Before wood restoration begins, ask the contractor what is in the hopper. Silica sand has caused silicosis for decades, and NIOSH has urged a ban on blasting media with more than 1 percent free silica since 1974. Safe substitutes exist, but each has trade-offs. Get the media name and its safety data sheet in writing.
Rule out silica first in wood restoration
NIOSH's advice since 1974 is to prohibit silica sand, along with any blasting material holding over 1 percent free silica. Britain restricted silica sand in blasting in 1949, and the European Economic Community followed in 1966. The agency's own summary says many sandblasters still contract the disease.
The Australian state of Victoria has banned any material above 1 percent crystalline silica for blasting since 2002. Its regulator rules out silica sand as well as sand from rivers, beaches and white-sand pits. A job in New Mexico has no reason to use any of them.
A crew that says it uses plain sand should get a second question. Ask for the label on the bag.
Why does a 1974 recommendation still matter? Because the habit survives in the word. Many people call all abrasive blasting sandblasting, and a customer who asks for sandblasting may get exactly that. Use the term abrasive blasting in your request, and name the media you expect to see.
Do not assume a substitute is harmless
NIOSH tested silica sand and ten substitutes in a controlled lab, and the results surprise people. Crushed glass produced the highest personal respirable dust concentration, while treated coal slag produced the lowest. Crushed glass is also a common pick for wood, so the result deserves attention.
Cost surprised the investigators too. Silica sand has the lowest price per ton of abrasive but the highest cost per square foot of steel cleaned, about $3.60, while olivine ran about $2.60. The test used steel, not wood, so the dollar figures will not carry over. The lesson does. Price per ton is a poor guide to price per job.
Victoria's regulator lists metal slag among its alternatives but warns that some contains high levels of lead and chromium. Shell media such as walnut and corn cob were not on NIOSH's test list, so its data says nothing about them either way.
Remember the coating becomes dust
The abrasive is only half the dust. The compliance publisher J. J. Keller notes that both the abrasive and the old finish break into fine pieces, and the dust includes particles small enough to inhale. A NIOSH description adds that the material removed by blasting is often very hazardous.
On an old building that can mean lead, which is why a paint test comes first on any pre-1978 house. J. J. Keller also warns that blasting dust can sometimes be flammable or explosive, which is one more reason to ask about containment and cleanup.
Look at the operator's gear
A safety training summary describes the usual protection. It names a NIOSH-certified Type CE blasting airline respirator with a positive-pressure helmet, and notes that powered air-purifying respirators are not recommended for abrasive blasting. It also says OSHA suggests swapping in a less toxic medium and feeding it with water to hold down dust.
I would not hire a crew for wood restoration that blasts in a paper mask. Ask what the operator wears, where the air comes from and what happens to the dust when the job ends. Ask, too, how the crew keeps neighbors and pets out of the work area.
Works when, breaks when
Asking about media for wood restoration works when you can read a safety data sheet and compare it with what is printed on the bag. It breaks when the crew brings several media to the site and changes between them without telling you. Put the media name in the written estimate.
The usual mistake is buying on price and learning about the dust afterward. A cheap job that sends fine dust across a yard can cost more in cleanup and bad feeling than a careful one. Ask who owns the cleanup. A crew that vacuums the work area and bags the debris leaves less to track into the house than one that sweeps and leaves.
Put the media and the respirator in the estimate
Before you sign for wood restoration, ask for three lines in the estimate. One names the media. One names the respirator the operator wears. One describes how dust is contained and cleaned. A contractor who can fill in those lines in a minute has done this before. One who cannot will need time, and that tells you what you need to know. Keep the estimate with those lines filled in. If a problem comes up later, it is the record of what was promised.
Frequently Asked Questions
Q: Is sandblasting with sand legal? A: NIOSH recommends prohibiting silica sand but the sources I read do not say it is banned across the United States. Victoria in Australia bans it. Ask any contractor to confirm what is in the hopper.
Q: What is the safest media for wood? A: None of the sources here rank media for wood by safety. Shell media are common for wood but were not in NIOSH's lab test. Ask for the safety data sheet and a test patch.
Q: Does water reduce blasting dust? A: A training summary says OSHA favors a less toxic medium fed with water to limit dust. Wet methods can leave wood damp, so check moisture before finishing.
Q: What should I do while blasting is under way? A: Keep children, pets and neighbors away from the work area and close windows on the dust side. Ask the crew where the clean zone ends. Check the yard afterward for dust and debris.
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