The bags of dessicant (usually silica gel) referred to are going to be of very little use in this application. They are ok for inclusion in packaging for an item in transit, but not much else. It's crucial to know whether the conditions that gave rise to the mildew in the first place, have been altered. If not, any cleanup will be only temporary, and the mildew will take hold again in due course. Mildew thrives in damp conditions. Why might a room be damp? Various factors come in to play. One might live in an area with a very humid climate. One might live in an area with a very rainy cool damp climate (like me in the West of Scotland). Ordinary activities in a home generate moisture and put it into the air - moisture from baths, showers, laundry, etc. Simply lying in bed asleep at night, we exhale about 20 fluid ounces of water. Where does this moisture go? The warmer air is, the more moisture it can hold. When warm moisture-laden air finds its way into a cool room in the house, lots of the water in the air will condense out onto surfaces in the room. Thus if there is a "front parlor" that's only occasionally used, and not generally heated, and that's where the piano is, the piano will be a prime target for condensation and mildew. Probably the simplest and most effective way to deal with moist air in a home, is to buy a domestic dehumidifier. These electrical appliances cost pennies a year to run, and very effectively remove water from the air in a home. I speak from personal experience, and I believe that no home in te West of Scotland should be without one! An illustration of how things can change in a home was provided by friends who are also clients of mine. They are accomplished musicisns. Their grand piano is in the Front Room, which is not their usual family/sitting room, and is not kept heated. For many years, they had an open solid fuel fireplace in that room, and no problems. Then, they blocked up the fireplace and fitten an electric heater. All of a sudden the room smelled musty and the piano strings started to rust! Why? Because, previously the open chimney provided an escape route for moisture-laden air floating in from elsewhere in the house, and circulation of air was able to take place. Now, with the fireplace blocked, any moisture-laden air getting into that unheated front room, was shedding its load of moisture by condensing in the room, including the piano. In a cool damp climate, when it's raining outside, opening the window to circulate the air won't help, as the air outisde is much wetter than that inside. The solution for my friends was an electric dehumidifier. 25 years ago, I slept in a bedroom that was getting increasingly mildewed. It was not centrally heated and was on an exposed corner of the building. Electric dehumidiefers were not as well-known back then, and relatively expensive. But I got one; an excellent, whisper-quite little unit, a Toshiba Mini-Dry. In the first 48 hours of its opereation, I measured the water it extracted from that room alone (there was draft-excluder sleaing the door). The little Mini-Dry extracted FIVE QUARTS of water from that room! And that excellent little unit is still going strong today. Anyway, this is just to point out that the conditions in the lady's home need to be assessed and addressed, in order to permanently prevent any recurrence of mildew. Best regards, David Boyce.
This PTG archive page provided courtesy of Moy Piano Service, LLC