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State-Of-The-Art Sand Blasting
Jim Deardorff, Chillicothe, Missouri, who has been cleaning and painting old steel for more than 20 years, has discovered a better way to sandblast.
  "Most people use sandblast sand to clean paint and rust off old equipment," he says. "But for antique tractors, classic cars and even vintage airplane parts, I've found that a blend of iron aluminum oxide and ground-up black walnut shells cleans better and more gently than sand. It can be used at lower pressures, doesn't damage fragile parts and is dustless, so parts cleaned with it don't require pre-paint preparation."
  He has a unique way to promote his new sand blasting medium to car and tractor collectors. "I can take all the paint off a pop can without damaging the aluminum," he says. "You can't do that with conventional sand blasting."
  Deardorff discovered his new sandblast mix by accident. "I normally re-use aluminum oxide blasting material. One day as I was re-using some after using it to clean up parts that were sitting on wooden pallets, I noticed the parts I was cleaning with it immediately became bright and shiny. I looked at the material and saw that small bits of wood from the pallets had actually been blasted off and were mixed in with the aluminum oxide," he says.
  "I wondered if the wood had anything to do with how clean and bright the steel looked. I sometimes use ground black walnut shells for cleaning parts in food processing plants or petroleum pipelines where sand might cause problems with bearings, manifolds or pumps, so I mixed some of the walnut shells into the aluminum oxide and the results were even better," he says.
  Deardorff found that this mixture not only cleans up the metal without pitting or scratching it, but it also helps prevent rust. "I've had some customers tell me they've let parts sit for up to a year without any recurrence of rust," he says. "I'm not sure why this is. Perhaps it just does such a good job of cleaning the metal that it's harder for rust to develop on the surface.
  "I've taken parts I've cleaned with this mixture to metallurgists at the University of Missouri-Rolla School of Mining and Engineering for evaluation and am hoping they'll be able to tell me why this happens," he says.
  Using his mixture of walnut shells and aluminum oxide, Deardorff has been able to reduce the amount of pressure needed to clean paint and rust from fragile parts. "I normally use about 35 psi and rarely more than 50 psi to clean with this mixture," he says.
  Deardorff says parts cleaned with his mixture can usually be primed immediately with no further brushing or washing.
  While his mixture is initially more expensive than sand, it can be reused numerous times, limited only by the amount of contaminants that build up in it after each use. "It takes 10 reuses to break even with it," he adds. "And when it can no longer be used for parts cleaning, I use it one more time to brush-blast galvanized steel buildings before repainting. I've found this is much more effective for removal of oxidation (chalking) and rust than power washing. And then, we can paint the same day. With power washing, we have to wait for the siding to dry."
  Using his walnut shell mixture, Deardorff can strip the paint from an entire medium sized tractor in 4 to 6 hours.
  You can use the new mix with any sandblaster but Deardorff recommends a closed-top sandblast pot, which uses vacuum to pull media into the chamber. "This is the only thing I've found that works at low pressure," he says. It allows him to drop the nozzle pressure without losing pressurization of the blasting media. He also uses an air-induction nozzle, which mixes outside air with compressor air and the media. "This increases the air volume, which gives a more uniform blast pattern without reducing media impact speed," he explains. "It will work with as little as 5 psi, which is what I use for cleaning off pop cans."
  Deardorff packages his special blasting mix in 50-lb. bags. It's called Classic BlastÍ. "We hope to have it priced at less than $20 per bag, plus shipping," he says.

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2002 - Volume #26, Issue #3