Your client wants their patio stained. If you’re lucky, it’s clean and ready to go. If you’re not, you may have to remove old stains before you give it the new stain they want.

Unwanted stains can come from a variety of sources—oil, fertilizers, and organics like leaves and pet stains—and each calls for a different stain removal technique.

Removing Oil Stains

Some oil and grease stains can be removed with a strong detergent, a scrub brush, and a sponge. Special concrete cleaners and degreasers are available for tougher jobs. They loosen the oil to make it easier to remove, but don’t break it down, so they work best on concrete that isn’t heavily contaminated. If it is, a poultice made of sawdust, cat litter, or other absorptive materials can be made with a strong solvent to break down and absorb the oil. The downside is that the poultice needs time to work and may not be cost-effective for larger areas. In that case, you may be better off turning to biological warfare.

Microbial cleaners use live single-cell microorganisms to gobble up the oils. When they’ve exhausted their food supply, they conveniently die, leaving the concrete clean and oil-free. It’s the same technology used to clean up beaches and water after an oil spill.

Flushing Away Fertilizer Stains

Because plant food and fertilizers contain minerals like magnesium, iron, copper and zinc, they act very much like the concrete stains you deliberately apply. Because they aren’t water-soluble, it takes an acid solution to remove them. Try a white vinegar diluted 50-50 with water first in a small test area. Apply it multiple times, scrub it in, and rinse. If that doesn’t work, a stronger acid like muriatic may be called for. Dilute it 40:1 with water, but be careful. It can burn skin and eyes and may etch the concrete.

Getting Rid of Organic Stains

Organic stains like those made by plant matter, pet urine and sap are carbon-based making them some of the toughest to remove. Degreasers, acids and soaps don’t faze them. You need to fight fire with fire, or in this case, organics with organics. Like the commercial microbial cleaners that attack oil spills, organic cleaners contain bacteria and enzymes that break down or even eat the stain. You should be able to find them at pet stores, janitorial supply outlets, or on the internet.

You can learn more about how the various types of concrete cleaners work and how to choose the best one for your needs here.

Putting Down a New Stain

Now that you’ve gotten rid of the old stains, it’s time for a new one. You can choose an acid-based stain or one that’s water-based. Acid stains penetrate and react with the concrete, creating natural color variations and mottled effects in subtle earth tones. Water-based stains come in a wide variety of colors and can be mixed like paints for even more hues. Both types of stains can be used for a unified overall look or to create decorative effects for custom looks. For ideas, take a look at this article on ConcreteNetwork.com.

Whether it’s concrete surface prep, cutting, or coring, the right tools ensure results you’ll be proud to show off. Ace Cutting Equipment is your source for rugged, reliable concrete and masonry equipment and supplies.