How to Test Egg Freshness Using Water: What Science Says and How to Do It Safely

Ensuring the freshness of eggs is essential not only for better taste and texture, but also for food safety. While expiration dates on cartons provide a general guideline, eggs can remain edible long after the printed date if stored properly. One of the simplest, most reliable, and widely recommended methods for checking egg freshness is the water test, sometimes called the float test. This technique has been used for generations and is supported by food safety experts because it relies on predictable physical changes that happen inside an egg as it ages.

Why the Water Test Works

When an egg is freshly laid, it contains very little air inside the shell. Over time, however, moisture and carbon dioxide slowly escape through the porous shell, and an air pocket begins to form. The larger this air cell becomes, the more buoyant the egg becomes. This natural process explains why an egg’s behavior in water is a strong indicator of its age.

According to the U.S. Department of Agriculture (USDA), eggs stored in a refrigerator can remain safe to eat for several weeks, but their quality gradually declines as the air cell expands. The water test helps visualize this change without cracking the egg open.

How to Perform the Water Test

To check the freshness of an egg, simply fill a glass, bowl, or jar with enough water to fully submerge the egg. Then gently place the egg into the water and observe how it behaves:

1. Fresh and Safe to Eat — Egg Sinks and Lies Flat

If the egg sinks quickly and rests on the bottom in a horizontal position, it is very fresh. At this stage, the air cell inside is still small, and the egg is likely to have a firm yolk and viscous egg white. These qualities make it ideal for dishes where texture and freshness matter, such as frying, poaching, or soft-boiling.

2. Still Safe but Not Very Fresh — Egg Sinks but Stands Upright

When an egg sinks but tilts upward or stands on its end, the air pocket has grown noticeably. While the egg is still generally safe to eat, its quality has declined. Its whites may be thinner, and the yolk may appear less rounded. These eggs work well for baking, hard-boiling, or any recipe where the structural integrity of the egg is less important.

The Food and Drug Administration (FDA) notes that aging alone does not make an egg unsafe; rather, contamination risks depend on storage conditions and shell integrity. So an upright egg is still usable, as long as it has been properly refrigerated and shows no signs of spoilage.

3. Too Old to Eat — Egg Floats

If the egg floats to the top of the water, it indicates a very large air pocket, suggesting the egg is old and should not be eaten. While floating alone does not confirm bacterial contamination, it strongly suggests that the egg’s internal quality has deteriorated beyond safe consumption. At this point, discarding it is the safest option.

Food science programs such as those from Oregon State University Extension and Penn State Extension consistently recommend discarding floating eggs because both texture and safety may be compromised.

Additional Tips for Egg Safety

• Perform a sniff test after cracking. Even a sinking egg can be spoiled if stored improperly. A sour or sulfur-like odor is a clear sign of bacterial activity.

• Store eggs in the refrigerator. The USDA recommends keeping eggs at or below 4°C (40°F).

• Avoid washing eggs before storage. This can damage the protective cuticle, allowing bacteria to enter more easily.

• Use eggs within 3–5 weeks of purchasing for best quality, though many remain safe beyond that when refrigerated.

Conclusion

The water test is a simple, accessible way to gauge the freshness of eggs without special equipment or experience. By understanding how changes inside the egg affect buoyancy, you can make safer and more informed choices in your kitchen. Paired with proper storage and basic food-safety habits, this method helps ensure that the eggs you use are both high-quality and safe to eat.