Why Do Seashells Smell Bad? Causes and Solutions

Finding and picking up shells is perhaps one of the most compelling reasons to visit the beach. Once you’ve filled your bucket, you can head home and look at the bounty to decide what you want to do with your catch. However, freshly-scavenged seashells sometimes give off an unpleasant odor, and cleaning them before anything is crucial.

Seashells smell bad when there is dead animal tissue inside, the outermost layer (periostracum) isn’t removed, and bacteria or algae are present on the shell. You can clean the shells by placing them in a bleach-water mixture, scrubbing them with vinegar, and boiling or freezing them.

It’s essential to clean a seashell properly before using it for crafts or putting it up as decoration in your home. In this article, we’ll discuss the common reasons why seashells smell bad and how to resolve them.

1. Dead Animal Tissue

A seashell is an outer protection and home of a mollusk. These creatures grow an outer shell they live in and use for protection. Some animals also seek out empty shells to use as temporary homes.

In some cases, these organisms die inside the shell, and a putrid smell is released as their bodies decay.

Most often, your shell-cleaning work will involve removing this dead and decaying matter, which is sometimes tucked away in deep crevices and can’t be reached. Aside from a foul smell, this organic matter can also attract pests, so it’s crucial to get rid of it first.

Fortunately, there are several ways to clean decaying organic matter from a seashell.  

Note: If you find a shell with a living creature inside, be kind and return it to the ocean. Only pick up shells without living creatures to minimize any harm caused to the environment.

How To Fix It 

While there are many ways to get rid of the dead organic matter inside a shell, some shells may be fragile and require extra caution during this process. As such, it’s essential to gauge how thick the shell walls are and choose a cleaning method accordingly.

To learn why some shells are thicker than others, check out my other article: Why Are Some Seashells Thicker Than Others?

1. Boiling

The quickest and most straightforward way to clean up decaying organic matter in a seashell is by boiling the shell, allowing the matter to loosen up from the crevices. For this method, you’ll need boiling water and a pair of tweezers or a toothpick to remove any stubborn specks that stick to the shell.

  • Start by filling a bowl with water at room temperature. 
  • Use room-temperature water as the sudden heat can cause the shell to crack.
  • Completely submerge the shell in water.
  • Bring the water to a boil and allow it to simmer at that temperature for a few minutes.
  • Remove the shell from the water and tilt it so that the organic matter dribbles through the opening.
  • Use a toothpick to scrape out any remnants you find.

You must be careful with this method because too much heat can discolor and even crack the shell.

2. Freezing

Freezing and defrosting your shell is an excellent way to get rid of scraps of animal tissue. It’s best to place the shell in a ziplock bag with water and put it in a deep freeze for a day or two.

Once the bag has frozen over, take it out and leave the shell outside to defrost. When the shell defrosts and you pour out the liquid, any organic matter left in the crevices should come out. You can scrape out any remains with a tweezer or pin.

It’s crucial to allow the shell to defrost thoroughly, or some of this organic matter may remain stuck in the shell, causing the stench to return after a few days.

3. Bleaching

While bleaching may not be as natural as the other methods mentioned here, it’s highly effective and can eliminate more than just dead animal tissue. All you need is a bucket with a solution of equal parts bleach and water. You can add more water and bleach depending on the number and size of seashells.

However, be warned that excessive bleaching or leaving the shells in too long can cause the colors to fade and leave the shell smelling like bleach. So it’s best to use bleach on thicker, sturdier shells, and only for a short time. 

4. Burying

While this seems like an unusual method of cleaning seashells, it’s the most effective. 

As you know, plenty of insects, worms, and microorganisms live in the soil and continuously clean up organic matter deposited here. And they’re tiny enough to get to crevices in the shell that your hands will never reach. So to clean the shell, you can bury it under the surface of a patch of soil where insects and microorganisms will clean it up.

You may also leave the shell on the soil surface, where insects can easily find it. However, the smell of a putrid seashell tends to attract rats and bandicoots sometimes. These critters may whisk the shell away, assuming it’s food, so it’s best to hide it from them.

2. Periostracum and Encrustations 

The periostracum is an outer woven skin that wraps around the shell and is made of organic matter, as opposed to the calcified material the shell is composed of. Often, even when there isn’t a living animal in the shell, the organic periostracum begins to give off a funky smell. 

How To Fix It

Fortunately, getting rid of this outer skin layer is straightforward and requires little effort. All you have to do is soak the shell in a solution containing bleach and water. Consider diluting this solution a little, so the bleach doesn’t damage the shell’s exterior.

You will notice a thin layer or “skin” peeling off the shell. Once you see this, remove the shell from the solution and leave it to dry.

3. Bacteria and Algae

While some shells may seem outwardly clean, their surface is often covered in bacteria, and some parts may have algae stuck on them. If left on the shell, these organisms start to emit a foul odor, so it’s best to remove this possibility as soon as you bring the shell home from the beach.

How To Fix It

The quickest way to clean up bacteria and algae is to put the shell into a bleach-water solution. Again, you want to be careful with how much bleach you add because you don’t want the shell to retain that smell.

After a few hours, remove the shells and allow them to dry under a fan or in the sun. Once the shells have completely dried, clean the surface, edges, and crevices by gently running them over with a toothbrush dipped in a vinegar-water solution. The vinegar should get rid of most  bacteria and clean up any remnants of algae.

Note: Never soak a seashell in vinegar solution, as the acid in the vinegar will react with the calcified shell, causing the shell to deteriorate rapidly.

You can also boil seashells once you’ve buried them and removed the organic matter to get rid of bacteria and other microorganisms.

If you’re using shells with thinner walls, boiling them too long isn’t worth the risk. In this case, it’s best to start cleaning them with a toothbrush and use other, less corrosive methods to eliminate the smell (like burying or freezing).

Emergency Seashell Cleaning Solution

Let’s say you’ve tried cleaning your shell thoroughly using different methods. However, you can’t seem to get rid of the stench. 

Sometimes, you may have a shell with organic matter buried so deep that freezing, boiling, and burying won’t do the trick. 

Fortunately, one method can guarantee a clean shell without too much work. However, this method should only be employed if all else fails, as it’s a little dangerous compared to the others mentioned here. Both for you and your shell.

This cleaning method involves using muriatic acid, better known as hydrochloric acid.

  1. Fill a container with water and pour some acid into it. Ensure you pour the water in first before putting the acid, and the water-to-acid ratio should be 3:1.
  2. Get another container with water and keep it next to the first one. 
  3. Now, wearing protective gloves and using a pair of tongs, pick up the shell and dip it in the acid solution for roughly 3-4 seconds. You may notice some hissing and fizz around the shell; this is normal.
  4. Take the shell out and dip it in the water before placing it on a towel to dry.

This method will clean up any remaining dirt on the shell. However, avoid using it if possible, as the acid can quickly damage the shell.

Final Thoughts 

It’s crucial to clean a seashell thoroughly before using it to decorate your home or create works of art. While cleaning shells may seem like a chore, it’s better than using them without first getting rid of the foul odor. This way, you won’t have to toss them out because the smell is unbearable.

Alexander Picot

Alexander Picot is the principal creator of DiscoveryPit.com, a website dedicated to tips on finding and collecting precious items. Inspired by reading countless adventurer reports from the oldtimers, Alex is passionate about discovering hidden treasures and loves to share his experience with the rest of the world.

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