How To Dissolve Chalk (Calcium Carbonate) When Homebrewing Beer

Beer is 90-95% water, so if you’re an advanced homebrewer, you may have begun investigating ways you can optimize your water to brew the best beer. A key way to do that is to monitor the pH level. Many homebrewers find their tap water pH is too low, meaning their water is slightly too acidic. What can you do to make your water more suitable for brewing?

Add calcium carbonate, or chalk, to your brew water by shaking it vigorously in carbonated water and leaving it to sit for a few hours. Using this water along with your regular strike water will bring up the pH of your beer. Do not add chalk directly to still water or your wort itself, as it will not dissolve.

Read on to find out more about why adding chalk to your water can improve the pH, and the best way to get that chalk to dissolve.

Why do homebrewers add chalk (calcium carbonate) to their water?

If the idea of adding chalk to your beer gives you pause, you’re not alone. The best ways to control pH are a matter of much debate among homebrewers, but most agree that chalk is the best way to do so without negatively affecting taste.

Most experts agree that beer should have a pH between 5.2 and 5.5. Maintaining this level will allow the best environment for fermentation to occur. If the pH of your water is less than that, you may want to consider adding chalk.

To determine if adding chalk will be necessary, the first step is to investigate the quality and characteristics of the water you’re using to brew.

Water quality test strips are an affordable way to get a read on not only pH but the presence of other desirable and undesirable minerals as well. If you live in a city, you may also be able to find water quality reports online.

One of the most intimidating concepts to explore in homebrewing is water chemistry. However, with a bit of basic chemistry knowledge, you can begin to understand how calcium carbonate can improve your homebrew.

What does chalk do to brewing water?

Since calcium carbonate is a base and therefore has a high pH level, adding it is a powerful way to bring up the pH level of brewing water.

By adding chalk, you’re quite literally changing the chemistry of the water. If you do it correctly, this will create a more healthy environment for fermentation to occur, resulting in better beer.

Some brewers like to find out the pH of the water used to make their favorite beers, and try to replicate them at home.

For example, a beer brewed in Munich, Germany is likely brewed with Munich city water. By researching the pH and chemical makeup of Munich city water, you can attempt to recreate that at home!

Why doesn’t chalk mix easily with water?

Calcium carbonate, along with most other carbonates, is insoluble in water.

When added to a glass of water, carbonates sink to the bottom without dissolving. This is because they naturally form super strong ionic bonds which are not easily broken by water. The addition of CO2, however, contributes to the breaking of those bonds.

Because of this, carbonates are easier to dissolve in carbonated water.

How to dissolve chalk when homebrewing beer

Though chalk won’t dissolve in regular still water, it is possible to dissolve it in sparkling water.

You can carbonate your own water using a CO2 tank from your kegging system, or even a Soda Stream, but store-bought sparkling water works just fine too. 

A word of caution: be sure to buy unflavored, unsweetened sparkling water to avoid introducing unwanted flavors into your beer. To be sure, check the ingredients list to confirm the only ingredient is water. Avoid waters with salt, sugar, or natural flavors on the ingredients list.

To prepare your water, you’ll need:

  • Calcium carbonate (chalk) – You can purchase calcium carbonate made specifically for brewing that will have a recommended amount to start with. Northern Brewer’s calcium carbonate recommends using 5/8 teaspoon per gallon of beer to lower acidity by 15%. 
  • 1L or 2L plastic bottle – Be sure to wash any residual liquid thoroughly from the bottle before using. It should be clean and dry when you start.
  • Enough carbonated water to fill the bottle – If carbonating your own water, do it right before you plan to dissolve the chalk. If using store-bought, don’t open it until right before you get started to avoid it getting flat.
  • Funnel – Though not required, a funnel will make it easier to add the chalk to the bottle.

Once you’ve collected all your equipment:

  1. Add the chalk to the empty bottle with the funnel (if using).
  2. Fill the bottle with carbonated water, leaving a bit of space at the top to allow room for shaking.
  3. Put the cap tightly on the bottle and shake hard for a few minutes.
  4. Leave the bottle to sit for 12-24 hours to allow the chalk to dissolve. The water should be clear when it’s ready to use.
  5. Mix with your regular strike water on brew day!

If you still see chalk deposits in the bottle 24 hours after Step 4, repeat the process again with less chalk. Too much chalk will not dissolve easily, even in carbonated water.