What condition must be met for proper preparation prior to painting?

For proper preparation prior to painting, ensuring surface cleanliness is crucial. A clean surface allows for better adhesion of the paint, which directly affects the durability and appearance of the finished product. If the surface is dirty, oily, or contains any contaminants, it can lead to issues such as peeling, flaking, or uneven application. Properly cleaning the surface may involve techniques such as pressure washing, sanding, or applying a degreaser, depending on the specific conditions of the surface being painted.

While humidity levels, the type of brush, and color selection are all important factors in the painting process, they do not specifically address the foundational preparation that comes with cleaning the surface. A clean base is vital before moving on to other considerations, making surface cleanliness the key condition to be met for successful painting.