Large Format Printing: Installing Low-Tac Wall Clings

I had a bit of a crisis today installing a large format low-tac wall cling at a movie theater. The problem was that I tried to do it myself. I also learned a lot about low-tac wall clings.

First, some background. I went to the theater without my fiancee to give her a break, assuming the wall cling would be easy to apply. It was a promotional piece for the new movie Ferdinand, a cartoon about a bull. The wall cling was approximately three feet by four feet, printed in four color process inks on clear plastic.

If you looked closely, you could see that the job had been “back-printed,” with the heavy, peel-away backing sheet followed by a layer of low-tac glue, followed by white ink that would be a “ground” layer behind all printed imagery. Then there were the four process colors, and then the thick plastic sheet that would be the covering for the entire wall cling.

Interestingly enough, the 4-color custom printing extended just slightly beyond the perimeter of the white ink. Based on my knowledge of both large format printing and optics I knew exactly why the white ink was there. Not only did it provide a single color backing, regardless of the color of the wall onto which the large format print was mounted, but it also provided a bright, even, reflective surface for the ambient light.

Light projected from a ceiling lamp onto a clear surface (like the clear plastic of the wall cling) goes through the overlaid transparent screens of the process colors and has nothing to bounce off to return to the viewer’s eyes unless you have a white backing. In this case it was a very bright white to enhance the brilliance of the colors comprising the bull, his horns, and the promotional lettering and title of the film.

If you disassemble a lightbox with a back-lit advertisement in a subway station or even at a cosmetics counter in a department store, you’ll see the very same treatment: a white inkjet backing behind the 4-color imagery.

The Problem

To get back to the crisis, it takes four hands to peel this large a wall cling off a backing sheet. I learned this as I was holding the backing sheet steady with my two knees as I peeled the image off in preparation for hanging it. To make a long story short, the weight of the card-stock backing sheet at that large of a dimension (three feet by four feet) pulled and stretched the plastic of the wall cling and caused portions of the image to flop over onto other portions of the image. This happened even when, or especially when, I had attached the top part of the cling to the wall as a starting point.

To back up for a moment, the proper way to install such a large-format print is to peel the top of the image slightly off the backing sheet and attach it to the wall. Then you smooth out the image as you work downwards, peeling the wall cling off the backing as you pull the backing sheet out and away, finally attaching the bottom of the wall cling to the wall. You then use a squeegie, a flat plastic rectangle, to burnish the wall cling to the wall, moving from the center outward. You do this to move the air bubbles out and away from the center, finally affixing the image to the wall in as flat a position as possible.

Keep in mind that this particular image was not rectangular. Now, on large format printing equipment you can set a plotting knife to cut out the image in an irregular way. In this case, the operator had used the digital data to trace the horns of the bull, as well as other parts of the overall graphic, such as the title of the film. This “kiss cutting” went through the plastic sheeting but not through the backing sheet. Therefore, when I pulled the wall cling away from the backing, I had an especially irregular contour cut around the entire image, bull and movie title. Needless to say, all of this plastic covered on the back with glue wanted to cling to itself rather than to the wall.

It was not quite a clump or a ball, but it was scratched up a bit. The adhesive had pulled up some of the inkjet pigment attached to the underside of the plastic sheet (remember that the entire printed image is actually sandwiched between the wall, the adhesive, and the outer clear protective cling material).

The Solution

So I called my fiancee, and she was onsite in less than an hour with acrylic paints, brushes, and a hair dryer. She also had a clear head, presence of mind, and the patience to peel apart the folded over portions of the Ferdinand wall cling without further damage.

Once the wall cling was flat, the two of us could work from the bottom up, attaching it to the wall. We did this for the following reason. The backside of the reclining bull was as close to a straight line as anything else on the large format print graphic. Moving upward and outward to keep the air bubbles toward the outside, we could eventually reach the most irregular portion of the image, the bull’s head and horns, and the movie title. We then burnished the entire image with the plastic squeegie to remove the air bubbles and make sure the Ferdinand cling stuck to the wall.

Finally, my fiancee went up on the ladder with the acrylic paints we use in our art therapy work with the autistic. Using her fingers to mix and apply the colors, she repaired all the cuts and scratches, anywhere the plastic had stuck together and had removed the pigment from the back of the wall cling plastic sheeting. She added this color to the outside of the cling, that is, on the surface of the plastic sheet. The acrylics worked perfectly. They were matte coated (similar enough to the dull coating of the plastic sheet). And they dried quickly. Moreover, by not painting on the underside of the plastic sheet, my fiancee kept the acrylic paint off the movie theater wall.

Then it was over and we were on our way home. I was very grateful. We have one more to install. We will do it together.

What You Can Learn From This Case Study

You can learn a lot about large format signage from static clings and wall clings:

1. 1. Static clings have no adhesive but stay attached to windows based either on static electricity or on the propensity for moisture in the air to attach thin plastic sheets to glass (depending on what you read).

1. 1. Wall clings are large format print graphics that stick to walls or windows with a light form of adhesive that is somewhat repositionable.

1. 1. Window clings tend to be small and manageable by one person on a ladder. Wall clings are not. The glue likes to stick to itself and the plastic sheeting more than the walls. Therefore, you really need two people for installation.

1. 1. Looking carefully at the order in which the glue and pigments have been applied to the plastic sheeting is instructive. From the outside in, you have the matte or satin surface of the outer plastic cover sheet, then you have the four process colors from the inkjet printer, then you have a white base to reflect light back to the viewer, then you have the low-tac adhesive. Then you have the wall. This can teach you about light and vision.

1. 1. Digital information can direct a knife, held in place vertically, much like a plotter pen. The knife can cut almost any shape around the printed graphic, so the background does not need to be rectangular. Presumably, in the not too distant future you will be able to do the same thing with a laser cutting device.

1. Finally, the glue itself is pretty amazing. In spite of my struggles with the adhesive causing the plastic cling to stick to itself, the glue was still rather forgiving. It came apart with patience and time, and then it stuck to the wall perfectly at the end, making for a dramatic and hopefully never-to-be-repeated evening.

This entry was posted on Monday, April 23rd, 2018 at 11:01 am and is filed under Large-Format Printing. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.