Most property managers are somewhat familiar with the terms “acid wash”, or “chemical clean”. But how can you determine with certainty if this is needed? And what factors should you consider before booking the service? Below, we will answer these questions and provide some helpful guidelines around booking your next acid wash.

Why does the building need this?

So, you just had the windows cleaned on a building you manage, and were told “This will need an acid wash”. 

Those comments may have come directly from your service provider, or may be the result of several complaints from residents, pointing at their stained windows and demanding better results. Whatever the case, the cause of staining on glass will generally fall into one of two categories:

1. Construction debris: On newer buildings, it is not uncommon to find that the initial post-construction clean was not done as thoroughly as required. We quite often find remnants of silicone, paint or exterior membrane that was not cleaned off properly. It is also very common to find mineral deposits or concrete slurry resulting from rain water dripping down from the unfinished concrete slab and onto the glass, during the construction process. An acid wash or chemical clean will definitely be needed to remove those stains. 
2. Mineral deposit accumulation or hard water stains: This type of staining occurs over time, and is caused by rain water hitting various surfaces on a building. The raindrops pick up minerals, and subsequently drip down and dry on the  glass, leaving stains that look like water spots. This is very common on brick buildings or buildings that have elements of uncoated concrete or aluminum. 

In both instances, an acid wash will be required to remove those stains.

Example of glass and window frames stained with minerals leaching from brick and mortar above.

Example of stained railing glass resulting from water hitting the concrete pavers and splashing on the glass and staining it over time

What does the process look like?

The most effective product to remove mineral deposits from glass surfaces is hydrofluoric acid. This product is extremely toxic and presents a serious health hazard to workers if not handled with proper care. It also has the potential to damage glass and other surfaces it comes in contact with, so doing your due diligence and hiring experienced professionals is key.

The process usually entails application of diluted acid to the affected windows, followed by thorough scrubbing using mops and non-scratching scrubbing pads. The glass, gaskets, window components and surrounding areas are then thoroughly rinsed using a low-pressure hose. For a perfect finish, we will sometimes recommend to follow the acid wash with a regular squeegee clean, as the process can leave drips and water spots behind. Work can be performed from ropes, swing stage, or a boom lift.

Is timing important?

Most people associate window cleaning with sunny summer weather. However, when it comes to chemical clean or acid wash, cooler cloudy or rainy weather is best. Here is why:

1. The chemical absolutely cannot dry on the glass: If it does, it may etch it and permanently damage the windows. This makes working in the sun near impossible and the whole process much more difficult.
2. Worker safety is paramount: That’s why when working with dangerous chemicals, a full rubber suit and gloves are required which become extremely uncomfortable to wear in the summer heat.
3. Cost Savings: There may be cost savings in having this done in the off season. Window cleaning companies may offer better rates once the peak summer season is over. Also, performing this work in the rainy season may allow you to eliminate the final step of detailed squeegee clean, hence eliminating that extra cost altogether. 

In Summary 

Now that you have all the information on hand, you are ready to book your chemical clean. Here is a quick summary of what you will need to make your project a success:

• Understand the issue – Is this an existing building with staining that happened over time, or is this a new project in need of a post-construction clean? If dealing with more than just staining, a full post-construction clean might be needed, and an acid wash may not be sufficient.
• Vet your service provider – Do not be afraid to ask questions! Ask about the process. Ask for a Safe Work Procedure document specific to chemical clean. Ask about the product used and the MSDS sheet. Make sure to get at least two references that back the legitimacy of your provider, and ensure that the references are specific to acid wash.
• Discuss Timing – Make sure your clients understand that optimal timing for this work is different from regular window cleaning. This will make booking the service easier and may also save your clients money.

Of course, if you have any questions around acid wash or post-construction cleaning, we would be happy to answer them. Our team has over a decade of experience in post-construction work and has developed clear safe work procedures around acid cleaning.