Lucky you -- that baby grand piano is your Porsche, an investment in pure pleasure and exquisite design you love to pamper and hand-polish. Protect its gleaming black lacquer with extremely conservative and gentle cleaning -- and keep everything off the piano to avoid even faint scratches that will mar the perfect finish.
First be sure of the finish -- modern pianos are often finished with polyester, not lacquer, so check that yours has a true lacquer finish. Protect the lacquer -- and the general condition of your piano -- by placing it out of direct sunlight, keeping it dusted, monitoring the humidity and temperature in the music room, and situating the instrument to safeguard it from knocks and abrasions. The underlying wood will expand and contract due to temperature and humidity fluctuations, which can prematurely age the finish, cause crazing and cracking, and damage your piano. Sunlight is very hard on the piano's finish and can fade the rich black. Water damage from the condensation on a glass or the dampness or overflow from a plant might result in white rings or more calamitous damage that could bypass cleaning completely and require refinishing. It goes without saying that you should never put any cleaner or moisture inside the piano; the inner workings of a grand piano are the province of professionals.
Dusting a piano, black lacquer or fine wood veneer, is an art form, not to be undertaken lightly. Save cotton flannel or another baby-soft rag for the job. But don't start with rubbing. Dust is abrasive and will scratch the fine finish on the instrument. Remove the dust with a feather duster -- exterior frame only. The guts of the piano are best left to a trained technician. After the light dusting, dampen your super-soft cloth with clean water, wring it out until nearly dry, wipe away remaining dust and immediately wipe away the moisture with a dry cloth. Wipe in the direction of the sheen pattern to preserve the flowing, gleaming lines of the finish. Dust your piano often and consider an air filter to remove air pollution particles in a city or area that gets high traffic. And don't forget to dust the keys -- start with the feather duster; then progress to a damp cloth, followed by a dry cloth. Use separate cloths for the faux ivory keys and the painted black keys to avoid transferring any color, and wipe along the length of the keys.
Baby Your Lacquer
Pianos have two basic finishes: polyester and lacquer. Contemporary pianos favor polyester finishes because they are easy-care and resist scratching. Lacquer takes a little more love. Beyond simple dusting, a lacquered piano with smudges will respond to a very soft cloth, dipped in a solution of water and extremely mild soap, such as Murphy's Oil Soap, and wrung out thoroughly, wiped gently over the finish in long lines of straight strokes. The cloth should be barely damp so it doesn't leave streaks of water on the piano, and you should wipe along the wood grain, if visible, or the finish sheen pattern. Follow this with a water-dampened cloth and then a dry cloth. Satin-finish lacquer, less shiny than semigloss or gloss, doesn't need polish and could turn dull and filmy if you apply any. Polish shinier finishes with a product made specifically for pianos or fine furnishings. Common household furniture polish is for common household items, not baby grand pianos. Use very little polish and wipe the surface clean afterwards with a clean dry soft cloth. It's really best to skip polishing if possible, because you risk damaging the finish or delicate parts of the piano when you apply anything to it. Be absolutely wary of pressing down on edges and corners when dusting, washing or polishing. You can wear away the lacquer and even remove it right down to the raw wood.