Doming

Lately, our customer-service and sales representatives have been fielding numerous questions about doming. "What is doming?" "What materials can be domed?" "Can you dome printed vinyl?" "What type of doming resin should you buy?" And, finally, "How do you do it?"

This two-part article will provide answers to such questions, so you can decide whether doming is suitable for your business, and, if it is, should you attempt doming in-house or subcontract?

Doming is the process of adding a glass-like, plastic-resin bubble to a 2-D surface, which transforms it into an eye-catching, 3-D product. For a small, additional price, you can simulate the appearance of a vacuum-formed or molded part, without having to purchase expensive tooling and production equipment.

Vinyl isn’t the only material you can dome. Just about anything that isn’t porous — metalized polyester, metals, and such plastics as acrylic and polycarbonate — will work. (Note: Anything that’s porous can absorb moisture from the air and cause bubbles to form in the doming liquid. I’ll discuss bubbles later.)

Recently, one of our United Kingdom-based customers showed me some samples of his work — an award plaque and some prototype signs. In each example, doming resin had been applied over metalized-vinyl films. The resin bubble acts as a lens and magnifies the film’s brilliant, light-diffracting effects, creating a very elegant appearance. Even with standard opaque vinyl, doming makes something ordinary appear extraordinary.

Because it’s so cool looking, doming has inspired numerous, creative signmakers. The most important question, though, is what doming can do for your business, not what you can do with doming. Doming is simply another way you can differentiate your company from the competition. By converting standard vinyl graphics into rich-looking signs, you can command higher selling prices and add to your profit margins — that’s the meaning of value-added.

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Resins

Resins typically fall into one of three classes of materials: epoxy, UV-curable resin and polyurethane. Within each classification, several products are available. For outdoor applications, most signmakers, and companies that specialize in doming, choose polyurethane. After comparing each material’s performance characteristics, you’ll see why polyurethane is the best choice.

Epoxy resins are popular for doming such advertising applications as key tags, badges and plaques. Available as one- or two-part systems, epoxies are inexpensive and easier to use than other materials. Because epoxies cure slowly, air bubbles trapped in the resin often rise to the surface and disappear, forming a bubble-free finish.

Unlike polyurethane resin, epoxy doesn’t react with humidity in the air. Thus, you can work with it without having to run your air conditioner or dehumidifier. In addition, epoxy resins are user friendly and cure at room temperature.

Because sunlight yellows the clear, plastic material, epoxy resins aren’t suitable for outdoor use. Plus, due to their softness, epoxy resins can be easily scratched.

Next are UV-curable resins, which fall into two classes: low- and high-intensity. Although low-intensity doming liquids cure when exposed to black light, others require high-intensity, UV-curing units.

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UV resins work similarly to UV-ink systems. Exposure to UV light initiates a photochemical reaction that quickly hardens the liquid. In contrast, other resin types require hours, and sometimes days, to fully cure.

UV resins are ready-to-use, one-part systems — no measuring, no mixing and no bubbles. Plus, they’re relatively safe to use.

Unlike one-part systems, two-part epoxy and polyurethane components must be mixed, which often generates bothersome little bubbles that usually end up in the dispensed doming liquid.

In the future, UV-curable resins might be suitable for high-volume production shops, but not signshops. Here’s why: Low-intensity, UV-curable resins harden after being exposed to a black light (the same type of black light common to the ’60s and ’70s hippie era). Further, low-cure resins don’t withstand prolonged outdoor exposure — after six months in the sun, they begin to yellow. As UV exposure continues, these resins cure and harden until they become brittle and crack.

High-intensity, UV-curable resins cure in approximately 15 seconds, after having been exposed to a special light source that costs thousands of dollars. Thus, unless you specialize in high-volume production, these systems aren’t for you.

Most signmakers and screen-printers I know use two-part polyurethane systems comprising a resin and an isocyanate curing agent that hardens the doming liquid. Although working with polyurethane resins is typically burdensome, such resins can withstand outdoor rigors. Because they resist yellowing, polyurethane resins are suitable for vinyl graphics and other signage applications, including OEM decorative emblems, nameplates and labels.

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In addition, the material remains flexible and doesn’t crack, craze or flake. Polyurethane resins not only weather well, but they also block UV light and, in turn, protect the material they cover. This means the base vinyl and printed image will survive longer outdoors.

Earlier this year, I visited the Q Panel testing labs in southern Florida to examine vinyl graphics that had undergone accelerated weathering equivalent to three years of outdoor exposure. The screenprinted and domed graphics panels looked like new.

However, as wonderful as polyurethane resins are, they have one major drawback — they’re hygroscopic. They suck up moisture like a sponge. Any moisture absorbed by the doming liquid reacts with the resin and forms tiny bubbles of carbon-dioxide gas. Thus, to minimize bubble formation, you must control your shop’s humidity.

Safety tips

Before using doming liquid, read the kit’s instructions and the OSHA Material Safety Data Sheet. Because doming liquid can unexpectedly spurt out of the dispensing nozzle, wear safety goggles. If you get some resin in your eyes, immediately flush them out with water and seek medical attention.

To avoid skin irritation, wear the rubber, surgical gloves included with the doming kit; however, never rub your eyes with the gloves. Further, keep food and drinks out of the work area, and don’t smoke. Finally, when you’re finished working with the material, thoroughly wash your hands with soap and water. Am I starting to sound like your mother yet?

Doming liquid can emit small amounts of slightly toxic vapors, including trace amounts of hydrogen cyanide and mercury vapor. In most cases, this doesn’t pose a problem. However, if you breathe enough of these fumes over an extended time period, you could damage your lungs. Thus, if you do a lot of doming, ensure your work area is properly ventilated. After all, it’s better to be safe than sorry.