There is some good stuff in the archives about this topic (especially Ron Nossaman's comments from Sep 6, 1998), but there is a great scientific paper available that says it all. Everything you ever wanted to know about Silica Gel: http://www.apsnyc.com/pdf/silica_gel_SW_2003.pdf What I learned from this paper: 1. Silica Gel can be used to protect against incoming moisture temporarily, until it takes in all the moisture it can handle. (This will keep your piano strings from getting rusty in the steamship container, if the piano is sealed in a relatively air tight plastic bag.) For this use, the gel is usually dried in an oven at 100 degrees C, so it essentially starts from "zero" moisture content. Once it is full of moisture, it needs to be baked to restore the desiccant properties. (Don't do it in your kitchen oven!). 2. Silica Gel can also be used as a long-term RH buffer, such as in museum display cases. It will adsorb or desorb moisture as the air from outside leaks into the case, keeping the RH relatively constant. To work, the gel needs to be spread 1/4 inch or less deep on a tray for maximum air contact, and there needs to be about 1/2 pound per cubic foot in a tightly sealed case, allowing for about one air exchange per day. (In a piano, we would need to seal all the air leaks, use some sort of impermeable finish on the case and soundboard, and use between 6 and 10 pounds, spread thin on trays to have any significant effect.) >From other 'net surfing on Silica Gel: It is not bio-degradable. It is not particularly hazardous, unless you turn it to dust, which is an iritant. Certain brands add other chemicals to increase effectiveness or provide a color indicator of moisture content, which tend to be more hazardous than the plain-jane stuff. Don't be afraid of it, but don't eat it either. So no, it doesn't have any long term effect on the piano, good or bad. It certainly doesn't respond fast enough or in great enough quantity to do what a Dampp-Chaser does for a piano. ...Unless you can spread 10 pounds of it 1/4 thick on trays in a tightly sealed piano. ;) Greg Graham, RPT in the (currently) damp and chilly Pocono Mountains
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