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What Do Volcanos and Pipe Organs Have In Common?
Not much, but the May 18, 1980 eruption of Mount St. Helens in Oregon had Northwest pipe organ owners concerned...

From The Console magazine (V18, No. 7, July 1980, pp1-3)
Written by Beverli Davis
With repeated eruptions of Mt. St. Helens and the possible threatening eruption of Mt. Hood, it's not hard to wonder what both the short and long-range effects of the ash and sulfur dioxide will be on the pipe organs of the affected area.
After seeing pictures of, and reading about the destruction and possible harmful effects, it dawned on me that the pipe organs of the area could be adversely affected and that owners need to be aware of the possible effects and to inspect their organs for signs of damage. It could be quite severe in some instances.
Ash particles are what is left of the underground molten magma after a violent eruption, such as that of Mount St. Helens. Ash particles have the consistency of a gritty-fine-powder with sharp edges, much like loose graphite; can stay suspended in the air to easily be sucked-in by an organ blower; and seem to ease through even the tiniest of cracks to settle on everything, including the inside parts of a pipe organ's mechanism to clog moving parts in close proximity such as tracker joints (when dry, a light coating of ash may lubricate like graphite, but if it becomes heavy or damp, it will clog), magnet armatures, pitman valves, and near spots where it could cause short circuits. This could mean trouble and cause ciphers galore.
The best way to keep ash particles out of an organ is to keep the blower off, swell shutters closed, and place filters and blankets over any blower and air conditioning intakes after an eruption until the ash particles have settled out of the air. However, as particles settle they cling tenaciously and it is difficult to vacuum them out of an organ's mechanism. Ash deposit, a day or even an hour immediately after an eruption can probably coat the insides of blowers, regulators and windchests as much as 30 or 40 years of soot from coal-burning furnaces.
Molten Magma contains gasses suspended in it which cause the volcanic explosion when they expand. These combine with moisture in the air to form microscopic droplets which condense onto everything and are absorbed into the skin, building surfaces, organ leather, etc. Sometimes these gasses are inert, but most [are] corrosive such as salt, sulfuric acid, hydrogen chloride, or even arsenic. When these droplets get into organ leather, felts or wood they could speed deterioration faster and force replacement much sooner than under normal conditions.
Since the droplet-concentration level parallels the ash-concentration levels fairly closely, keeping the blower off, swell shades closed and covering any air intakes should keeO [sp] most of the ash and droplets out; but a little always manages to get into the action anyway. The best way to determine what long-range effects will be is to periodically inspect interior surfaces, the action and especially leather and felt for signs of ash-buildup, or deterioration. Prompt removal of such residue will prolong the life of organ parts.

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