Is nature leaving its mark on your driveway?
The Hardware Guys tackle stains left by acorns

QDear Hardware Guys,

How do I remove oak stains from a concrete brick driveway?

I hope you can help,
Don Santor

AHi Don, 
We think the problem actually comes from the acorns that are dropping off your trees.

These nuts are high in tannins. Think of acorns like red wine which is also high in tannins and can leave dark stains on clothing or carpeting.

When the tannins are spread over a porous surface, like concrete, the result is a dark stain with a greenish or golden cast that looks like someone threw a pot of tea on your driveway. That’s what is happening when the acorns fall onto your driveway and then the rain washes over them.

Actually, along with using acorns as part of their diet, the Indians used to use acorns to make dye and to tan leather.

But back to your problem -- there are a couple of remedies you might try.

One of the safest is to use a product called CLR.

This mixed with a little warm water and brushed on the area should remove some of the stain. It might require a couple applications, or you could try it full strength.

As with anything you should test a small inconspicuous area of your driveway first to make sure there is no adverse effect.

We feel the best way to remove the stain is to use Muriatic Acid.

Usually available at hardware, paint or masonry supply stores.

This is a product that is extremely corrosive and poisonous, care should be taken when using Muriatic Acid. Wear vinyl gloves, eye protection and old clothes and shoes.

Mix 1 part acid to 20 parts water. It's important to add the acid to the water. You can gradually add acid to the mixture to strengthen it.

Apply the acid with a scrub brush. The solution should bubble when applied to the concrete, if it’s mixed strong enough.

Let it set one to two minutes and then flush with plenty of water from the garden hose.

This should brighten up your driveway nicely. 

Hope this helps you out, 
The Hardware Guys