Getting Good Coverage in a Shader Coat

Tweaking the material flow and concentration in the wide fan pattern helps solve a problem of inconsistent coverage. August 16, 2012

This project had us spraying a very subtle thin white shader over the pigmented base to create an artificial transparent highlight that then got topcoated with a pearlescent clear. The fan pattern was wide and the hand speed fast and the fluid flow choked to create a dusting. Check out the upper left drawer and you will see a mottled or waffled pattern (somewhat mitigated by Scotchbrite feathering) rather than an even fade. We're wondering if the regulator wasn't passing air evenly (feeding a Sata H1000B) or if the pattern was caused by air interference (bounce back) in that the gun was aimed straight in at the surface. Looking to avoid this in the future!

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Forum Responses
(Finishing Forum)
From contributor R:
Low material flow into a wide fan pattern created this effect. You are trying to distribute a small number of droplets over a wide fan area - think of an inkjet printer and dots per square inch (DPI). The greater the DPI, the better the resolution. Increase the reduction in your shader and then open up the fluid valve some more. Try moving a little slower. Spray a test pattern on a piece of black melamine to fine tune your adjustments and hand speed. The particle size of your pigment will eventually be your limiting factor. If you are using colorants like the 844s, consider using micro-grind pigments like Arti or other brands. For colors other than white, use dyes in your shaders.

From the original questioner:
Thank you. Thinner and wetter has us on a much better track. And reducing the concentration of white in the shader (very little to begin with) makes it easier to slow down without fear of going opaque with it. We've used dye shaders and toners often and never had this issue, but in review, never starved or rushed them.