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Premask is the pressure-sensitive tape used to transfer a cut graphic from its release liner to the substrate or to protect a given surface. The release liner, also called the carrier, backing or backing paper, is the portion of the pressure-sensitive construction that protects the film’s adhesive before it is applied.

Premask is applied to the front of the vinyl before applying the vinyl to the substrate and aids in successful production, handling and protection of the graphic during installation. Premask typically comes in the form of self-wound specialized paper or plastic with adhesive on one side.

“Application tape or pre-mask is an essential tool to doing a professional application, particularly nowadays where most graphics are not just a simple line of copy,” says Nathan Franzblau, founder of the Professional Decal Application Association, an association of independent certified installation companies based in Jacksonville, Fla.

“If you were going to do a wrap on the side of a vehicle where you have a picture of the beach and there are continuous panels, then you almost have to use the pre-mask to hold it rigid so that you can do your match points between panels.”

Installing with premask
So, listen up, practicing vehicle wrappers, before you install the vinyl you need to put the premask over it. Generally it is not necessary to use premask on a film that is four mils thick or thicker, or for any film that has an overlaminate film applied.

However, a premask does prevent stretching and protects the graphic during handling and squeegeeing. With vehicle wrapping, premask is just a fact of life.

Of course, premask comes in various tacks and no one premask will not fit every type of vinyl. What’s a vinyl installer to do? You need to select a premask with enough adhesion to lift the film from the liner but without so much adhesion that you lift the vinyl back off the application surface. Your best bet is to test the premask for adequate tack to lift the vinyl from the liner. Tack is the ability of pressure-sensitive film or premask to stick to a substrate instantly with nominal pressure or contact time.

Avoiding premask mistakes
One of the biggest mistakes installers make with premask is using too low of a tack, according to Julio Burgos, a product specialist for Oracal, a vinyl manufacturer in Jacksonville, Fla.

“A lot of people will buy medium tack tape because it makes it easier to peel on and off,” he says, “but in actuality some vinyls require a higher tack tape so you end up with more headaches then anything else.”

“Application tape, or premask, keeps everything in position,” says Molly Waters, a spokesperson for Avery’s technical marketing department. “So when you are working with letters and you pull the pre-mask off the liner, then the letters are all where they are supposed to be.

“Premask is an absolute must for sign makers installing vinyl letters,” she continues. “If you apply vinyl without a premask and you use a squeegee that doesn’t have a cloth wrapped around it, then you will scratch the graphic.”

Steady pressure wins the race
Experts recommend using steady pressure while applying premask. You can choose either a squeegee or a roll laminator to ensure smooth and even pressure.

When you are ready to pull the vinyl away from the premask, be sure to grasp the edge of the liner and hold the premask down with one hand. Experts also recommend squeegeeing on the reverse side (the back of the liner) and pulling the release liner away with the application tape side down.

It is important to note that four-color process printed decals may require heat lamination to prevent tunneling of the premask. Tunneling is a condition, attributed to mechanical stress, in which the bond between a pressure sensitive film and its liner or substrate is not strong enough to hold the film in place, which causes it to delaminate and pucker.

“You have to cover the whole graphic with the premask,” Franzblau says. “You make a sandwich out of the decal. So you have what’s known as a backing sheet, you have the vinyl in the middle, and then you have a premask on the front.”

The finishing touches
Some vinyl manufacturers recommend that you allow a premasked graphic to dwell for a minimum of three hours before applying the finished graphic to ensure optimum results.

“From an application standpoint, when you are using a pre-mask you need to wait a little while before you pull that pre-mask off because the adhesive hasn’t had time to bite into the substrate,” says Waters. “If you don’t wait long enough, then as soon as you go to pull the pre-mask off you can pull the graphic back up and create bubbles.”

(For more information on bubbles, read our article "Avoiding Bubbles and Wrinkles")

After applying the premask, avoid exposing the graphic to sunlight except during application. Ultraviolet rays from the sun can cause the tape to prematurely bond to the film, which could leave you with the sticky mess you set out to avoid when you decided to use premask in the first place. Happy masking!