By Joe Schuster with permission of PWC: Painting & Wallcovering Contractor
Surface preparation, as any painting contractor will tell you, is perhaps the most important part of any job: get it right, and the coating work is easier; get it wrong, and you may have wasted all the time and money it took to get the coating on the surface.
In most cases, how to clean and prepare a surface is a slam dunk decision.
“I’d say that in 90 percent of our jobs, we’re going to end up using a pretty standard method of surface cleaning and prep,” said Matt Terrell of Atlanta-based Goodman Decorating, which marks 80 years of business this year focusing on commercial and industrial work throughout the southeast and eastern seaboard and as far away as areas of the Caribbean. “For most jobs, it’s a matter of sanding and water.”
That other 10 percent of jobs can provide a challenge, he said.
“There are hundreds of different considerations you have to look at,” he said. “It depends on so many factors and if you make a mistake—if you use the wrong medium or the wrong method—you can end up destroying the substrate. Beyond that, you have to be aware of the environmental effect of anything you do. That’s probably the number one consideration.”
Here, we take a look at a handful of projects that presented some prep or cleaning challenges to contractors and the solution found for each project.
The stone of Trinity Cathedral before and after blast cleaning. Courtesy of Young Restoration Company. |
Contractor Steven Young grew up in Pittsburgh, PA, and for his entire life had admired the now 135-year-old Trinity Cathedral that was the center of the city’s Episcopal Diocese. When he got into the building restoration business in the 1970s, whenever he drove past the church—by that point coated with soot from decades of smoke that poured from the city’s steel mills—he thought: that’s one of the projects I’d like to be involved with.
When the diocese decided to clean and restore the church as it prepared to celebrate its 250th anniversary, Young got his chance.
The job, however, was challenging for a number of reasons.
One, during the cleaning process—which Young estimated would take five months—the cathedral had to remain open for Communion and prayer services. Two, whatever process Young ended up using had to be strong enough to scrub away a century of carbon build-up; but, at the same time, it could not damage the structure, the stone, or the surrounding environment.
Young and the engineers associated with the project conducted experiments over three years using a number of methods, including high pressure water cleaning and hydrofluoric acid. In the end, they settled on using ARMEX, a water-soluble abrasive, manufactured by the ArmaKleen Company.
ARMEX is a fine-powder blasting abrasive made from bicarbonate of soda. It was developed by ArmaKleen in the 1980’s when the Federal government invited the company to demonstrate if it could clean the Statue of Liberty without damaging its metal substrates. The abrasive can be used in a conventional dry blast machine, or it can be combined with water in various wet abrasive blasting systems.
Young finds the product user-friendly.
“It’s extremely cost-effective,” he said. “You don’t have a lot of prep work like masking before you use it because it’s not going to damage the surface or cause other collateral damage—for example, it’s not going to etch the glass adjacent to the stone; and because it’s water-soluble and uses a minimal water stream, it’s completely benign, aside from whatever material you’re using it to remove.”
But it wasn’t a simple matter of opening a box of ARMEX and blasting, Young said. For instance, the stone substrate had differing amounts of soot on different sides of the building. The right elevation, for example, is different from the left because the left elevation is adjacent to another building while the right elevation is not, meaning that the right elevation benefited over the years from some natural cleaning as rain would pelt the elevation, while the left elevation, not as exposed, had a heavier coating of carbon.
Young said “it took a lot of trial and error to find the right method, the right granule, the right pressure, and the right distance from the surface” to clean the variety of substrate conditions. He used a dry abrasive blast machine with a water curtain around the nozzle to suppress the dust. The blast pressure was about 40 psi.
Vacuum-shrouded, dustless sander, similar to grinder used for coating removal in Los Angeles County Jail. Courtesy Dustless Technologies.
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Last year, Larry Ratliff of California-based Pro-Mark Group got a call from the Los Angeles County Sheriff’s Department, which had a paint problem in its jail.
“They have four major compounds that house 60 prisoners each; and in the areas where they have banks of pay phones for the prisoners to use, the walls were a mess,” he said. “While the prisoners were on the phones, they would mark up the walls or pick at the paint and gouge it. To correct the defects in the paint, the sheriff’s department would just keep painting over it to cover it up. In some places, they had 30 to 40 layers of paint.”
Instead of repainting it yet again, the department decided it would just strip all the paint and leave the concrete walls bare.
When the department called Ratliff, he initially thought he’d end up using a chemical stripper; but when he got to the compound, he realized it would not be an effective solution.
“The problem was that chemical strippers take time to work,” he said. “In southern California, environmental regulations prohibit using hot solvents that work quickly, so we’d end up using a product that we’d have to leave on the walls for 24 to 36 hours, and there was a concern that prisoners would remove some of it from the walls and throw it in the face of other prisoners.”
What Ratliff settled on was using a system marketed by Dustless Technologies.
“We decided that the best solution was to grind it off, but because of the environment, we had to be sure that we didn’t produce dust or contamination because we didn’t want any of the prisoners suffering breathing problems and also didn’t want dust flying all over the guys’ beds.”
Dustless Technologies manufactures a line of grinders, sanders, and other power tools that come equipped with vacuum shrouds that prevent the escape of dust created by the tool’s operation. Dust does not slow the engine, nor does the vacuum “cough” dust when the user switches it on or off.
“We were able to grind the paint off a wall measuring 10 feet high by 30 feet long in 30 minutes,” Ratliff said.
Before and after stripping and repainting of floor in animal pen, Brookfield Zoo. Courtesy SufaceTek. |
One of the biggest challenges Drew McCammon of SurfaceTek Inc. faced was removing coatings from animal pens at the world-class Brookfield Zoo in Chicago.
“They were coated with epoxy and the animals were tearing it up with their claws, and some of them were eating the paint chips,” he said. “The Zoo called us and said, ‘You’ve got to get the paint out of here.’”
The Zoo had considered and rejected a number of methods because they were either too time-consuming or presented environmental hazards for the animals or the workers.
Among other products, SurfaceTek—which is a manufacturer as well as a contractor—offers one it calls Super K, a water-soluble, potassium sulphate abrasive used with a blast machine that the company also manufactures.
“Super K is pH neutral so it wouldn’t damage the plantings around the pens and it also wouldn’t pollute the animals’ drinking water or the air,” he said.
For this project, Super K was used in the company’s proprietary dry abrasive blasting machine at 90 to 100 psi blast pressure. A water ring at the nozzle helped to suppress the blast dust.
Don Calvert Painting has a major contract with Questar Corporation to maintain the natural gas giant’s pipelines throughout a several-thousand-square-mile area of the American West. A large part of that work is cleaning corrosion from the giant valve assemblies that are, for miles, the only part of the pipeline visible above ground.
Completed coating work on above-ground component of Questar Corporation pipeline. Courtesy Don Calver Painting.
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In the past, contractors would blast the corrosion with coal or copper slag but that presented problems.
“A lot of the gas lines run between residential properties, or others are along streams or in wetlands,” Calvert said. “If you use slag, you have to contain it or spend a lot of time and money cleaning it up afterwards.”
Calvert settled on a crushed glass abrasive medium produced by Washington-based TriVitro Corporation. The glass can be used with conventional abrasive blasting equipment set on a slightly lower pressure than what is used with other media, in this case 125 psi. TriVitro’s glass abrasive is effective at both cleaning the corrosion and stripping old coating but is also environmentally friendly.
“You can leave it on the ground,” he said.
The TriVitro product does cost a bit more than conventional slag; but, said Calvert, labor costs are lower because he doesn’t have to contain or clean up the medium. So, overall, cost using the glass abrasive are competitive.
Operator uses sponge blasting to clean Bartlett Hall. Courtesy Sponge-Jet Inc. |
When the U.S. Military Academy at West Point decided it wanted to restore Bartlett Hall, the 93-year-old center for its scientific programs, it presented State Construction Services with a number of challenges.
“The granite surface of the building was heavily coated with salt, rust, and efflorescence,” said Krzysztof Grubecki, who owns State Construction. “It would have been easy to clean it with conventional sand blasting or an acid-based chemical, but we couldn’t do that because of environmental reasons.”
Instead, Grubecki tackled the 18-month-long project using a blasting system called Sponge-Jet, the product of a two-decade old company that cleans surfaces using sponge particles, sometimes mixed with other abrasive media, such as garnet.
Grubecki elected Sponge Jet’s white sponge system, which mixes plastic particles with the sponge because, while it would clean the granite, it would have minimal environmental impact.
For one thing, he said, he liked that the system collects and recycles the media it uses. Beyond that, even if someone made a mistake and set the pressure on the blasting unit too high, it would not harm the granite.
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