When is it too cold to apply tennis court surfaces? The quick and direct answer is: It must be 50 degrees Fahrenheit (10 Celsius) and rising during application, and for at least 24 hours after. This is very important to ensure curing of the 100% acrylic latex binder.
My tennis court coatings were dry, why is it failing?
As explained in a previous article, there is a difference between drying and curing. The coating must dry first, which means the water in the paint evaporates. This leaves all of the coating molecules, which are unconnected. It looks normal to the naked eye after drying. However, the particles are not melted together or coalesced. If the temperatures fall below the recommended range and the coating gets wet from dew or precipitation, it can be easily damaged.
Application During Marginal Temperatures
You have to be very careful when the temperatures are close to the edge. As a general rule of thumb, don’t even think about applying tennis court coatings when the nighttime lows are forecast to be below 50 Fahrenheit / 10 Celsius. Here are some other important risk factors to consider when temperatures are marginal:
Apply coatings very early in the day, just after dew has dried.
Don’t apply much later than early afternoon.
Sunshine is very important to drying and warmth of the pavement. Shade can prevent drying of coatings for many hours.
Make sure to measure ambient air temperature, as well as pavement temperature. The ground temperature is usually colder than air temperature during spring and fall.
High humidity slows down drying, and coatings must dry before they start to cure.
White lines reflect sunlight and are usually the first coating to fail if not properly cured.
Completing the surfacing process in cold weather
What happens if you start a tennis or sports court resurfacing project, and you run out of good weather part-way through? No worries, you can wait until next spring/summer to finish the job. It’s not worth risking failure and having a major cleanup on your plate. No matter what stage of the coating process you are in, it can wait until the weather is right.
Resurfacing indoor tennis and recreational courts can have a few challenges not common to outdoor tennis court resurfacing. Indoor tennis courts do not have to contend with outdoor enemies like UV rays and harsh weather, but some indoor conditions can wreak havoc, even for the experienced tennis court surfacing contractor.
This article is relevant to all kinds of indoor acrylic courts, including by not limited to:
Acrylic tennis court surfaces are water-based and dry by evaporation. Water is the vehicle that allows the heavy coating solids to be squeegee applied. Once the coating is applied, the water begins to evaporate. If there is not adequate ventilation in the facility, the water can be trapped in the airspace above the courts and slow down the drying of the surfaces. This can cause a “marbled” look on the coating, resulting in light and dark or patchy areas.
Poor ventilation and cooler outside temperatures can also create problems by causing condensation to “rain” down onto the tennis court surfaces. If the inside temperatures are warmer and the ceiling is cool from colder outside temperatures, the moisture can drip onto the partially cured surface, creating blemishes. To prevent both of these issues, make sure to turn on heating or air conditioning systems to draw humidity out of the air. Open any available vents, doors, and windows to allow an escape route for moisture. Large industrial fans can also be rented and help to circulate the air, as well as push moisture out when placed at exterior doors.
If the facility doesn’t have a good way to expel the moist, humid air, you may need to bring in industrial dehumidifiers. Until the high level of humidity is allowed to escape, the coatings will not be able to dry and cure. They will retain the marbled or uneven drying pattern, and be susceptible to damage and early wear. Plus, when the coatings are like this, it will be very difficult to get tape to stick to the surface for painting the playing lines.
Loose Sand On Indoor Courts | Drying & Curing
It is also common to see loose silica sand on an indoor athletic facility, and sometimes on outdoor courts. Court coatings are fortified with silica sand in order to provide a non-slip surface and ideal ball trajectory for speed of play. The latex binders in acrylic coatings need to dry completely before they can cure. Once the full cure is complete, the coatings can coalesce or fully cure. When the full cure happens, the components (sand in this case) of the coating are full bound and locked in to the coating film. In some cases, this can also have the same affect on pigments. If tennis balls become a bit colored from the surface, it is also a drying/curing issue.
The large amount of evaporating water, from the coatings, can take a while to escape from inside the building. This depends on the ventilation, and more importantly, the exhaust system of the facility. When the indoor humidity level is high, it slows down the cure of the coatings. The silica sand can be rolled out of the coatings and or can migrate out if very humid. There is no need to worry about this, as it will slow down and stop as the full cure is reached.
The quicker you can get the interior humidity level lowered, the sooner the sand roll-out will cease. Here are a few things that can help:
Rent big agricultural fans and point them outside, by an open doorway to exhaust interior humid air.
Turn up the heater and run all fans to keep air moving, with the main focus on exhausting the moist air at the same time.
Air conditioning takes moisture out of the air. Just keep a balance of using AC and heat, since heat helps the curing process more than cool conditions
Industrial dehumidifiers can also be used to bring inside humidity levels down. Check with local equipment rental stores to find ones for rent.
Also ensure that the slab/ground temperature and air temperature is well above 50 degrees F. Warmer is much better, but acrylic binders cannot cure when the temperatures are below 50 degree Fahrenheit / 10 Celsius.
Another common problem with surfacing indoor tennis courts is application of coatings on a very smooth surface. Indoor courts do not benefit from the wind and rains, which actually help to move debris off the surface. Dirt and sand particles, that come out of the surface, become abrasive to color coatings under the scuffing of tennis courts. Long-term, this can create a very smooth surface which makes it difficult for application of color coatings. The application squeegee can wipe the coatings off of a smooth surface, and leave a very thin coating. This can sometimes cause irregular color patches or inconsistent textures on the surface. To prevent this, apply the first coat of Acrylic Resurfacer (properly mixed with sand and water) with a squeegee, but follow directly behind with a soft, horse hair-type broom or brush. This puts a fine grooved text in the coating. Once the first coat of Resurfacer is dry, squeegee apply another coat of resurfacer, going the cross-direction. This allows the second coat of resurfacer to “grab” onto the groove finish and deposit a complete textured coat. At this point, the surface is ready to accept the tennis court color coating surface layers.
One of the most understood topics and frequently asked questions are, “what is the difference between drying and curing” when it comes to tennis court paint and coatings.
Acrylic sport coatings are water-based, and latex is the binder or “glue” that adheres to the pavement or existing acrylic surface. The binder also locks in all of the components of the coating system, like pigments, sand, and other proprietary ingredients. Water is the vehicle that thins the coating solids so that application by squeegee can be achieved. Once the coating is applied, the water evaporates leaving the solids of the coating in a consistent film. This evaporation is “drying“.
At this point, the film solids are dry. They can even be walked on without a problem. However, all of the components of the coating are not entirely connected and bonded in a strong film. In order for the coating components to properly coalesce, or “melt” together, it is important that the film remain mostly dry and in temperatures above 50° Fahrenheit. This is especially important within the first 24 hours. This is “curing“.
If the coating is not allowed to achieve this initial cure, the components like sand and pigment can wash or roll out the film can fall apart to varying degrees. The level of damage or failure depends on how marginal the cure.
Many coating and paint specifications include the statement “product shall be applied when temperatures are 50° and rising”. This means start coating in the morning when the temperatures are at least 50° and getting warmer, not late afternoon or evening when temps are dropping.
Remember, the coating must dry before it can begin to cure. Starting application late in the day puts the film at risk of dew and cooler nighttime temperatures. A good rule of thumb is to avoid acrylic paint and coating application on days when the nighttime lows are forecasted to drop below 50°. If the daytime highs are not very warm and it is cloudy, or the courts are heavily shaded, you also need to take that into consideration. The shade will increase the drying time and affect the temperature of the court surface. These factors affect drying and curing.
If you are forced to push the application on marginal days, you may want to use an infrared thermometer to check the surface temperature. Pavement absorbs and holds cold for longer than most people think. In Spring and Fall, the sun is further away and not as intense. The pavement surface isn’t able to warm up as quickly as it does in the summer.
If you are a contractor and your customer is pushing you to apply when the temperature and weather is not within acceptable range, make sure to provide them with a copy of the coating manufacturer’s specifications and ask to reschedule application when conditions allow.