Driving around Spokane, you may not see a whole lot of full color backlit signs. That’s because full color outdoor backlit signs present a special challenge: constantly changing ambient light.
In the beginning of sign making, backlit signs were hand painted with translucent paint that looked great when lit from the front by the sun as well as at night when lit from behind. The transition from hand-painting to cut vinyl made the process easier, and translucent vinyl worked well for both day and night settings. The downside to the vinyl was that it was and still is very expensive compared to other options. In addition to a high price tag, the vinyl could only produce spot color, so images and text had to be simple. Photos, gradients and special effects were not possible.
Digital printing has solved both of these problems, but naturally, it leads to some of its own complications. Digitally printing a sign face is more cost effective than either hand-painting or ordering and cutting several colors of translucent vinyl. It also allows for a multitude of nearly unlimited color choices, and digitally printed gradients produce a realistic, vibrant image. The complication arises when different lighting – from the outside by the sun, and from the inside by electrical lighting – hits the print. Backlit signs have to not only look good at night when they’re lit from behind, but they also have to look good all day long when the light source comes from outside. “Traditional digitally printed backlit signs look washed out at night. One option is to bump up saturation, which makes the sign too dark during the day,” Signs for Success owner John Bogensberger explained.
The solution? Over several weeks of testing, we found that the best combination was printing the image in color, then a layer of 50% opacity white ink, and finally another layer of color. These three layers make it possible for the image to shine through no matter what direction the light comes from. “During the day, the white backs up the outer layer, and during the night, the second layer of color comes through due to the backlighting,” John explained. “This allows the sign to look great day or night.”
In the picture above, we printed the same image using three different processes. The image on the right shows a “single strike,” or just one layer of ink. This type of printing is great for most signs, but as you can see, the backlighting washes out the image at night. The image on the left shows the same image printed on the front of the sign face, then printed in reverse on the back side. This “double strike” method gives better color, but can be very difficult to register exactly on both sides. The center image is a “triple strike” with color, white ink, then color printed on the sign face. Our test image is printed with 100% opacity white ink, but by lowering the opacity to 50%, the image is bright and clear.
Even with the extra ink and extra printing time required for a triple strike, this is still the most cost effective option for vibrant full color backlit signs that look great in any lighting conditions. The color will be sure to last at least 3-5 years, and if the sign is laminated, you can expect 5-7 years of life.
We coined the phrase “backlit triple strike” – since perfecting the method, we just don’t do backlit signs any other way. “Triple strike” refers to the three trips the material takes through the printer, first receiving the sign graphics in full color, then a layer of white ink, then another run of the graphics in full color. This technique allows the intended color and saturation to show through whether the light source comes from outside the sign or from within, creating great backlit signs day or night.