I tried the green painter's tape, but found it to be not sticky enough. I use regular masking tape - lay out strips of it on a clean sheet of glass, then use a sharp blade to remove the factory edge(s). This gets rid of the nicks and dings that accumulate while the tape is still on the roll, plus eliminates the edges where the glue is weakened due to exposure to the air. The application on the glass also helps to cut the "grip" of the tape slightly.
The surface to be painted should be thoroughly clean before painting or masking, and if you're applying the tape over painted surfaces, the paint should be
completely dry. Use reference points on the model, such as moulded-on details, to keep the tape line straight, or use dividers or calipers to transfer measurements from the model to the tape, then cut the tape while still on the glass - this works well when a stripe or colour change occurs partway up the side of a diesel's hood or cab. You can also transfer measurements from a decal sheet to ensure that heralds and striping end up where they should be in relation to colour separations.
The tape can also be used as a measuring device, as was the case with the diesel shown below.
A piece of tape was cut to the proper length and height for the wide striped area on the loco's hood, then the entire strip was cut, at the proper angle, into alternating black/white/black sections. All of the sections meant to be white were marked with a "W", then
all of the sections were applied to the hood, which had already been airbrushed white. The unmarked sections served to keep the "W" sections parallel, and were removed before the black paint was applied.
Once you have initially applied the tape to the model, sight along the line of the tape - this will show any deviations from a straight line: despite your most careful measurements when cutting the tape, raised details on the model can throw the tape line off. When everything looks satisfactory, use your finger nail or a suitable tool to burnish the tape in place. While the tape
will stretch to allow you to mould it over raised details, you'll have less chance of the tape lifting from these areas while you're painting
if you allow some slack in the tape as you're burnishing. A good way to maintain your straight line during this step is to first apply a temporary strip of tape on the opposite side of the line that you're attempting to mask along - this doesn't need to be burnished, but allows you to burnish the actual masking as you apply it, while still keeping a straight line. Obviously, remove this guide tape before painting.
If you're really worried about colours "bleeding" under the tape, apply a spray, using same colour over which you've applied the tape, along the edge of the newly applied tape, in order to seal it. When that's dry to the touch, apply the new colour, and as soon as it's dry to the touch, remove the masking tape. To do so, use the tip of an X-Acto blade to lift an end of the tape, then pull the tape back over itself at the sharpest angle possible - the sharper the angle, the less chance of lifting the paint under the tape. Even after exercising all of this care, you may find areas that require touch-up. To do so, wait until the paint is
completely dry, then use a good-quality brush and unthinned paint to perform this task.
Wayne
