Lenfest Plaza, created by the Pennsylvania Academy of the Fine Arts from a half-block of Cherry Street west of Broad, can be a cheerless place at this time of year.

Not much sunlight can penetrate the breezy defile, squeezed between the Academy's Furness landmark and the taller Hamilton building. Perhaps spring and summer will soften the ambience.

For now, two pieces of public art animate the plaza somewhat. At the Broad Street end, Claes Oldenburg's giant paintbrush, which serves as a signpost for the school and museum, adds a touch of color and whimsy.

At the opposite end, Jordan Griska's Grumman Greenhouse delivers a dramatic dose of novelty and social consciousness.

The giant paintbrush is an obvious cliche, but executed with typical flair. Oldenburg is a master of ennobling utilitarian objects beyond the banal through scale and humor, if only slightly.

With Paintbrush, he achieved this by loading the bristle end with orange pigment, then configuring the tip to suggest forward movement, as if a stroke toward a canvas had been arrested in midair.

He also dropped a blob of "pigment" on the sidewalk, although the hues don't quite match. The brush is unequivocally orange, while the blob, which skateboarders have already defaced, shades toward scarlet.

The orange brush tip lights up at night; in daylight, it doesn't stand out as much from a distance as I expected it would. Eventually, like Oldenburg's Clothespin, it should mature into a landmark.

Grumman Greenhouse, a more elaborate undertaking and conceptually more layered, is also less permanent. The first of what is expected to be a series of plaza installations, it will remain in place until late next year.

Artists used to talk about using "found objects," then about "recycling"; the current buzzword for spinning straw into gold is "repurposing." On the plaza, Griska, a 2008 Academy graduate, has repurposed with a vengeance.

His "greenhouse" is a Navy warplane, a 45-foot-long twin-engine Tracker II, built by the Grumman Corp. as a submarine hunter.

Griska bought the surplus plane on eBay for, he says, about $300,000 and converted it to a tiny greenhouse, while keeping the plane's original insignia.

He bent the forward fuselage and lopped off one of the wings so the plane could stand more or less on its nose, the most practical position for the narrow site.

Inside, where the crew and the bombs used to sit, he installed racks for plants that grow under lights. The plants - vegetables, herbs and flowers - are provided by the Pennsylvania Horticultural Society, which uses the edible bits for a program that feeds low-income families.

Given the diminutive size of the "greenhouse," this isn't exactly a loaves-and-fishes operation, but it creates a cozy backstory.

At its heart, though, Grumman Greenhouse reframes another familiar biblical parable, swords-into-plowshares, but with a humanitarian gloss. Griska would like viewers to ponder the history of the plane, its first "repurposing" to civilian use by the California department of forestry, and now its second reincarnation as an objet d'art.

Perhaps a few people will do just that, in warmer weather. Yet a single perambulation of the plane, which appears to have dropped from the sky, delivers its full effect. It's of minimal interest as a sculpture, but at least it's sturdy enough to bear the burden of its pedigree and the artist's lofty expectations.

Felted lunacy. Tristin Lowe's white-felt moon sculpture in the Perelman building at the Philadelphia Museum of Art is an even more familiar object, but thankfully he presents it without elaborate context. One makes of it what one chooses.

Like the huge sperm whale that Lowe showed at the Fabric Workshop and Museum several years ago, his intensely pocked and cratered moon is shaped by an inflated bladder; a slight flattening of the base gives away the fact that it's hollow.

Lunacy is fashioned from 14 segments of felt, its handsewn surface laboriously teased and picked to create the craters. A bank of lights illuminates one side, a neon sculpture of blue-purple tubing the other - like direct sunlight and earth glow.

Like Griska's greenhouse, Lowe's moon represents an immense amount of labor. Yet unlike the more demonstrative and polemical plane, the moon inspires contemplation. And, placed off-center in an otherwise empty gallery, it's serenely beautiful.

We have learned a lot about our moon in the last half-century, yet it retains its essential mystery. If you see both sculptures, I'm guessing that the moon's image may stick in your mind long after the repurposed sub-killer has faded to black.

Dutch precision. As a kind of entr'acte between Rembrandt and an equally marketable Van Gogh exhibition that will open Feb. 1, the Art Museum has put up a petite show called "Dutch Treat" that provides a window into Dutch society during that country's Golden Age.

The exhibition is built around 10 small paintings by Gerrit Dou (pronounced Dow), Rembrandt's first and perhaps his most influential pupil. Dou's meticulously detailed genre scenes, often slyly symbolic and moralistic, were popular not only during his time, the 17th century, but well into the 19th, and made him one of Holland's most financially successful painters.

The Art Museum show, which includes work by some of Dou's noted contemporaries such as Adriaen van Ostade, Paulus Potter, and Jan Steen, offers a splendid chance to savor the pleasures of what the Dutch called "fine painting."

Dou was a master of methodical precision, which he executed in small scale - most of the paintings aren't any larger that a sheet of typing paper, and some are smaller. At this scale, viewers must focus and concentrate in a way they might not with bravura brushwork on larger canvases.

Dou's images are domestic and homely - a cat lazing on a window ledge, a girl with a parakeet, a praying hermit, a herring seller instructing a boy in her trade, and two old men conversing.

The most fascinating picture depicts a goat before a fantastical greenish landscape, perhaps an admonition against the perils of lust, which the goat represents.

Despite Dou's association with Rembrandt, his art, especially a naturalistic self-portrait, doesn't resemble that of his master in any way. In relationships between art teacher and pupil, that should be the ideal.

Art: A Touch of Lunacy

Tristin Lowe's moon sculpture is on view in the Perelman building of the Philadelphia Museum of Art through Jan. 29. The Gerrit Dou paintings continue in the main building through Jan. 1.

Hours are 10 a.m. to 5 p.m. Tuesdays through Sundays and to 8:45 p.m. Fridays for the main building, 10 to 5 Tuesdays through Saturdays and 11 to 5 Sundays for Perelman. Admission to both buildings is $16 general, $14 for visitors 65 and older, and $12 for students with I.D. and visitors 13 through 18. Prices for Perelman only are $8, $7, and $6, respectively.

Information: 215-763-8100 or www.philamuseum.org.

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Contact contributing art critic Edward J. Sozanski at 215-854-5595 or esozanski@phillynews.com. Read his recent work at http://go.philly.com/ edwardsozanski.