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Kate Bachman Kate Bachman
Contributing Editor

Finishing Well

July 25, 2025
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Finish line. Fast finish. Finish first. Finish well. A lasting finish. 

Metal finishing has advanced in myriad ways that abbreviate the time to completion, and improve coverage, adhesion and final quality. Whether a component has been powder- or liquid-coated to imbibe a color and protect, anodized to a certain shade of sheen, deburred to enable safe handling, sanded to a specified smoothness, or doused in a rust preventive, the final stage of a part puts the lid on the box.

Finishing a fabricated component or assembly inscribes a signature. It speaks, “All done here.” 

Finishing Marvel

Chicago, host of FABTECH 2025, which includes the Finishing pavilion, also hosts one of the world’s most extraordinary finishing-technique marvels: Millennium Park’s Cloud Gate, or “The Bean” as it’s affectionately referred to. Cloud Gate, designed by artist Anish Kapoor, assumes the shape of an omphalus, which in and of itself is a design and metal-fabrication marvel. However, it is the seamless mirror finish, intended to resemble liquid mercury, that epitomizes the apex of excellence in metal finishing.

Two decades ago, I interviewed the company tasked with fabricating the 110-ton, 66-ft.-long by 33-ft.-high stainless-steel sculpture: Performance Structures Inc. (PSI), Oakland, CA. I also talked with MTH, Villa Park, IL, the contractor tasked with reassembling, welding, grinding and finishing the landmark piece to that seamless, mirror finish to reflect the city around it—and the people under it. 

Achieving that seamlessness was a labor of love and a finishing feat.

Finishing a Labor of Love

One could hardly guess by looking at the placid surface of the monumental stainless-steel sculpture how much metal and mettle lie below its surface. Sealed within Cloud Gate are the stories—5-plus yr. in the making—of more than 100 metal fabricators, cutters, welders, finishers, engineers, technicians, ironworkers, erectors and managers.

Many worked overtime, performed shop work in the middle of the night, camped out onsite and toiled in 110-deg. temperatures in full Tyvek suits and half-mask respirators. Some worked in gravity-defying positions, suspended from harnesses while holding tools, changing belts and working on slippery slopes. All went above and beyond so that the impossible could be made possible.

Finishing and polishing Cloud Gate’s welds to achieve a seamless appearance was one of the toughest aspects of the onsite erecting and assembly.

“The goal was to eliminate the visibility of the seams,” said Lou Cerny, VP engineering and the MTH project manager. “It’s fully exposed under the brightest of lights available—the full sun at high noon. People can walk up to it from every possible angle.” 

Weld finishing was a 12-step process, explained Cerny when I spoke with him, beginning with rough grinding the weld close to the existing surface using 60-grit zirconium paper on a circular belt. To grind material out of the joint so it would blend with the surrounding areas without gouging, all subsequent sanding was done with semiautomatic belt sanders with wheels that would “ride” the material outside of the joint. The wheels featured adjusting screws so that operators could set the height or depth of the belt until everything was blended to the same level of finish, Cerny relayed. 

From there, the finishers used a special grade of 400-grit ceramic sandpaper, called Type CF-Trizact. “It’s something you don’t really see in our industry; it’s usually for a surgical instrument,” Cerny said. 

It involved a lot of trial and error, Cerny told me. “You’re grinding and polishing welds on a curved surface, and on relatively thin stainless steel, which is very unforgiving. You can’t attack it too aggressively, because if you gouge it, you get a ripple in it or you burn through.”

Avoiding distortion while polishing the welds was difficult as well, Cerny said. “That mirror-finish surface is very susceptible to looking like a funhouse mirror if it isn’t exactly flush. You could start out with a weld seam only about ½-in.wide and end up with an area 18 to 20 in. wide, blending that joint. There could not be any abrupt changes in the surface.” 

To achieve the final, gleaming, highly polished and reflective mirror finish, the finishers used a kind of jewelers’ polish, a waxy substance called a rouge. 

For both PSI and MTH, the Cloud Gate project consumed more time and energy than budgeted. “I think we reached the point where we were committed to it, so we had to finish it,” Cerny said. 

Finishing at FABTECH

While at FABTECH 2025, be sure to discover the newest finishing innovations exhibited there in all of its forms.  Finishing technology has advanced in the equipment, sanding media, prewash, deburring, powders and other technologies that abbreviate the time to completion, and improve coverage, adhesion and final quality. You can read about some of them in the article, “Advancements in Finishing Technology On Display at FABTECH.”

After all, a fabricated metal part or assembly isn’t complete ’til it’s finished. And it just may be a work of art. MF

Industry-Related Terms: Color, Gouge, Grinding, Polishing, Stainless Steel, Surface, Assembly, Welding
View Glossary of Metalforming Terms

Technologies: Finishing

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