Q: I am new to powder coating, but the plant where I work has been doing it for a few years. The guys do a good on single color and are starting to experiment with multi-colors.
I’m wondering, is multi-color powder coating possible? If so, do you have any information that would help us?
A: Thanks for the question. One often overlooked characteristic of powder coatings that sets them apart from liquid paint is that they are discreet fine particles that typically stay that way when they are sprayed. Unlike most liquid paints, mixing two powder coating colors doesn’t result in an intermediate color but a blend of individual particles.
For example, mixing a red paint and a yellow one of same technology will yield an orange paint. With powder coatings, you get a unique speckled finish.
So yes, powder coatings can be mixed. There are many scenarios to consider.
1. Physically blending two or more powders will give you a speckled finish. By mixing an orange, medium brown, and a dark brown, you can simulate a rust patina. Blends of large-particle textured powder can give the effect you see on roofing shingles. Mixing a light teal green with a black powder will give you a weathered copper look.
2. Some powders are blends of incompatible materials and result in what are commonly referred to as veins and “hammertone” finishes. The veins are comprised of a dry blend of an incompatible powder and a silver or bronze pigment. Hammertones are best formulated by the powder manufacturer, though you can experiment with blending various common powders with these veins and hammertones to get interesting effects.
3. Metallics and pearlescents. The simplest technique to create a metallic effect is to blend an already made powder coating with a metallic pigment. Aluminum flakes are most commonly used, but you can also try bronze and stainless steel pigments to create fascinating effects. Concentrations of 0.2-5.0% are typical. Pearlescents are specially synthesized flakes that give a shimmering effect. These can be incorporated just like metallic pigments. Variations of pearls include color shifting flakes that appear as one color at a given viewing angle and another color at different angle.
4. Holographic effects. These are one of my favorites. Microscopic flakes that possess a prismatic effect can be added to powders. The most dramatic effects are realized with darker, more vibrant colors. These holographic flakes are rather expensive but produce a rainbow of colors as you change your viewing angle.
5. Applying dry powder onto another dry powder. Gradient color effects can be achieved by applying one color on part of your target and then covering the rest of it with another color. The intersection of the two colors can be quite aesthetically pleasing. Some people have come up with a way to simulate wood grain by spraying multiple dry layers of light and dark brown powders then “combing” the finish before it sees the oven.
One thing to remember, dry blends of various powders yield a variable finish. It is difficult to achieve the exact finish repeatedly. Particle size differences between powders and additives and electrostatic variations in application will produce slightly different looks. And reclaimed oversprayed powder will certainly look significantly different than the original blended powders. Keep this in mind if you are trying to coat large parts or long runs of parts.
I would encourage you to experiment with the possibilities. The effects you can create are endless and only limited by your imagination.