Do Hard Boiled Eggs Float? – What Does It Mean?

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Ever put eggs in a pot of boiling water only to find that they float? If you’re wondering why this happens then the answer may surprise you!

Do hard-boiled eggs float? What does it mean? The ability of eggs to float happens to be a great indicator of their overall quality. If the eggs float, then they are probably old and not fresh. Recently bought and fresh eggs have fewer microscopic air sacs that prevent the egg from floating.

Read below to learn more about why eggs can float, some tests that you can do before hard-boiling eggs, and how to spot signs of spoilage.

Do Hardboiled Eggs Float?

Eggs are an integral part of the human diet and are enjoyed in several ways across the world. Perhaps the best (and most convenient) way to eat them is by boiling them.

Hard boiling is a simple process where a whole egg is boiled in water until the inside is firm and fully cooked.

This method of preparing and eating eggs is as old as time!

Not only is this an excellent way to get nutrition, but it is also one of the easiest ways to cook eggs with minimal equipment.

Just fill a pot with water, put the eggs in so that they sink, and then turn on the heat! Cook the eggs for 8-10 minutes or as needed and voila. 

You might have noticed that we mentioned that the eggs “sink” to the bottom of the pot before boiling them.

Well, it turns out that this is an important part of preparing hard-boiled eggs because it also determines the quality of the eggs.

Eggshells are made of a combination of calcium carbonate and a bit of protein. The structures are arranged in matrices with a few irregularities that reinforce the overall structure of the egg.

This arrangement gives the egg its durability too.

If you put a fresh eggshell under the microscope, you will notice that it has interwoven textures without any gaps. This is one of the biggest reasons why the egg sinks to the pot!

Since the egg is denser than water and there are no air bubbles around it, it sinks when added to a pot of room-temperature water.

But if you add an old egg to the pot, it will likely float. If you repeat the observation above and swap out the fresh eggshell with the old one, you will notice that the old eggshell has many defects in its structure. These defects occur as the egg ages. 

As air circulates the egg, the oxygen molecules oxidize the compounds on the surface which leads to deterioration. This deterioration usually presents as microscopic gaps or air sacs.

These small gaps allow air to get trapped around the surface of the egg which not only makes it float, but also speeds up the spoiling process!

Don’t worry though, just because you hard-boiled a floating egg doesn’t mean that it is bad.

In fact, the egg may still be good to eat – it is just that the outer shell has deteriorated slightly. 

But for many people, this can be a dealbreaker. A lot of picky eaters usually test the egg in a separate bowl of water to determine its quality.

If the eggs float, then they are usually discarded or, if possible, returned. 

Picking Good Quality Eggs

As per the Food and Drug Administration (FDA), egg manufacturers must properly label their eggs so that they clearly show the expiration date. 

But even before the date is printed, the eggs are first collected using a meticulous manufacturing process.

After the hens lay the eggs, they are transported onto a conveyer belt where they are washed and screened for any lingering chicken feces (gross, we know). 

Once the eggs pass all the quality checks, they are stamped with a batch number and an expiration date.

This date shows how long the egg will remain edible until it goes bad in the traditional sense.

But what they don’t tell you is that the quality of the egg may also deteriorate before the expiration date.

As we mentioned above, old eggs that float in water aren’t necessarily bad, their buoyancy just indicates how fresh or old they are.

In most cases, floating eggs will likely be good to eat but there are also a few quick tests that you can perform to double-check their quality.

We’ll get to the tests in a bit, let’s first take a look at how you can pick the freshest eggs for you and your family.

Here is what to look out for:

Cracked Eggs

Did you know, eggs are lightly tapped by a machine that acoustically checks the eggs for cracks? When a cracked egg is tapped, it gives a slightly different sound than an uncracked egg.

Luckily, you don’t have to do this test as they are already done at the manufacturer’s end.

However, despite the eggs passing this test, they can still crack anywhere from the factory floor to the supermarket. Sometimes a light tap at the right angle is all it takes for the eggs to develop micro-cracks.

These cracks are very small and may be as thin as a strand of hair – but they are enough to cause the eggs to go bad quickly.

The longer the egg is left in storage, the more it will go down in quality, especially around the cracked region. 

This is why we highly recommend that you buy eggs from a reputable store and go for high-quality free-range eggs.

These eggs are sold at a higher price point, but they are arguably better in terms of quality and nutrition – plus they are also animal-friendly!

You don’t have to zoom in and check every egg individually, just a glance should tell you if the eggs are free of cracks.

If you want to be thorough, then you can also check them closely before you shift the eggs to an egg tray in your fridge. 

Expiration Date

A basic rule for always getting fresh eggs is to buy as close to the manufacturing date.

Most stores replenish their stock of eggs daily, but if you live in an area that doesn’t see a lot of footfall in stores, then there is a chance that you might run into older eggs. 

For the best experience, try to get eggs that are manufactured within 1-2 days. You can even go up to 3-4 days – but if you go for week-old eggs then there is a good chance that they will float! These eggs will be safe to eat but they won’t be as fresh.

Signs of Spoilage and Tests

Here are a few quick and easy tests that can help you detect signs of spoilage:

Checking for Color Changes

Eggs are not known to undergo color changes. So, if you notice any odd colors or spots around the egg, then it’s safe to assume that they have gone bad. It is best to discard these eggs, even if they don’t float. 

Checking Surface for Large Cracks

While micro-cracks may be difficult to detect, they don’t immediately put the quality of the egg at risk as it can take time for air to work through these small cracks.

But in the case of larger (and visible) cracks, it is best that you discard these eggs because they might be contaminated!

Cracking the Egg

This method is for people who want to be sure about the quality and safety of the eggs. If you don’t mind eating a poached egg, then we recommend that you crack any eggs that float to confirm whether they are safe to eat.

Crack the eggs in a separate bowl and then check for obvious signs of spoilage like a runny consistency, odd color, dark spots, blood, or a foul odor. If the eggs are free of these signs, then you can either fry them or poach them!

Related Questions 

Hardboiled eggs that float might be old, but they will likely be safe to eat. If you want the best quality eggs, then we recommend that you always go for fresh eggs.

Now that you know all about how hard-boiled eggs can float, here are some related questions:

Can fresh eggs still float? 

The only time fresh eggs will float in water is when you add salt to the water. Salt raises the density of water which in turn causes the egg to float- regardless of its freshness. You can even do a quick and fun experiment at home to see this phenomenon. 

If you haven’t added salt to the water and the eggs still float, then it is likely that they were damaged during transportation.

Do hard-boiled eggs float when cooked?

As the eggs boil in water, the air bubbles caused by evaporation may push the eggs to the top of the pot. This is completely normal and doesn’t reflect the quality of the eggs. It is also possible for hardboiled eggs to float, especially if they crack while boiling. 

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