Saving Old Masters: Yoshi Nishio, Nishio Conservation Studio

Nishio, 54, is originally from Japan, and he worked at the Smithsonian's Freer Gallery and at Boston's Museum of Fine Arts before opening his own studio.

What Nishio does is not restoration. Conservation entails scientific analysis to remain true to the artist's intention.

The Japanese screen, for example, required microscopic analysis to determine which pigments were original and which had been added during a restoration around the turn of the last century. Curators had to decide whether to risk losing some of the original pigment to remove the restorer's paint, which hid the original shape of the grapes and other details. They instead chose to conserve the painting as it was, leaving open the possibility of removing the overpaint sometime in the future with techniques that don't yet exist.

Nishio and his team cleaned the painting with brushes and ultrasonic mist over a suction table that catches any particles of dust and dirt. They repaired flaking and cracked paint, lined the panels with new paper from mulberry trees, replaced the decorative silk edges, and installed a new lacquer frame.

"We give life to the paintings so they can go another 100 to 200 years," Nishio says.

Conservation has become more conservative, adhering to a code of ethics similar to medicine's "first do no harm." Instead of painting over cracks, conservators use pinpoint brushes to fill in the paint.

The process typically takes two months for paintings and three or four for screens. Conservation can cost anywhere from a few thousand dollars to $40,000.

Homeowner tip: "Paintings need vacations," Nishio says. Ultraviolet light is a main cause of deterioration. Nishio recommends periodically taking down paintings and storing them in a place with controlled temperature and humidity.