The appearance of many a good piano and organ is spoiled by the discoloration of the keys. Where children have played upon them with sticky fingers, merely to wipe them with a clean duster will not always suffice; a moist washleather will be better. The yellowish - green colour of composition keys is mostly due to playing with damp, perspiring hands, this being most strongly marked at about the centre of the keyboard. Much discoloration without corresponding signs of wear can generally be traced to absorption of moisture from the fall or lid; the instrument being kept closed for long intervals the keys are shut up in the dark. It is then advisable to leave the keyboard portion open more, sunlight being a splendid bleach. This applies with equal force to ivory or composition keys. The use of powerful bleaching agents as nitric or sulphurous acids, or salts of lemon, is not advised; there is always a risk of allowing such solutions to flow between the keys on to the woodwork, thus causing the wood to swell and, in some cases, the keys to bind or stick together, resides, most bleaches require several days, sometimes weeks, to be effective. The most that can be advised is to cleanse frequently with benzine or benzoline, which in many cases will restore the colour.

For anything beyond this the keys should be removed from the instrument so that the surface of the coverings may be levelled or the discoloration taken out by the aid of a cabinet-maker's steel scraper and glass-paper. The keys then require to be repolished in accord, ance with the instructions on polishing ivory by the hand method given on p. 251.