Definition

Blocking is a common term in the coatings industry referring to when two painted surfaces stick together when pressed against each other, even after the paint has dried. It can be a significant issue in areas where painted surfaces, such as windows, doors, or cabinetry, come in contact frequently.

Basic Information

Blocking typically arises from using inappropriate paint, improper paint application or unsuitable environmental conditions. This issue often occurs when the paint does not cure fully or when the conditions are not conducive to proper drying. Blocking can be frustrating as it affects the functionality and appearance of painted surfaces.

Common Causes

• Inappropriate Surface Preparation: Not priming or sanding the surface properly before painting can lead to poor adhesion, increasing the likelihood of blocking.

• High Humidity During Application: Excess moisture in the air slows down the drying process, preventing the paint from curing properly. 

• Insufficient Drying Time Between Coats: Applying a second coat of paint before the first coat has dried completely can trap moisture and prevent proper curing.

• Using Low-Quality Paint: Paints that lack sufficient binders or are not designed for high-contact areas are more prone to blocking.

Progression

If left unresolved, blocking can lead to peeling or damage to the paint layers when the surfaces are forcibly separated. Over time, this can compromise the appearance and protective ability of the painted areas and may require extensive touch-ups or repainting. Continued exposure to high humidity or frequent contact can worsen the problem, making it harder for the paint to fully cure and increasing the likelihood of damage. 

Solution

To address blocking, consider the following steps:

• Allow Sufficient Drying Time: Ensure the paint is fully dry before adding another coat. This process will take longer in high-humidity conditions, so it's important to be patient and allow enough time for the paint to cure.

• Improve Ventilation: Increase airflow in the area by using fans or dehumidifiers to reduce humidity levels, helping the paint dry faster and more thoroughly.

• Use High-Quality Paint: Choose a paint specifically designed for high-contact areas, with good durability and resistance to blocking. Paints labelled as enamels, with added alkyds and urethanes, can help reduce the risk of blocking.

• Apply a Protective Finish: Occasionally, applying a protective clear coat to the surfaces prone to blocking can provide a barrier that prevents sticking and adds durability to the painted surface. Make sure to research the type of paint that is to be coated and how it will interact with the proposed clear coat.

• Avoid Contact Until Fully Cured: Keep painted surfaces separated until the paint is fully cured. This may require propping doors or windows open, removing them completely or using spacers between surfaces.

Kindly be advised that these recommendations are offered as a courtesy. We cannot ensure or accept liability for the outcomes achieved through your personal implementation of these methods. Should you require further clarification, feel free to consult a member of our team.