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How to Determine the Discoloration of Your Chimney

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Located at the top of your chimney, your chimney crown prevents water from rain and melted snow as well as birds and animals from entering your chimney to cause devastating and costly damage. However, because your chimney crown is constructed from mortar, it can suffer from exposure to the elements, especially since the crown sits on the very top of the chimney. When your chimney crown begins to crack, you will need to contact us at Magic Sweep to get it repaired as soon as possible to keep the cracking damage from worsening. Since it can be very difficult to know whether or not your crown is cracking without getting on your roof, signs of discoloration can let you know if there is a potential problem. We would like to share with you a couple of ways to determine the discoloration of your chimney crown.

Chimney Crown Efflorescence - Chesapeake VA


A crystalline deposit of water-soluble salts, efflorescence is responsible for leaving white stains on masonry materials. If you have noticed white stains at the top of your chimney, it is most likely your chimney crown is also covered by efflorescence. More common in the winter, these deposits can be cleaned off your chimney by brushing a mixture of water and muriatic acid. Efflorescence is often seen as “new building bloom” when it occurs on new construction after the masonry dries; however, if it continues to persist, it is signaling a problem with water penetration and execessive moisture trapped within your masonry chimney. If you have noticed a white film on your chimney, contact us at Magic Sweep so that we can inspect your chimney and make any necessary repairs. The earlier water penetration symptoms are found, the less money you will have to spend on fixing damage to your masonry chimney.

Carbonate Deposits

Appearing as white or gray crusty formations running down your chimney from the top, carbonate deposits, also known as “lime run,” are also indicators that your chimney crown is cracked. What makes these look different from efflorescence is that carbonate deposits will not be crystallized at all. These deposits appear on masonry materials after water trapped within them has been brought to the surface and reacted to the carbon dioxide in the air. Just like efflorescence, carbonate deposits are signs of water leaking into your masonry chimney and should be treated immediately.


Any sort of rust stain should be seen as a symptom of a damaged chimney cap. Your chimney cap sits on top of the crown and covers the flue opening. As one of the least expensive ways to prevent water leaks of your chimney, you should call Magic Sweep to schedule an inspection of your chimney cap to see if it should be replaced.


Another sign of water penetration of your chimney, a mold stain will be dark green, blue, or black and can be fuzzy. Since mold can also be harmful to your health, action should be immediately taken to see if mold is also growing on the inside of your chimney.

Notice any discoloration of your chimney crown? Contact us at Magic Sweep to schedule an inspection of this important component of your chimney system.