Unless you're a legendary painter who can do straight lines with only a paintbrush, you need masking tape to make crisp lines between different-colored walls or to make stripes on the wall. You need the right tape, and you need to use it properly, but these steps aren't enough -- you also need a technique to prevent seepage, especially on a textured wall. Two easy procedures ensure clean, straight lines that all beholders can consider legendary.
Use the Right Tape Correctly
Not all types of masking tape are suitable for detail painting, so make sure you read the label before making your purchase. Painter's tape is blue or green; tan masking tape has a strong adhesive that can pull the paint off from underneath it. Some varieties -- which are usually green -- contain a polymer that is activated by latex paint. Because such tape varieties can actually prevent bleeding, they are the best option -- especially for textured surfaces. Clean all dust and grime off the surface before applying this tape, and avoid stretching it as you lay it. Score the edge with a putty knife.
Paint With Two Colors
Painter's tape makes a straight line, but if you want a perfect line with no hint of bleeding, you need to perform one of two procedures. The first is the easier of the two, but you'll need the paint colors on both sides of the line. After laying the tape, paint over the edge that forms the border between the two colors with the color that's underneath the tape, and let that paint dry. It seals the edge, and when you paint over it with the the second color, none of that color can seep. When you carefully remove the tape after the paint dries, no seepage will be evident.
Apply a Bead of Caulk
Some painters prefer to use caulk to reinforce the edge of the masking tape, and it's your best option if you don't have both paint colors. After pressing down the edge of the tape with a putty knife, spread a thin bead of paintable caulk along the edge and wipe it flat with your finger, forcing what remains into the small gap underneath the tape. Paint immediately and remove the tape before the caulk has a chance to dry -- if you wait too long, the tape may pull off your fresh paint.
Make Your Own Sealing Tool
If you're a perfectionist -- and legendary painters usually are -- you may want an alternative to a putty knife, which has a large, coarsely honed blade. You can make your own tool from a short piece of 3/4- by 3/4-inch close-grained hardwood, such as maple or alder. Cut the end at a 15- to 30-degree angle with a chop saw to form a sharp edge, and use this to press down the edge of the tape and tool the caulk. The edge is almost as sharp as a knife, and the wood has enough flexibility to follow textures closely without damaging the wall.