How to Apply Acid to Cement for a Marbleized Effect on an Outdoor Porch

When you're trying to spruce up a concrete deck, patio or porch, you can go with paints or acid stains. The latter will usually create a marble effect because it works similarly to wood stain. When treating wood with stain, the stain will bring out the grain of the wood, keeping the light parts light and making the slightly darker areas more bold. Concrete doesn't quite have a grain, but its components are all different shades of grey. When the concrete reacts to the acid stain, these shades of grey take on the color of the stain to create a marbled look.

Broom
Trisodium phosphate
Scrub brush
Acid stain
Nonmetallic paint sprayer
Nonmetallic scrub brush
Baking soda
Mop
Concrete sealer

Instructions

- 1
  Sweep any loose dirt and debris from the porch. Stir 1 cup of trisodium phosphate into 4 gallons of hot water. Use this solution to scrub the porch. Rinse the concrete thoroughly and allow it to dry in the sun.
- 2
  Mix the acid stain. Typically, you have to mix an equal amount of water into the stain before using it, but products vary. Check your manufacturer's label before mixing. Pour the acid stain into a nonmetallic paint sprayer.
- 3
  Work with a partner to apply the acid stain. One of you needs to operate the paint sprayer and the other needs to scrub the stain into the concrete with a nonmetallic scrub brush. When spraying the stain, start at one corner and move the nozzle using tight, circular motions. Scrub the stain using the same pattern.
- 4
  Allow the stain to dry. As you work and the stain dries, you will notice it bubbling -- this is a normal reaction between the acids and the components of the concrete.
- 5
  Stir 1/2 pound of baking soda into 5 gallons of hot water. Mop the porch with this solution. This neutralizes the acid and will create a lot of fizz. Keep mopping until the porch stops fizzing. You may need to make more baking soda water depending on how large your porch is -- just use the same proportions.
- 6
  Rinse the porch completely and allow it to dry. Apply a concrete sealer meant for exterior surfaces. These product vary in application instructions and drying time, so consult the label for detailed information. Typically, you can pour the sealer into a paint tray and roll it onto the porch as you would with paint, but this varies.

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