countries, eggs sit on regular shelves because they keep that coating intact.

Always store eggs in their original carton, not those cute egg holders built into refrigerator doors. The carton prevents the eggs from absorbing odors (eggs are surprisingly good at picking up flavors from neighboring foods) and helps maintain consistent humidity. Plus, you can check the sell-by date whenever doubt creeps in.

Here's my personal rule: eggs in the main body of the fridge stay fresh for 3-5 weeks past the sell-by date. Eggs stored in the door? Cut that time in half. The temperature fluctuations from opening and closing the door age eggs faster than you'd think.

The Science of Spoilage: What's Really Happening

Understanding why eggs go bad helps you make better judgments about their safety. Eggs spoil through two main routes: bacterial contamination and natural degradation. Salmonella gets all the press, but it's actually relatively rare in properly handled eggs. More common is simple age-related breakdown of proteins and the gradual invasion of airborne bacteria through the porous shell.

The protective systems in an egg are remarkable. The shell might look solid, but it has thousands of tiny pores. Fresh eggs have natural defenses—antimicrobial proteins in the white, membranes that resist bacterial penetration, and that protective bloom I mentioned. But time weakens all these defenses.

Temperature abuse accelerates everything. An egg left on the counter for two hours ages as much as one kept refrigerated for a week. This is why that carton of eggs you forgot in the car after grocery shopping needs extra scrutiny.

Special Cases and Exceptions

Not all egg oddities indicate spoilage. Blood spots on the yolk? Perfectly safe—just a broken blood vessel during formation. Cloudy whites? Actually a sign of extreme freshness, caused by dissolved carbon dioxide that hasn't had time to escape. Green ring around a hard-boiled yolk? Overcooked, not spoiled.

But then there are the genuine warning signs. Eggs that feel unusually light for their size. Shells that seem thin or brittle. Any egg that's been left out overnight in summer heat. When in doubt, throw it out—no omelet is worth food poisoning.

The Bottom Line on Egg Testing

After decades of cooking, I've learned that fresh eggs are forgiving. They'll tell you when they're past their prime if you know how to listen. The float test catches most problems before you crack the shell. Your nose catches anything the float test misses. And common sense fills in the gaps.

I still remember the first time I confidently declared an egg bad based on the float test alone. My mother made me crack it anyway, "for the learning," she said. Sure enough, it reeked. That lesson in trusting the process has served me well ever since.

The real secret to egg safety isn't complicated: buy from reputable sources, store properly, use within a reasonable time, and trust your senses. Every test I've described is just a tool to help your natural instincts. Because at the end of the day, humans have been successfully identifying bad eggs long before anyone thought to write down the methods.

Authoritative Sources:

United States Department of Agriculture. Shell Eggs from Farm to Table. USDA Food Safety and Inspection Service, 2019.

McGee, Harold. On Food and Cooking: The Science and Lore of the Kitchen. Scribner, 2004.

Stadelman, William J., and Owen J. Cotterill, editors. Egg Science and Technology. 4th ed., Food Products Press, 1995.

Centers for Disease Control and Prevention. Salmonella and Eggs. CDC.gov, 2022.

Ricke, Steven C., et al. Eggs and Egg Products as Functional Foods and Nutraceuticals. John Wiley & Sons, 2019.