How to get white (efflorescence) stains off of brick and metal

Home ownership is a whack-a-mole of projects.  As soon as one thing is fixed or completed something else pops up.  Something can be newly renovated and a year later it already needs upkeep.

The Brick and the Patio

When we built on the extension at the back of the house we finished it off in brick to match the rest of the house.  The deck/balcony is finished with a bluestone.  When the work was in progress we had several discussions about drainage and wanted to avoid putting in an unsightly drainpipe.  The solution we came up with to slightly pitch the surface away from the house and put in a weep hole to let excess water that seeps into the stone pour out.

The unfortunate result was that when water did seep out it brought with, what we learned, was something called an efflorescence residue that stained the brick outer wall, the bluestone patio as well as the outer doors to our bedroom.  We corrected the problem by removing the weep hole and sealing the stone with waterproof grout and a sealant on the terrace but we still had the stains to deal with.

Efflorescence:  is the migration of a salt to the surface of a porous material, where it forms a coating. The essential process involves the dissolving of an internally held salt in water, or occasionally in another solvent.

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We had several failed attempts at cleaning it.  We tried scrubbing with soapy water, then power washing and various cleaners from the hardware store.  Only one thing worked: Klean Strip Green Safer Muriatic Acid Jug 128 Oz

You have to be extremely careful using this product as it is very corrosive.  USE THIS PRODUCT ONLY FOR BRICK AND BLUESTONE.  We put up plastic to protect the painted doors.  Follow the dilution directions exactly.

Materials:

  • industrial rubber gloves
  • eye protective wear
  • spray bottle
  • a bucket to dilute the solution
  • scrub brush

Here’s a tip: don’t use an orange Home Depot bucket–we had slightly peach-colored grout on the patio for months!

Carefully spray the diluted solution on the brick so it does not splash in your face (wear protective glasses).  When the acid hits the efflorescence it will fizzle a little. Then use a scrub brush to loosen the efflorescence.  Next, use a power washer or hose to rinse off.  We couldn’t believe how well this stuff worked. It even removed green moss that can grow on the brick after the rainy season.

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For the bluestone patio, we did not have to be so careful and poured the diluted solution directly on the stone.   You will see the solution going to work on the stains straight away.  Use the scrub brush to loosen the efflorescent residue a little at a time.  When complete, power wash the area and repeat process if necessary.  It also helped with the grease and other stains from food, candle wax and spilled red wine from all the awesome BBQs we had over last summer.

Then once the patio was clean we sealed it with Miracle Sealants – 511 Impregnator Penetrating Sealer 128 oz. – Gallon to protect it from stains in the future.

The Doors

Our painted metal clad Marvin doors had to be treated with more delicacy.  We were told a diluted CLR solution would work.  We tried this and it was a lot of work to scrub the surface clean of the residue and you have to be sure to rinse immediately because technically CLR is not for painted surfaces.  After several days of cleaning only small patches, we turned to the internet and discovered that vinegar can work as well.  The best part is that it is safe to use, cheap, and required less scrubbing than the CLR.  You can use it undiluted.  We recommend that you use a soft scrub sponge so you do not scratch the paint.

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The process took several days to complete because after scrubbing for an hour or two, your wrists get sore.  See the clean area on the door to the right below.  In between using this method we alternated between scrubbing and power washing. It was labor intensive but we eventually got the doors (mostly) clean.

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