Changing the mortar color on a fireplace is a relatively easy way to give the whole room a fresh, new look. Mortar is the grout between the bricks in your fireplace. In addition to providing a solid bond between the stone, it can add to the design and interest of stone or brick.

If you are interested in tackling this simple DIY project, there are a couple of ways to go about it. The easiest ways to change the color of mortar are to either add a new layer of mortar or to use muriatic acid to change the color of the existing mortar. Using either method can quickly update and brighten a room. 

Keep reading for my in-depth guide to changing the mortar color on your fireplace. 


Using Muriatic Acid

Muriatic acid can lighten mortar joints if the current color is too dark for your taste. If the mortar is too dark and you want to lighten it up a bit, purchase a 10% solution of muriatic acid, then follow these steps: 

  1. Apply the solution to the mortar joints using a small bristle brush or similar tool.
  2. Allow the acid to stay on the mortar joints for at least 5 minutes or until it has stopped fizzing. Pay close attention to how long you leave muriatic acid on the mortar, as it can damage the stone or brick if you leave it on too long. 
  3. Rinse the area entirely and allow it to dry. You may need to wait a few days for it to dry completely to see if the process worked.
  4. If the mortar has lightened, but you haven’t achieved the desired result, apply another acid treatment.

Applying a New Mortar Layer

Add a new layer of mortar for more dramatic color changes or to cover cracked or crumbling mortar. With the right materials and preparation, you can repoint your fireplace yourself.

  1. Thoroughly scrub and wash the brick. 
  2. Remove about ¼” of the existing mortar with a hammer and chisel.
  3. Wet the joints.
  4. Fill the joints and any gaps between the firebox floor and hearth with caulk.
  5. Pack soft mortar firmly into place.
  6. Pack soft mortar firmly into place.
  7. Wipe away the remaining residue with a damp sponge after the drying process is complete.

If you plan to tint the mortar with a powdered pigment, be sure to test the color beforehand. Make a few test samples and apply them to a board or piece of scrap wood. Mortar typically lightens as it dries, so allow your samples to dry completely before moving forward with a color choice.

Allow adequate drying time before exposing the new mortar to heat from fires.


Tips for Success

Here are some tips for success when changing the color of your fireplace mortar:

  • Wear safety goggles, gloves, and a mask when working with muriatic acid or chiseling out old mortar to avoid dust and debris.
  • Work in sections, completing one section of mortar joints at a time rather than treating large areas simultaneously.
  • Opt for white or gray cement for a lighter mortar color rather than standard gray. You can also mix in white or buff-colored sand to create a lighter color. 
Today’s Homeowner Tips

Check the weather and allow several days of dry weather for the new mortar to properly cure before exposing it to rain or sprinklers.


Maintaining Fresh Mortar

To maintain your fresh mortar, follow these tips:

  • Avoid fires before the mortar is fully cured because high heat can cause cracking. The curing process usually takes five to seven days, but double-check the manufacturer’s instructions for specific details.
  • Sweep the fireplace instead of washing it with water to prevent eroding the mortar over time.
  • Re-apply mortar sealant every two to three years to protect the joints from moisture damage.

With the right preparation and materials, changing the mortar color can give your rock or brick fireplace a fresh look. 


Should You Change the Color of Your Fireplace Mortar?

Changing the mortar color is a relatively easy DIY project that gives your fireplace and whole room a new look. The process is inexpensive compared to fully remodeling a stone or brick facade. However, proper preparation is crucial, especially when using muriatic acid. The fumes and potential splashing require safety equipment and ventilation. Hiring a professional may be better if you’re uncomfortable working with chemicals or chiseling out large mortar sections.

Overall, changing the mortar hue is an affordable mini-makeover if your fireplace is intact but you want to refresh the color. Always take safety precautions and allow adequate drying time before enjoying the cozy glow of your fireplace again.


FAQs About Changing Fireplace Mortar

How long does new mortar take to cure?

Most mortar takes five to seven days to cure fully, but check the product’s instructions for specific details. Don’t light a fire or spray water on the mortar during this period.


What color should mortar be?

Mortar can be tinted or natural gray. Lighter shades of gray or buff colors work well with stone. However, I recommend considering white mortar as it gives fireplaces a modern look.


How long does mortar last?

With proper maintenance, mortar can last 50 years or more. I’ve found re-applying sealant every two to three years helps protect the mortar, so keep up with this to maximize its longevity.


What tools do I need?

You’ll need an acid-resistant brush, gloves, goggles, and a mask for muriatic acid washing. For repointing, tools include a chisel, a hammer, a trowel, and stirring sticks.


Should I hire a pro?

You should consider hiring a professional mason for large mortar projects or if you’re uncomfortable working with chemicals or chiseling. Professionals have the knowledge and experience to tackle your home improvement project and give you added peace of mind.


Editorial Contributors
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Amy DeYoung

Contributor

Amy DeYoung has a passion for educating and motivating homeowners to improve their lives through home improvement projects and preventative measures. She is a content writer and editor specializing in pest control, moving, window, and lawn/gardening content for Today’s Homeowner. Amy utilizes her own experience within the pest control and real estate industry to educate readers. She studied business, communications, and writing at Arizona State University.

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Casey Daniel

Casey Daniel is a writer and editor with a passion for empowering readers to improve their homes and their lives. She has written and reviewed content across multiple topics, including home improvement, lawn and garden care, sustainability, and health and wellness. When she’s not reviewing articles, Casey is usually playing board games, repainting her bathroom, or quilting.

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