Decorative landscape rocks are magnificent additions to any outdoor space. In fact, your entire landscaping could revolve around a few strategically placed rocks. However, the satisfaction dissipates when these rocks start turning brown and degrade the whole appearance of your yard.
Landscape rocks turn brown due to aging, iron oxidation, acid rain, mineral interactions, and the buildup of dirt and grime. Common solutions include cleaning the rock with oxalic acid, muriatic acid, and household cleaning agents. You can also use a sandblasting unit.
In this article, we’ll discuss the reasons why your landscape rocks are turning brown. We’ll also go over several solutions you can try.
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Why Your Landscape Rocks Are Turning Brown
Light-colored rocks are popular in landscaping because they fit most design themes. They can perfectly complement water features, plants, sculptures, and more. However, they don’t stay the same color forever.
Over time, your formerly beautiful landscaping rock will change, taking on a less pleasant brown or rustic appearance. Here are some of the reasons for this phenomenon.
Iron oxidation is one of the most common reasons for light-colored rocks turning brown. Iron oxidation happens when the rocks interact with oxygen and water (source).
The interaction results in a coat of hydrated iron oxide on the rock surface, which appears as a rustic brown or yellowish hue. Oxidation happens more quickly in rocks regularly exposed to water.
The aging process in rocks can be referred to as weathering (source).
The rock’s top layer will wear away during weathering, exposing underlying elements and minerals. If the minerals are brown, you may also notice the rocks changing to reflect the color.
Prolonged exposure to minerals in the landscaping environment can cause them to turn brown. If your rocks are in areas where runoff from fertilized garden areas can settle, they may change to brown over time.
Similarly, mineral interactions may happen if the soil around the rocks is mineral-rich.
Acid Rain and Snow
Acid rain and snow often contain sulfuric acid and nitric acid. Prolonged exposure to these elements can change the color of your landscape rocks.
Depending on the level of acidity, the color change can happen quickly or in smaller, drawn-out increments. If your area has a history of acid rain, you should expect discoloration over time.
The Buildup of Dirt and Grime
Dirt and grime can also give light-colored rocks a brown hue. The extent of the browning depends on the type of dirt and grime the rocks are exposed to. Rocks around unkempt water features may develop a coat of brown sludge.
Similarly, landscaping rocks around your household or industrial debris may interact with some of the waste, leading to discoloration.
3 Solutions for Your Landscape Rocks Turning Brown
There are a few solutions to reverse the color of brown landscape rocks. Most of them require you to mix some chemicals, while others involve using some machinery and manual labor.
1. Wash the Rock With Oxalic Acid
Oxalic acid is a safe cleaning agent you can find in your local hardware or home improvement store. It’s often sold as wood bleach.
It dissolves the iron oxide responsible for the rock’s brown color. However, the response to oxalic acid will vary from one stone to another. It’s a good idea to test a small sample before you choose this route.
Follow these steps to wash your rock with oxalic acid:
- Pour a pound of oxalic acid into a gallon container filled with ¾ water.
- Stir the crystals to dissolve them, taking care not to inhale the powder.
- Pour some hot water to fill up the contact.
- Put the rock in another container and pour the oxalic solution until it’s submerged.
- Wait a few days for the brown color to wash off.
- Remove the rock while wearing protective gloves.
- Put it in a tub of clean water and change the water until it’s completely rinsed.
2. Wash the Rock With Hydrochloric Acid
Hydrochloric acid is a popular rust remover. You can find it in stores as muriatic acid. It comes in one-gallon containers. However, it’s even more dangerous than oxalic acid.
You must wear adequate protection before cleaning the rocks with a muriatic acid solution. You’ll need to protect your eyes, skin, and hands. You should also wear old clothes to avoid ruining anything valuable.
Hydrochloric acid works well because it removes carbonates such as calcites and also aggressively removes iron oxide rust.
To wash a rock with hydrochloric acid, follow this process:
- Wash your rock in clean water to remove all loose dirt and sand.
- Place the rock in a large container and pour in your hydrochloric acid mix.
- Allow the solution to sit for five days in a shaded area.
- Take out the rock and neutralize any acids left by washing it with a solution of baking soda.
3. Remove the Top Layer With a Sandblasting Unit
A sandblasting unit can wear off the deposits causing the brown coloration, giving you a more natural appearance. Chisels and scrapers can achieve the same results, but they will take much more work.
You should also remember that sandblasting may cause breaks and cracks. It’s best to work as slowly as possible.
You’ll need to hire an air compressor and a sandblasting unit for the project. You also need to choose a medium powerful enough to remove the minerals responsible for the brown color.
Discolored landscape rocks can ruin the aesthetic appeal of your garden. Fortunately, there are a few solutions for reversing the damage and getting your rocks looking their best again.
After you get rid of the brown color, you’ll want to take some steps to ensure the rocks don’t lose their shine again.
Basic approaches like protecting your rocks from acidic rain and mineral-laden runoffs can go a long way. Additionally, you need to create a routine for washing off grime from the rocks. Proper care can significantly slow discoloration, making it easier to control.
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