Why Do Some People Put Eggshells In Coffee?

Have you ever seen someone add eggshells in coffee? Do you wonder about the reason behind it? We’ve got an explanation for you!

Close-up of white and brown eggshells
Eggshells added to coffee grounds is an old practice

Adding eggshells to coffee grounds is an old practice–many people remember their grandparents doing it. It’s less common than it used to be, but some people still swear by it.

My parent’s generation has an old stereotype of cowboys and farm wives adding crushed eggshells to their coffee before brewing. It’s become uncommon in the last few decades due to all the different types of brewing methods that have become trendy, but there are people who still swear by it.

So what’s the purpose of adding eggshells to ground coffee, and how do you go about it properly?

Read on to find out!

Why Eggshells?

The shells from cracked eggs seem like a weird thing to put in coffee grounds. You don’t want to give your coffee a raw egg taste, after all. So what’s the purpose behind it?

There are several reasons why it might be a good idea.

  1. Eggshells are mostly comprised of calcium carbonate, which is very alkaline. This gives it the ability to absorb some of the acidic compounds in coffee.
  2. Its alkalinity lets it absorb some of the bitter flavors of prepared coffee that’s been over-brewed.
  3. Eggshells can also remove coffee stains from mugs and carafes.

How To Prepare Eggshells For Coffee

white eggs placed in a tray
Use raw, uncooked eggs

If you decide to add eggshells to your coffee pot, there are a few things you should do before and after brewing.

First, do not use shells from hardboiled eggs. Eggs release sulfur compounds as they cook, which permeate the shells and can add an unpleasant flavor to your finished cup of coffee. Use raw ones instead.

The shells should be carefully cracked, their contents emptied out into a small bowl, and the shells set aside in a separate bowl. 

The eggs themselves can further be separated into egg whites and yolks and stored for later use, or they can be cooked up for breakfast alongside your coffee. Your choice!

Before brewing, wash the shells under cold water to remove all bits of egg and membrane–this is important for preventing an eggy flavor from getting into your finished cups of coffee.

After brewing, discard the eggshells along with your used coffee grounds, either in the trash the compost pileEggshells and grounds are a great addition to compost! Not only are they rich in calcium, but they also contain trace amounts of potassium and phosphorus. If you like this post, you might be interested in our Breakfast Tea vs. Afternoon Tea guide.

Types of Coffee Brewing

coffee, drinks, roasted
Certain brewing processes are better in making coffee with eggshells

Because eggshells are best used for reducing the acid in a cup of joe, it works with certain brewing processes better than others:

Cowboy Coffee

Making coffee in a basic pot, especially over a campfire, tends to give an overcooked coffee taste, and the eggshell method is strongly associated with it for this reason. Add crushed, washed shells to the pot with your grounds to improve the taste.

French Press

Add a small amount of washed, crushed eggshells to the coffee grounds at the bottom of the pot and stir to combine before adding hot water.

Drip Coffee Makers

Add shells to the filter first and then add the coffee grounds on top. Place the filter basket in your coffee maker and brew normally. 


Eggshells are a good addition to percolators because of the way they work. Hot water is run through coffee grounds repeatedly, making a strong, acidic brew, so adding some crushed shells to the grounds before brewing tends to give a smoother cup. 


Shells are not recommended when brewing espresso as they can throw off the flavor balance and destroy the crema layer. If you want to reduce the acid in espresso, you’re better off buying low-acid espresso beans.

Pour-Over Coffee

Shells aren’t recommended for pour-over coffee, because this type of brewing is slow and careful to avoid acidity and bitterness. You shouldn’t need to add eggshells if you do it properly.

Cold Brew

Cold brew coffee is the least acidic of all brewing types, so eggshells shouldn’t be needed at all!

You might also be interested in our Geisha coffee guide.

The Final Word On Eggshells In Coffee

One last thing that eggshells can do is remove coffee and tea stains from well-worn mugs and carafes. 

Grind up your washed shells, combine them with a little hot water, and pour into the stained mug. Let it sit overnight, and the shells should absorb the stains, leaving you with a nice bright bit of ceramic in the morning!

No matter what purpose you need eggshells for, they are an inexpensive, easy-to-prepare ingredient for making a better cup of coffee.

Eggshells In Coffee FAQs

What are some other ways to make coffee less acidic?

Other ways to reduce the bitter or acidic taste of coffee:
1. Add a little milk
2. Add a bit of salt to the grounds before brewing
3. Try making pour-over coffee or cold brew
4. Purchase low acid coffee beans

What is the acidity of coffee?

The average pH value of coffee hovers around 4.85 to 5.10, which is on the acidic end of the scale. The acidity level can vary due to how dark the beans are roasted, how long the brewing time is, and many other factors.

Are eggshells and coffee grounds good for plants?

Yes! Shells contain calcium while used grounds contain plenty of nitrogen, both of which plants need for healthy growth. They are often included in plant fertilizer, but why spend the money when you can just use your kitchen scraps?

Is it dangerous to eat eggshells?

Not necessarily. Eggs can harbor salmonella bacteria, so if you do decide to consume them it’s recommended to boil the shells in water first to kill any bacteria. 

The easiest way to consume them is to grind them into powder. They have been used as a natural calcium supplement for hundreds of years, and are easily absorbed.


  • AE Inman

    A E Inman is a direct response copywriter and humor blogger. When she's not poking fun at her attempts to start a writing business, she can be found in the tea aisle of her local import store, arguing with strangers over the merits of rare tea varietals. She enjoys writing copy while consuming copious amounts of coffee and gunpowder tea.