Fixing pH Burn

Have you seen unusual stains and discolorations, often outside your home or business? It could be pH burn (also known as alkali burn), which commonly occurs when a previous painting contractor hasn’t done things properly. If you’ve brought in a painting contractor or coating professional that tested your paint and threw around words like “alkalinity” and “pH’, you’re probably asking yourself why this happened, what causes it, and most importantly, how can you fix it.To help you better understand why and how pH burns occur, we’ll explain the science behind pH burns so you’ll know exactly what the contractor is talking about before he even shows up.

What is Alkali or pH burn?

In simple terms, pH or alkali burn simply means the paint on your concrete, masonry or stucco has started to fade or deteriorate. An alkali or pH burn occurs when the resin or pigments are attacked by the high alkalinity causing in the paint degrade, fade and discolor. The paint will usually have a blotchy and chalky appearance.

Defining pH

What exactly is pH? pH measures acidity or alkalinity of a solution and can be defined as the negative logarithm of the hydrogen ion concentration. When the pH of a solution increases, there is a decrease in the number of free hydrogen ions as well as a change of pH of one reflects a tenfold change in the hydrogen ion concentration. The pH scale ranges from 0 to 14. A pH of 7 is basic or neutral due to the value of water being 7. The pH values from 0-6 means acidity. The pH values 8-14 indicates alkalinity.

Causes of pH Burns

There are two main reasons behind why an alkali or pH burn happens:
  • The pH level of the masonry didn’t have enough time to neutralize before the coating was applied. The surface typically needs neutralize and cure over a period of days to prevent a pH burn. That said, environmental factors can affect how quickly or slowly the stucco neutralizes, including: humidity, temperature, rainfall, wind, and direct sunlight. It must be properly hydrated before painted. This can be sped up by spraying an even coat of water on the surface for several days. Walls that get direct sunlight may need more hydration than walls that don’t.
  • An improper or insufficient primer coat was used. All paints have four main ingredients: pigments, binders, solvents, and additives. Pigments are responsible for the color, the binders bind all of the ingredients together, solvents are the liquids, and additives vary depending on paint type. The pigments in the paints have a reaction with the lime in the concrete mix thus resulting in a pH burn. It is best to use a coating that uses inorganic colorants. Organic colorants offer more vibrant colors but are mostly meant for indoors. Inorganic colorants are more earth-toned colors and typically meant for exterior. In general, it is best to use inorganic colorants when painting as organic colorants are generally more susceptible to pH burns than inorganic ones. It is also recommended to use alkali resistant primers as that can help deter a future pH burn. An alkali resistant primer also stops it from drawing moisture from the coating and causing discolor in the future. The best method for application is back rolling and spray application as it forces the product into any cracks and crevices that may harbor moisture. There are primers on the market that are designed and formulated to withstand high pH levels. The key to these primers is making sure the contractor applies the correct amount and in accordance with manufacture application guidelines. Ensuring the coating properly dries, is the proper thickness, and more are critical to ensure a protective barrier is created.

Testing pH Levels

There are a couple ways to test the pH levels before priming. You can ask your painting contractor. We usually carry them on our trucks, or try your local paint supplier.
  • A pH pencil
  • pH probe with a digital meter
  • PH testing strips
The most common way is with a pH pencil and distilled water. Moisten the surface with distilled water (never use tap water), and mark the surface with the pH pencil. Match the result to the corresponding color on the provided chart.

How to Fix a pH Burn

As mentioned above, there are numerous ways to prevent a pH burn. Allowing ample amount of time to cure, checking pH levels before applying any form of coating or paint, surface preparation with inorganic colorants and using alkali resistant primers are vital steps to insure your home or business doesn’t get a pH burn. However, if it does, there are a couple steps to take.
  • Remove all efflorescence (the powdery deposit on the surface) and allow the surface to dry
  • Apply an alkali resistant primer
  • Use high-quality exterior paint and colors that are specifically meant for exterior use
You’ll likely need a contractor to reverse the damage of a pH burn. Contractors typically charge $40-$50 per hour to repair stucco and that’s not including the materials. All in all, the average repair for fixing a pH burn on stucco would be $400-$700. It’s a nice idea to think that this can all be avoided but at the end of the day, there are always unforeseen aspects in life. Some things are completely out of our control but at least now you know if an alkali or pH burn does happen to your home or business just remember that the paint isn’t always brighter one someone’s home.

Need a quote to repair a pH burn?

Call FLS Painting to request a free quote at 561-704-5568. Our professionals will go above and beyond to ensure your home or business looks its best!.