5 Reasons Why Clay Smells Bad (Clay Odor Explained)

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5 Reasons Why Clay Smells Bad

The smell isn’t something you necessarily associate with clay since most of us think about working it with our hands. But did you know that clay does have a smell, and sometimes that smell can be pretty off-putting?

So why does this smell happen? Why does clay smell bad?

In this article, we’ll clarify why clay smells the way it does. This includes clay smelling like it should as well as what it might smell like if it’s bad. Clay has a lot of interesting properties to it that we’ll also discuss, such as how you can clean your clay to remove the bad odor you might smell.

Are you ready to learn more about why clay smells bad? Let’s get started.

Why Does My Clay Smell Bad?

There are many reasons why your clay might smell bad. These causes may be linked in some ways, depending on what you’ve got going on. It also depends on what type of clay you’re using, such as air-dry clay. These smells range in terms of severity from not that bad to extremely unpleasant.

Here are some of the most common reasons why your clay might smell bad.

Fresh Clay and Organic Matter

Generally speaking, clay will smell bad because there’s organic material mixed in with the clay. As time goes on, this organic matter can break down. The decomposing material may give off a stinky odor that isn’t harmful in itself. It also doesn’t mean that the clay has gone bad. It’s just a part of working with clay in general.

making clay mixture


Your clay can grow mold. Most of the time, it’s either green mold or black mold, and it’s not necessarily a good thing if you see either type.

You can remove the mold from your clay by cutting it off. However, if the mold runs through the clay (i.e., it’s been sitting for a long time), you may need to get rid of the clay altogether. Clay only goes bad if it begins to break down or it gets contaminated somehow.

Note that it’s not a good idea to incorporate the mold into your work and think that the kiln will fire it away. Even if the mold spores were to burn up in the heat, the pockets left by the mold could cause an explosion in your kiln.

A Tight Seal and Earthy Smell

digging clay

Clay can smell bad naturally, and that’s a good thing. Many different types of clay, depending on where they were sourced, could smell like a variety of things. People have described the smell as swampy or sulfurous in a way. That’s a normal smell for clay, especially those sourced from the earth.

Cleaning Solution

As we’ll discuss in a later section, you can clean clay with certain solutions. The solutions themselves may give the clay a bit of an odor even after it’s washed off. These solutions include bleach and vinegar, both rather pungent smells for most noses.

Clay is Burnt

burnt baking pottery

If you’re baking the polymer clay in the oven and have let it go for just a little too long, your nose will tell you something’s wrong. Polymer clay that’s burnt will not have a pleasant smell. If you do smell something burning when baking this clay, it’s best to remove it from the oven before anything bad happens.

What is the Odor of Clay?

Not all clays smell the same. Here’s what you can expect the most common clay types to smell like.

Air Dry Clay

There are many smells associated with air-dry clay. For example, every brand might smell a bit different depending on what ingredients they use to formulate their air-dry clay.

drying pottery in the sun

Many people consider air dry clay to be particularly plastic-smelling, not unlike the brand-new shower curtain smell many of us are used to. This plastic smell comes from the components within the air dry clay that give it plasticity as well as flexibility for modeling.

Certain brands of air-dry clay may smell stronger than others. Again, this is due to the ingredients of the air dry clay itself, which varies from one manufacturer to the next.

Polymer Clay

Polymer clay is something you may find in any ceramic studio. This type of clay has a darker colorant that gives it depth as it fires. Since polymer clay does not set up as it dries, and must be fired to cure, it has higher water resistance than air dry clay. That gives it less of a chance of growing mold and turning into moldy clay, as the mold doesn’t have the moisture element to lock on to.

Pottery Clay

We can break down pottery clay into many categories, such as earthenware, stoneware, porcelain, and ball clay. These clays all have various characteristics that dictate the particular smell they may put off.

gathering clays

For example, earthenware and stoneware clays may smell more earthy since they come from materials commonly found in the ground. Porcelain may have a bit of a different smell since it fires at a higher temperature where organic materials are burnt off.

Ball clay is typically referred to as potter’s clay. Like porcelain, it’s a lighter-colored clay that has an earthy smell.

Precious Metal Clay (PMC)

As you may have guessed, precious metal clays typically take on the smell of the metals within the clay. You might get a metallic scent out of them that smells like a wet penny or other coins. These smells might not be as strong as smells from other types of clay, but they are present.

Many crafters use the liver of sulfur to oxidize precious metal clay. This particular substance gives off a very strong sulfurous odor (hence the sulfur component). Precious metal clays that have been treated with liver sulfur may continue to smell bad even after the treatment is complete.

How Do You Get the Smell Out of Clay?

There are a few ways you can remove the smell from your clay. Most of them are inexpensive and don’t require a lot of tools.


spraying vase clay

It is possible to clean mold and any other unwanted organic matter from your clay by using bleach. Simply dilute about a quarter cup of bleach in a gallon of water and spray it on the outside of your clay.

After you let the clay sit for about 24 hours, you should notice a difference in smell. While you might smell more bleach than anything else, this should go away as time goes on. You can also wedge the clay to distribute the bleach and hopefully allow it to evaporate from the clay itself.

Bleach should not interfere with firing but may affect any glazes that are applied before the bisque firing. Be cautious of this if you are planning on using techniques like sgraffito on your greenware.


Vinegar is another solution that leaves your clay stinky but clean. You can add vinegar directly to your clay to clean it, but it’s best to also let it sit overnight and soak. Again, the vinegar smell may take a while to dissipate from the clay, but it should be clean nonetheless.

One benefit to using vinegar to get the smell out of clay is that the clay becomes more plastic. This allows you to manipulate it with greater ease, which can be incredibly useful for those of us who don’t have a lot of hand strength.

Copper Carbonate

copper carbonate powder

Believe it or not, copper carbonate can clean your clay. This particular substance is powdered and looks a bit like a deep blue-green, kind of like the Statue of Liberty. When added to clay, copper carbonate can make a world of difference when it comes to smell.

The key feature of copper carbonate is that it is antimicrobial. Any organic matter that’s breaking down and causing a smell will be neutralized by the copper carbonate and, in some cases, the copper can also prevent further growth from happening as well.

To clean your clay with copper carbonate, simply dilute it into your slip bucket and stir generously.

Copper carbonate can also be added to glazes to clean them as well. However, you should know that the copper can change the color of the glaze if it’s added in larger amounts. That said, a small amount shouldn’t make that much of a difference when it comes to your final results.

Common Questions

Will my air-dry clay projects smell even after they’re dried?

Air-dry clay will smell fresh when it’s taken out of the package, and as long as you don’t let the clay retain too much water, you shouldn’t notice a smell if you let it dry completely.

Does aged clay smell worse than fresh clay?

Clay stink typically occurs after the clay has been exposed to the air and moisture for long periods. That being said, new clay will have a slight odor to it. Aged clay, however, may smell like stinky slop and other organic material that’s been decomposing.

If clay smells bad, does clay soil smell bad too?

Clay soil can stink and even have a pond mud smell, depending on where it’s located. Natural clay soil may smell extraordinarily bad if it’s in a tropical area where the perfect conditions to grow bacteria are prevalent.

What kind of organic matter is found in clay?

The best clay includes just the right amount of good bacteria.

Can I use baking soda to clean my clay?

Baking soda is often used with cornstarch to support polymer clay as it fires. Many crafters will sprinkle baking soda down and then place their clay projects on top during the firing process.

However, you should be aware that baking soda can leach the clay and affect the clay’s workability.

Wrap Up

We hope you’ve found this article on smelly clay useful in your life. Clay smelling bad is a normal thing in most cases, but it’s certainly something to pay attention to as well. The next time you open up a bag of clay, take a whiff and tune in to what the clay is telling you.