DIY Choosing a Paint Roller
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When choosing a paint roller, first consider the condition of the surface you are working with. The surface texture will dictate more than anything else the length of the nap needed to get good coverage. For instance, a rough surface like drywall texturing will require a long nap of 3/4 inch or more, while a smooth surface like wood or wallboard will be best treated using a medium or short–napped roller.
After the surface condition, the coating type and finish will dictate the length, as well as the material of the nap to choose. For instance, when using high–gloss paint, oil or polyurethane varnish a short poly/wool blend nap of about 1/4 inch is the best choice, particularly when applying these finishes to a very smooth surface. Check the quick reference chart below for help choosing a roller by surface and finish.
Choosing a Roller Nap
The nap or absorbent fiber of a roller is available in lengths of 1/4, 3/8, 1/2, 3/4 and 1 inch and is made using wool, mohair, nylon, polyester and poly/wool blends. In addition to these traditional materials used to make roller nap, high density and polyurethane foams are commonly available for rollers and brushes.
Of the materials available, polyester is easily the most widely used to make both high and low quality roller nap. Natural wool has been used for sometime to make high quality rollers for oil paints and varnish but the trend is now toward a blend of wool and polyester for these coatings.
The nap material to choose for your project will depend on the finish and vehicle of your coating. For oil and alkyd coatings, paints with a glossy sheen, as well as clear coats like varnish and polyurethane, a poly/wool blend is the best choice to keep roller fibers out of the finish and produce a smooth, uniform coat. For latex paint of any finish, a polyester nap is a good choice for good coverage and a smooth finish.
Choosing a Nap Length
As a general rule use a short nap roller for shiny and oil–based paints or varnish, a medium nap for flat and eggshell paints and a long nap for any coating on rough surfaces like drywall texturing and brick or when painting hard to cover materials like bare masonry. A long nap roller will create a great deal of spatter as it rolls so it should be reserved for situations like these where the paint must be forced onto the surface.
Choose a short nap roller of 1/4 to 3/8 when you have a very smooth surface to paint with a shiny finish. This would include applying high–gloss paint to drywall or plaster and when painting wood like kitchen cabinets or built–ins with a glossy finish.
Choose a medium nap of 3/8 to 1/2 inch for most paint jobs around the house including walls and ceilings. These will produce a consistently smooth coat with minimal spatter and roller marks even when using an egg–shell or semi–gloss finish.
Choosing a Roller Size
Roller covers or sleeves are made to fit onto roller handles or frames, which can then be threaded onto an extension pole for a longer reach. Typical sleeves you will find at paint and home stores include 4, 7 and 9 inches and are made to fit onto a wire frame. In addition to these, mini or sausage rollers are available for small and hard to reach spaces such as shelves or inside kitchen cabinets. These are about 6 inches long and 1 inch round and made to fit onto a long, thin handle.
Choose the size of your roller based on the size of the area you need to paint. The standard 9 inch roller is a good choice for painting rooms including the walls and ceilings. A 4 inch roller can be a good choice for painting woodwork like shelves and built–ins but in most of these cases a sausage roller is a better choice. The 7 inch roller may be a good choice if you're not comfortable with the slightly larger 9 inch length but as a separate tool it doesn't offer any particular advantages over the standard roller.
Choosing a Quality Roller
Always choose a good quality roller for your project, especially when painting inside the house. A high quality roller will cost just a little more than a cheap roller and will last much longer, making it more economical in the long run. You can usually rely on the price to correspond to quality when choosing a roller but not always, so look for a few telltale signs.
First, the nap on a cheap roller is not as dense as it is on a top quality roller. To test nap density wrap you hand around the roller and squeeze. You should not be able to feel the inner core on a quality roller when you squeeze it in your hand. Even if it's a short nap, it will still have plenty of cushion between your hand and the core. Hold two rollers of differing price at the same time to feel the difference in nap thickness.
Another test of roller quality is the core itself. A cheap roller will have a cardboard or hard polymer-bond plastic core while a quality roller will have a phenolic resin or polypropylene plastic core. The quality roller will stand up to many paint jobs and can be washed repeatedly. The cardboard in cheaper rollers will breakdown after only a couple uses and, even with a plastic core, the nap on a cheap roller will shed excessively, leaving fibers in your paint finish.