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Airwatts vs. CFM

I rcccntly wcnr shopping for shop vacuums. I found that most manufacturers rate shop vacuums in air-watts, not in cfm as with dust collectors. What is an airwatt? Is it related to cfm?

David Banks Milwaukee, WI

O Airwatts measure the energy of air flowing through an opening—just as watts measure the amount of electrical energy moving through a wire.

The airwatt rating is a reliable way to compare the power of different shop vacuums. That's because all manufacturers use the same airwatt test, which measures airflow over a mandatory range of opening sizes. Cfm measures airflow at only one size, which varies from one manufacturer to the next. This makes power comparisons difficult.

An airwatt rating is also a better measure of suction power than cfm—which is appropriate, since shop vacuums should be able to pick up small ofTcuts and stray debris. The suction measurement for dust collectors is usually given as cfm at a specific static pressure.

Susannah Hogcndorn "Q&A" editor

A Bug-Free Finish

®I made a mahogany coffee table, brushed on the last coat of shellac, and left it on the veranda to dry. When I came back later, there were insects stuck in the finish. How can I fix this?

George Whitefield Belize City, Belize

O You're in luck. Shellac, like lacquer, forms a brittle film that you can scrape to remove imperfections. Lightly scrapc the buggy areas clean with a cabinet scraper, then apply another coat of finish.

If you'd used varnish, you would have had a problem. Varnish and its relative, polyurcthanc, form an elastic film that doesn't scrape well. With these, you should carefully pick out any bugs or other debris with a toothpick or fine tweezers while the finish is wet. Once the finish cures, you'll have to do a lot of messy sanding and recoating to remove trapped bugs.

To avoid this in the future, I'd recommend finishing in a clean, enclosed room—or screening in your veranda.

Sandor Nagyszalanczy West Coast editor of AW Santa Cruz, CA

WHERE TO FIND IT Weaving a Hickory Bark Seat, a video from chairmaker Owen Rein, is available for $23.90 (inc luding shipping) from Hickory Bark Video, c/o 13th Floor Productions, 500 Wall St., Ste. 1302, Seattle, WA 98121.

"Hollowood" veneered wood cylinders for furniture legs, kaleidoscopes, and boxes is available in oak, cherry, mahogany, and other woods from BrandNew, 6125 Pedernal Ave., Coleta, CA 93117, (800) 964-8251.

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