There are several different techniques now used by parking sign manufacturers. Parking signs are ruthlessly exposed to the elements and the printing method must be selected based on durability expectations.
UV Ink jet
This technique is employed by many banner printers that also print parking signs. It leaves a rougher finish on aluminum. Sign colors are achieved through “spraying down” a mixture of primary banner colors that, when mixed, attempt to achieve a color that matches Federal parking sign standards. Unfortunately, most MUTCD colors are hard to match. Moreover UV ink jet printed parking signs are not particularly durable nor are they abrasion resistant.
Solvent Ink Jet Printing
This is another digital printing technique that has emerged as a favorite for many sign shops. A wide format ink jet printer is the workhouse for many local sign franchises. Solvent Ink Jet printers are commonly used to make truck and van graphics, posters, billboards and banners. Different from the ink jet printers you may have at home, these industrial-grade ink jet printers use solvent-based pigments and not water-based dyes. Pigments are far more durable outside (versus dyes). With a larger molecular size, solvent-based ink jet printers need a larger nozzle aperture, vigilance against clogging, and, often, a longer cure time. This form of ink jet printing must be done on a specially coated flexible label material. To increase durability, the ink jet printed label is usually laminated with another top label made from a clear film.
For parking signs, this label material is then stuck onto an aluminum sign blank. The resulting sign is not long-lasting and vulnerable to “label pick-off”. But, ink jet printing is acceptable for short term, temporary parking signs.
This is a technique employed by manufacturers of green roadway signs. Individual reflective letters, numbers or emblems are applied to a solid reflective base that, in turn, is laminated to aluminum. For parking signs, this technique is often used for one-of-a-kind custom parking signs, such as those that are used for a particular employee’s reserved parking spot.
Individual letters made from thicker reflective aluminum (with a backing adhesive) are made on a router. For thinner vinyl letters applied directly to the rigid parking sign base, a vinyl cutter is the preferred method for cutting out the letters. Parking signs made from applied letters can be exceptionally durable – as long as compatible and approved films are used throughout. Lower cost vinyl lettering, which are often found, is limited by the durability of the vinyl itself – typically, 3-5 years. The other downside to custom parking signs made from applied lettering is the danger of “pick off”.
3M Authorized Printing
The most common printing technique for parking signs uses proprietary and licensed 3M inks. By controlling the printing process (typically using screen printing), the parking sign manufacturer can avail themselves of the 3M warranty that, in turn, is passed onto end users.
Almost all official parking signs are printed using one of the 3M licensed or authorized techniques.
This printing method gives the most durable signs with the most authentic color fidelity. Although 3M’s warranties vary from 7 years to 15 years, in practice, most 3M authorized signs are still legible for many years past this warranty period.
Other sign printing techniques include both thermal transfer printing, laser printing and dye sublimation. Generally used to print labels, all of these techniques can be used for signs. Using a smaller press they are typically restricted to certain narrow formats.