Roller Cover Size
Nap refers to the height of the fibers that extend from the backing. For smooth surfaces, choose a shorter nap to evenly apply the paint. Rough surfaces need a higher nap. The longer fibers can reach into the valleys of the textured surface. Some professional painters prefer to "bump up" to a thicker nap for higher production. (1/2" instead of 3/8")
Choosing the right roller cover size is determined by the size of your project. Smaller jobs with narrow hard to reach surfaces may require a 4" or 6" mini roller. The smaller size allows you to be more nimble and precise. Larger jobs may require a standard 9" roller or even an 18" roller to maximize your time. Remember larger roller covers will be cumbersome and may feel awkward to inexperienced users.
Knit vs Woven
Knit fabrics have looped backing with a single pass-through. The result is a more "open" fabric that can pick up and release higher amounts of paint for faster coverage. Use with flats and lower sheen finishes.
Woven fabrics have a backing with a tighter cross-section with two pass-throughs and a twist helps lock down the fabric. This results in a shed-resistant fabric with a smooth lint-free finish. Use with eggshell and higher sheen finishes.
Things to Keep in Mind
A great tip is to do a "W" pattern to paint walls. Start in the corner of a wall and roll on a 3' by 3' "W"; then fill it in without lifting the roller. Repeat until the section is finished. This helps hide seams and any places where the roller has been lifted and put back on the wall again. A fully loaded roller cover will only hold enough paint for a 3’ by 3’ area. Frequently go back to roller pan to reload roller with paint.
A common problem known as "hatbanding" occurs when painters use a paintbrush for cutting in and a roller to apply the rest of the paint, thus producing a different texture along the ceiling and trim. To prevent hatbanding, roll the paint as close to the cut-in areas as possible.
Apply touch-ups using the same painting technique that you used to paint the area. For example, if you originally used a roller, then you should use a roller for touch-ups. If you used a brush, use the same brush for touch-ups. This will keep the area looking consistent with no differences in sheen or texture.
If you take a break while painting, cover rollers in plastic wrap and refrigerate so that you don't have to clean them every time you stop.