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The dew point is an important factor when applying floor coatings. It’s the temperature at which moisture in the air condenses onto surfaces, and if the floor temperature is too close to the dew point, this condensation can prevent proper adhesion of the coating. This leads to issues like bubbling, poor adhesion and premature failure. Measuring the dew point ensures your coating has the best chance for success, so it’s important to get it right.

Tools for measuring dew point

Several tools are available to measure the dew point:

  • Hygrometers: These measure humidity and, when combined with the air temperature, can help estimate the dew point using a chart. They’re affordable but less precise than other tools.
  • Dew point meters: These give a direct reading of the dew point, offering a more accurate result than a hygrometer.
  • Infrared thermometers: While these don’t measure the dew point, they are useful for checking the temperature of the floor to ensure it’s sufficiently above the dew point.

Using a combination of these tools can give the most reliable results.

How to measure the dew point

To measure the dew point accurately:

  1. Measure temperature and humidity: Start by measuring the temperature and relative humidity in the area.
  2. Calculate the dew point: Using a psychrometric chart or a digital meter, calculate the dew point from these readings. A dew point meter will give you a direct reading.
  3. Check surface temperature: Use an infrared thermometer to check the floor’s surface temperature.
  4. Calibrate tools: Regular calibration of your equipment ensures accuracy.
  5. Avoid interference: Take measurements away from direct sunlight or drafts to avoid skewing the readings.

Why the dew point matters

The dew point directly affects how well the coating will adhere to the floor. If the surface temperature is close to the dew point, condensation will form, preventing the coating from bonding properly. This leads to problems like peeling, blistering or poor durability.

Coatings like epoxy and polyurethane are particularly sensitive to moisture. Epoxy works best when the surface temperature is at least 5°F (3°C) higher than the dew point, while polyurethane coatings may need an even greater difference.

Ideal dew point range for floor coatings

Each type of coating has different dew point tolerances:

  • Epoxies: Require the surface temperature to be at least 5°F (3°C) higher than the dew point.
  • Polyurethanes: Are more sensitive to moisture and need a larger gap between the dew point and surface temperature, typically around 10°F (6°C).

Always check the manufacturer’s instructions to know the ideal dew point for the specific coating you’re using.

Adjusting for unfavorable dew point conditions

If the dew point is too high or low for proper application, there are a few ways to adjust:

  • Use dehumidifiers: If humidity is too high, a dehumidifier can help bring the dew point down.
  • Increase temperature: If the floor temperature is too close to the dew point, heating the area can help raise the temperature and prevent condensation.
  • Wait for better conditions: In some cases, waiting for better weather or temperature conditions is the best option.

Conclusion

Measuring and controlling the dew point is essential for successful floor coating applications. By ensuring that the surface temperature is well above the dew point, you can avoid issues like poor adhesion and blistering, resulting in a stronger and longer-lasting finish. Taking the time to measure the dew point and adjust the environment when needed ensures a high-quality, professional result.

Sean Walsh
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