Eggshells in Coffee: Unlocking the Secret to a Perfect Brew

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

Eggshells in coffee
People have been adding eggshells to coffee for decades

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.

So, what’s the purpose of eggshells in coffee?

Adding eggshells to your brew helps reduce coffee’s acidity and bitterness. If you are unsure of the difference between these two taste elements, check out our article acidic vs. bitter coffee

In this guide, I will tell you all about it and how to brew coffee with eggshells properly.

Why Eggshells in Coffee?

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

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

  1. Eggshells reduce the acidity of coffee: Eggshells consist of calcium carbonate, which is very alkaline, allowing them to absorb some of the acidic compounds in coffee.
  2. Eggshells make your brew less bitter: The alkalinity of eggshells lets them absorb some of the bitter flavors of prepared coffee that have been over-brewed.
  3. Eggshells remove coffee stains from mugs and carafes: Grind up your washed shells, combine them with hot water, and pour them into the stained mug. Let it sit overnight, and the shells should absorb the stains, leaving you with a nice bright piece of ceramic in the morning!

How To Prepare Eggshells For Coffee:

Eggs on a blue tray
Always 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 into a small bowl, and the shells set aside in a separate bowl. 

You can separate the eggs into whites and yolks, store them for later use, or cook them 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 and your used coffee grounds in the trash or the compost pile. Check out our article on how to dispose of coffee grounds for more options. 

Eggshells 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.

Types of Coffee Brewing

A hand pouring coffee into a glass with coffee beans beside
Certain brewing processes are better for making coffee with eggshells

Eggshells work with specific brewing processes better than others:

Cowboy Coffee

Making coffee in a basic pot, especially over a campfire, tends to give an overcooked coffee taste. 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 French press and stir to combine before adding hot water.

Drip Coffee Makers

Add shells to the filter first, then the coffee grounds. Place the filter basket in your coffee maker and brew as normal. 


Eggshells are an excellent addition to stovetop 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. 


We do not recommend using eggshells 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 brewing method is slow and, as such, avoids 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 you shouldn’t need eggshells here either. If you like cold-brew coffee, check out our picks of the best cold-brew coffee brands.

Eggshells in Coffee Recipe

Prep Time 10 minutes


  • Coffee brewer
  • Paper towels


  • Water
  • Coffee grounds
  • 1 egg


  • Crack the egg and separate the shell.
  • Wash the shell thoroughly so there are no remains of the egg white or yolk.
  • Cover the shells with a paper towel (to protect your hands) and crush them into smaller pieces.
  • Add crushed egg shells to coffee grounds, using a quarter of the egg shell for one cup.
  • Brew your coffee as usual.

The Final Word On Eggshells In Coffee:

Adding eggshells to coffee can make your brew less acidic and less bitter, improving the taste of your cup of joe. For this reason, the old tradition is still worthy of trying.

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

However, there are other options. Check out our guide on how to make coffee less bitter.

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, the brewing time, and many other factors.

Are eggshells and coffee grounds good for plants?

Yes! Shells contain calcium, while used grounds contain plenty of nitrogen. Both are great for plants. You will find those compounds in most store-bought plant fertilizers. But, instead of spending money, you can use these kitchen scraps and make your own fertilizer.

Is it dangerous to eat eggshells?

Eggs can be contaminated with salmonella bacteria, which can also end up in the shell. Make sure to wash or even boil the eggshells before using them to eliminate any microbes.


  • Aisling O'Connor

    Aisling is an Irish food and drinks writer and journalist fueled by coffee and herbal tea. She followed up her journalism degree with nutrition studies. Find Aisling on LinkedIn.

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