Question: Help, please! The fireplace in my 1972 home is made out of something like lava rock and the previous homeowners put dirt in the holes so they could plant moss (who came up with that stupid idea?) I have managed to get most of the dirt out of the holes, but do you have any ideas about what I can use to clean the rocks so they don’t look so dusty and old?
Joanne B., Spokane
Answer: Joanne, thanks for the photo and for chatting with me on the phone. I’ve built a lot of stone backgrounds for free-standing stoves, but have never cleaned the stone.
After consulting with pros and going with my gut instincts, here’s what I would do if this was my fireplace:
Because it is natural basalt rock, I would clean the fireplace using air. I would contain the fireplace by constructing a tent from plastic all the way around it, leaving enough room for ladders and scaffolding. Since one side of your fireplace is two stories high, scaffolding is highly recommended for a safe and comfortable working platform.
You also have a popcorn ceiling and the home was built in 1972, so the likelihood that the ceiling contains asbestos is great. I would use pushpins to fasten the plastic to the ceiling to protect it from the dust and from being disturbed from the air. I would use painters tape up against the edge of the fireplace, to attach the plastic and cover the exposed walls within the tent. To protect the carpet on both sides of the fireplace, I would cover it with painter’s tarps or completely pull the carpet and pad back out of this area.
All the tools needed for this project can be rented. The air compressor should stay outside the tent as should the wet and dry vac. However, vent the vac’s exhaust to the outside to prevent dust from circulating throughout your home. Also, turn off your furnace fan to prevent circulation of the dust throughout your home.
Set the air pressure so you can get close to the rock to remove the debris and dust from the crevasses, but not so high that the debris blows back into your face. Start with the lowest setting and work your way up to find the pressure that is just right for the project. Of course, you’ll want to wear a mask and eye protection. With the air in one hand, use the other hand to hold the wet and dry vac hose and suck up the debris, as you use the air. The vac’s hose should be as close as possible to the air nozzle to be effective.
Start at the ceiling and work your way down to the floor. At the top use a paint shield with a handle near the ceiling when you first start off. This will prevent the air from blowing directly into the ceiling. Get a helper to hold the paint shield and use counter duster to sweep down the rock.
This will effectively remove the dust and dirt from the rocks and mortar. If you prefer, you can hand wash the rock afterward using a solution of one cup of white vinegar to one gallon of warm water and a white cotton rag that won’t snag. Cover the floor with plastic to catch the water.
If you’d like to give some life to the rock and a more uniform color to the mortar, you can apply a sealer to the entire fireplace. The sealer products described below are sold mostly at contractor’s supply houses.
Before you commit to a sealer, first find a couple of basalt rocks and test the products because most sealers have a high sheen. However, if you don’t like the sheen, you can knock it down a bit. For example, you can apply SureCrete’s Hi-Gloss Sealer, and after it dries you can wipe the surface with a rag soaked in Xylene (and wrung out).
It’s possible that the manufacturer’s solvent could be added to the sealer to thin it to help knock down the sheen. The manufacturer also may have other recommendations so it would be wise to contact them. This process will smell up the home, so make sure you have lots of ventilation.
One product I have used on basalt rock is Chemstop from Tamms. It’s a heavy-duty clear water-repellent compound. It takes two coats to get some life from the rocks, but it’s messy to use because it’s so watery.
This project is going to be messy and time-consuming, and you’ll spend more time getting the project ready than actually doing the work. This may be a good project for a pro.
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