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Vinyl Application Over Rivets Made Easy
By Jim Hingst
Note: The following story is the complete, unabridged version of the “Hingst’s Sign Post” column appearing in the July 2006 issue of Sign Builder Illustrated.
Applying vinyl graphics onto vehicle surfaces with rivets is challenging for most sign makers. Vinyl failures to these surfaces are all too common and usually result either because the wrong vinyl was employed for the job, the substrate was not cleaned properly, or the incorrect installation technique was used.
In this feature, I’ll cover some procedures used by professional decal installers that are designed to make these demanding applications easier and more trouble-free. If you take the time to master these techniques, graphics applications will take less time (which will allow you to make more money). You’ll also experience fewer problems, which equates to less aggravating and costly rework—as well as improved customer satisfaction and the possibility of repeat business.
Choose a Film With a Repositionable Adhesive
In the summer, when temperatures are high, adhesives will flow out more readily; this makes the graphics stickier. Often the adhesive sticks before any pressure is applied; once the graphic sticks, you are usually stuck. This condition is referred to as “pre-adhesion.” Trying to reposition the film after it pre-adheres frequently results in distorting or damaging the graphic.
Like or not, under no circumstances are wet applications acceptable when applying vinyl to surfaces with rivets. Application fluid will seep underneath the rivet heads. With no place to go, the trapped moisture underneath rivet heads will seep back out and prevent good film adhesion. This usually results in “tenting” of the film around the rivet. Over time, film that does not properly conform to the rivets will become brittle and will chip away.
If application fluid is “verboten,” using a vinyl film with a repositionable adhesive is your best choice. Unlike the standard films with aggressive adhesives that can be a nightmare to apply, the repositionable films allow the installer to move or reposition the graphic on the substrate, until pressure is applied. Some of the repositionable adhesive systems on the market today include low initial tack adhesives, encapsulated adhesives, and embossed adhesives.
When selecting a vinyl, consider that the application temperature range for the different films will vary. Because the low initial tack adhesives tend to be harder and flow out less readily, they are less tacky. With a less tacky adhesive, graphics are easier to apply in the hot weather. These low initial tack films may not have enough tack, however, to stick to cold surfaces in the winter.
Choose a Conformable Film
As any accomplished cook will tell you, the recipe for success starts with good ingredients. The same holds true for vinyl application. Select a film that is easy to work with and conformable.
For applications to vehicle substrates with rivets, corrugations, or compound curves, you need a flexible vinyl film that will conform to the surface. For these demanding applications, you can’t go wrong using a high-quality cast vinyl.
Cast films start out a liquid, which resembles paint. This liquid (called an organosol) contains pigments, PVC resins, solvents, and additives. It also features a heavy, stable plasticizing oil. Throughout its life, the film retains the weightier oil, which keeps the film flexible. Its flexibility allows the film to conform easily to the heads of rivets.
In making the film, the paint-like liquid is coated onto a casting sheet and baked to convert the film from a liquid to a solid. In this manufacturing process, the cast film is subjected to very little mechanical stress, which contributes to the dimensional stability of the vinyl. What this means: Cast films shrink very little.
Some purists believe that only cast films should be used for vehicle applications; however, cast vinyl isn’t the only high-performance film available. At 2.4-mils thin, today’s high-performance calendered vinyl films are nearly as thin as a 2-mil cast vinyl. Many of these films also have an exceptional gloss level, which equals or exceeds the gloss level of cast films. With an improved polymeric plasticizer system, these films are conformable enough for applications over rivets and corrugations.
Years ago, I never would have thought of applying a calendered film to a surface with rivets. Earlier generations of calendered vinyls were prone to shrinkage and would become brittle and crack as the film aged. The technology involved in making calendered films, however, has changed.
Although the differences among the various categories can be confusing, the use of high-performance, calendered films has grown as a cost-effective alternative to cast vinyl films, especially outside of the United States. For a wide range of signage applications, high-performance calendered films can satisfy a sign maker’s needs.
Use a Heavyweight Application Tape
Premium-grade application tapes are 1-mil thicker than standard-grade application tapes. That little bit of extra paper can make a big difference in your shop and on the job site.
When laminating application tape to graphics, you are less likely to trap bubbles and form wrinkles with the thicker premium tape. This may not seem like a big deal, but it is. If you get wrinkles and bubbles in the tape, you are likely to end up with wrinkles and bubbles in the vinyl. To prove my point, just remove the release from the graphic and look at the adhesive side of the film. You will see where the bubbles and wrinkles are already starting to form. In the installation process, you will often transfer these imperfections to the applied graphics.
When installing vinyl outdoors, a gust of strong wind can turn a sheet of graphics into a sail. If this happens, the heavyweight premium tape is less likely to tear. The standard weight paper frequently tears, which results in trashed graphics.
When working in windy conditions, graphics can also get out of hand and stick together. If you are unlucky enough for this to happen, the heavier tape can save the day; it allows you to more easily pull the graphics apart and salvage the job. (In the squeegeeing process, the added thickness of the premium tape gives extra body to flimsier films, so it’s less likely that you will form wrinkles and bubbles, especially when applying vinyl over rivet heads.)
Following an application, the heavyweight tapes remove more easily in one sheet from the graphics, instead of coming off in little bits and pieces. The cheaper standard grade tapes tear more easily when it is removed, which can slow an installation down tremendously.
Practice
Surely you have heard the axiom: “Practice makes perfect.” This rule especially applies to vinyl application. By attending workshops and watching videos, you can learn the right way to install vinyl over rivets.
That’s just half of the equation. As Confucius is purported to have said: “If you hear, you forget; if you see, you remember. But you only understand, if you do.” Once you have learned professional techniques, you need to practice, practice, practice, in order to produce professional results.
Vehicle Survey
Before you commit to a job, know what you are getting into. Conducting a vehicle survey will help you spot conditions ahead of time that could cause vinyl failures.
In your inspection of the vehicle, note the condition of the substrate. Check for rust, peeling, or chalking paint, as well as surface damage requiring repair. By recommending corrections, you’ll distinguish yourself as a professional rather than just another shop that prints vinyl graphics. Also look for obstructions on the surface—such as locking bars, mirrors, windows, louvered vents, and rub rails—that could complicate the installation and check for old vinyl graphics that will need to be removed.
If the vehicle substrate will be painted just prior to installation, find out when the vehicle will be painted, what type of paint system will be used, and how long it will take for the paint to cure. Curing times vary from one paint system to another and are affected by the environment. A polyurethane paint usually takes three days to completely cure under normal conditions. During winter, however, that same system could require weeks to completely outgas.
Planning
Performing an application in an indoor facility is generally preferable to being at the mercy of the elements. In the bidding phase of the job, make arrangements to secure shop facilities. If your customer doesn’t have a shop where you can work, you may need to rent space.
If you’re performing a graphics installation in the winter, tractors and trailers should be clean the day prior to the installation and pulled indoors the night before so the vehicle has time to warm up. If snow and ice have accumulated on the roofs of the trailers, it should be cleaned off the units before being pulled indoors. This will prevent melting snow from dripping on you and the graphics as you work.
Once trucks or trailers are pulled into the shop, the doors of the units should be opened to allow the cold air to escape. If the shop is inadequately heated, portable heaters can be placed inside the units to aid in warming the vehicle surface. Just be careful with the heaters so you don’t cause a fire.
Vinyl applications in hot weather are even more challenging. As the temperature rises, the adhesive becomes stickier and more difficult to work with.
Since you cannot change the weather, you need to work around it. When I was in the fleet graphics business, I would sell during the day and install graphics after the temperature had cooled off a bit (either in the evening or early morning hours).
Surface Preparation
When scheduling a job, make arrangements for the vehicle to be washed the day before the application. This allows enough time for any moisture under the rivet heads and panel seams to dry completely.
Simply washing the trailers won’t remove all of the surface contamination. On the day of the installation, remove any residual tar, soot, or grease with a cleaner, such as DuPont’s™ 3919S PrepSol.
Finish by wiping down the trailer with isopropyl alcohol. Use a two-fisted approach here: In one hand, you should have a rag saturated with alcohol to wipe down the surface and, in the other, a lint-free paper towel to dry the surface before the solvent evaporates.
Merely wiping the surface with alcohol just moves the dirt from one area to another.
After prepping the surface, moisture may still remain underneath the rivet heads and panel seams. By passing the flame of a propane torch over these areas, any residual moisture will evaporate and any dirt trapped under the rivets will be expelled as the water boils away.
Of course, there are exceptions, such as unpainted aluminum and stainless steel trailers, plastic clad doors, and chalked paint. Each of these requires special cleaning, which I’ll be covering in a future column.
Installation Procedure
1. Job layout. Before starting an application, you’ll need to layout the job. After carefully studying the installation print, tape all of the graphics sections in place to ensure that all of the pieces fit. If the graphics are too large for the surface of the vehicle, you’ll have to adjust the layout. When you make these changes, be sure to record them on the print, so you can maintain the integrity of the design from one unit to another.
Make certain that the bodyline you are using as a reference point is level. If you’re going to be applying graphics to a trailer, measure from the bottom rail of the unit. The tops of some trailers are sloped (which can throw your measurements off).
When installing graphic panels that will overlap, any vertical seams should be “wind lapped” (the front panel overlapping the rear one). When attaching vertical panels, start the application at the rear of the vehicle and work to the front.
If graphic panels have horizontal overlaps, the panels must be “rain lapped” (the top section overlapping the bottom one). When panels overlap horizontally, apply the bottom section first then install the top panel. Each overlap should measure between 1/4-inch and 1/2-inch.
2. Using tape hinges. When installing small- and medium-sized graphics, a tape hinge is generally unnecessary; however a tape hinge can aid the application of large graphics.
To make a center hinge, apply several pieces of two-inch masking tape over the pre-masked graphics. After removing the liner from one-half of the graphic, cut the liner near the hinge. Beginning close to the center hinge, squeegee one side of the graphic then remove the tape hinge and the remaining liner paper. Complete the application, starting with a squeegee stroke that overlaps the first stroke of the application.
A top tape hinge will aid in applying large letters. To create a top hinge, apply a couple of pieces of masking tape along the top edge of the pre-masked graphic. Using scissors, cut between each of the letters and install each section separately, starting at the top of each letter.
3. Remove the release liner. There’s a right way and a wrong way to transfer vinyl graphics from the release liner. The wrong way is to use the application tape to pull the vinyl off the liner. The right way is way is to peel the liner away from the vinyl, exposing the adhesive. If you’re installing a large panel, it would be prudent to remove a little of the liner at a time as you squeegee the graphic.
4. Squeegee the graphics. To squeegee most graphics, begin in the middle of the graphic with a center stroke that divides the graphic into two halves. This initial stroke should serve as your centerline, with all subsequent strokes working away from this line.
Use firm strokes in the application process. Remember, you’re applying a pressure-sensitive film, and it’s called “pressure-sensitive” for a reason. You need pressure to get the adhesive to flow out on the surface.
As you’re making a pushing stroke, your thumb should be at the bottom of the squeegee. As you pull the squeegee, your fingers should be at the top of the tool. Each stroke must overlap the previous one. As you overlap the strokes, angle the squeegee slightly away from the centerline, as if you are forcing the air out from underneath the vinyl.
The angle of the squeegee in relation to the substrate is critical. The squeegee shouldn’t be in a perpendicular position; instead it should be held at a shallow angle, close to the application surface. Squeegeeing vinyl onto a surface with rivets is not much more different than squeegeeing film onto a flat surface. The only difference is that the middle of the squeegee should pass directly over the rivets.
5. Repositioning the graphic. If you encounter a problem when installing graphics (such as a wrinkle or bubble), you’ll need to reposition the film. The repositioning technique involves snapping the graphic from the substrate with a quick, jerking motion.
In repositioning the graphic, don’t make the mistake of slowly pulling the film from the surface—this will only distort the film. (If you do stretch the vinyl, not all hope is lost. By carefully heating the film with your industrial heat gun, the material might shrink back to its original shape.)
6. Cutting the vinyl along the panel seams. Before removing the application tape from the graphic, be sure to cut the film at the edges of the panel seams and then use the edge of your squeegee to tuck the film into the panel seam. The graphics must be cut, or the vinyl will eventually tear at the seams (as the panels flex with the movement of the trailer).
Graphics being applied to roll-up doors must also be cut at the seams. In trimming the film at these seams, double-cut the vinyl at a 45-degree angle along both edges of the joining door panels. Graphics trimmed at the edges of the panels must be edge-sealed to prevent edge lift.
7. Removing the application tape. Remove the application tape by carefully pulling it 180 degrees against itself. If the application tape isn’t easily removing from the vinyl, you can expedite the process by spraying the backside of a paper tape with application fluid. The fluid will penetrate the paper and soften the adhesive, allowing the tape to release more quickly. Of course, this trick won’t work with plastic application films.
8. Puncture the film around the rivet heads. Using an air-release tool or pin, puncture the vinyl in several places around the rivet heads. The holes will allow the air to escape as you burnish the graphic around the rivet.
A multi-pin air-release tool will puncture the film in many places in one motion. Never use a knife to puncture the film; the blade will create a slash in the vinyl that will open up over time. The hole of a pinprick, however, will close around itself.
9. Burnishing the film around the rivets. Installers employ either a squeegee or a rivet brush to burnish a vinyl film around rivet heads. Using a rivet brush is a three-step process: The first step is to brush the large bubble around the rivet head with a firm, back-and-forth horizontal stroke. Brushing the rivets with short, choppy strokes will compress the large bubbles into much smaller bubbles.
The second step is to adhere the vinyl with an industrial heat gun or a propane torch. Heat is important because it softens the vinyl, letting it conform to the irregular shapes of the corrugations and rivet heads; it also breaks the “memory” of cast vinyl films (preventing tenting around rivet heads) and softens the adhesive (making it flow and creating a long-lasting bond).
The final step is to use a rivet brush in a circular motion to burnish the vinyl around the rivet heads. As you brush the rivets, rotate your wrist so the bristles are angled at 45-degrees to the edge of the rivet head.
10. Resqueegee all graphic edges. After removing the application tape, squeegee the entire graphic again using a squeegee covered with a low-friction sleeve. The low-friction sleeve prevents the squeegee from scratching the bare vinyl. This particular step prevents edge lifting and ensures good adhesion.
11. Inspect your job. Before you pack up, always inspect your work to make sure that the vinyl conforms tightly to rivets and that there’s no lifting of the film at the edges.
12. Edge sealing. Some films, such as reflective sheeting, should be edge-sealed to prevent edge lift. The lead edge of a graphic and film applied to roll-up doors should also be sealed with either a commercial edge sealer or a screen print clear coat. Using a fine-tipped brush, paint the sealer with a 1/4-inch stroke, half on the vinyl and half on the substrate. (It’s important to never use varnish as a substitute. The hot solvents in the varnish can penetrate the film and attack the adhesive.)
13. Clean up. When the job is done, remember what your momma repeatedly told you: “Pick up your mess!”
Jim Hingst is Business Development Manager for R Tape Corporation in South Plainfield, New Jersey.
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