Final answer:
When applying primer with a roller, a 3/8 inch nap roller is typically used for smooth surfaces, while a 1/2 inch nap roller is suited for medium textures. Selecting the correct nap size is crucial for achieving a smooth and even coat.
Step-by-step explanation:
When applying primer with a roller for painting tasks, the nap roller to be used depends on the surface texture. For smooth surfaces, a 3/8 inch nap roller is typically used. For medium textures, a 1/2 inch nap roller may be more suitable. It's essential to choose the right roller to ensure a smooth, even coat of primer. Using a roller with too short of a nap will not adequately fill the pores in the texture, while one that's too long can leave an unwanted textured pattern in the primer.
The selection of the nap size is crucial for professional-looking results and will help the primer to adhere properly, creating a good base for the paint. Note that special circumstances or surfaces might require a different nap size, but the sizes mentioned are generally accepted standards for common surfaces.