What can I do to escape the perils of dehydration -  Feb 2005


Everybody who’s spent time at Meadowood had heard this song, so we expect you to join in on the chorus... the perils of dehydration. 

  • We sing this song every year because the dehydration damage in instruments is gradual & unnoticeable until it’s well advanced. The unfinished wood on the inside of your instrument absorbs & loses humidity; during the process, the wood swells & shrinks. Small, gradual humidity fluctuations are not a problem; sudden change & prolonged dryness are. 

  • Tone wood used in instruments must age for years in a controlled environment to ensure that the wood resists warping. Then, to prevent wood from changing size & shape while they build instruments, luthiers keep humidity in their workshops controlled near 50%. Even in a complete instrument, swelling &  shrinking of the wood occurs. 

  • Spruce & cedar, used in the tops of acoustic instruments, are softer & weaker than woods used for backs & sides (mahogany, koa, maple, walnut, rosewood...). In addition, the sides, are curved & glued onto bracing that makes them even more rigid. So, when the instrument absorbs moisture (humidity > 60%), the rigid sides hold the edges of the weak top in place, & the swelling top puffs outward a little. While the instrument is swollen, the strings are higher from the fingerboard & the tone of the instrument is slightly muffled. The condition is not damaging to the instrument. 

  • In dry conditions (humidity < 40%), the sides still hold the top in place. Shrinking away from the sides, the top is in tension, and can crack. When humidity drops suddenly below 40% or descends below 40% an extended period of time, the top of your instrument risks cracking. 

  • No one warrantees against cracks caused by lack of humidity. Nope, the repair comes out of your pocket. And, depending on the size, location & character of the crack (or cracks), the repair can be pretty pricey–– sometimes hundreds of dollars. To add insult to injury, the cracks are sometimes difficult to fix & remain visible after repair (especially if the wood has time to distort or collect dirt before repair). 

  • Someone will surely tell you that they've had instruments for years, never humidified, & have had no problems. We celebrate that good fortune, but repair several cracked instruments every winter. We keep humidity at Meadowood at a minimum of 40% & strongly encourage you to do so. The rewards greatly outweigh the effort. 


What can I do?

  • Measure humidity where you store instruments (people find out that their homes are at 20-30% when they measure humidity). Digital hygrometers ($20-$50) are more accurate than analog meters in the same price range. 

  • In humid periods (above 60%) you can improve instruments’ voices and playability if you air-condition, have a qualified repair technician perform seasonal adjustments if action gets high. 

  • In dry periods (below 40%) you can keep instruments away from heaters, use room humidifiers or instrument humidifiers to keep humidity around the instrument above 40%. 

  • Immediately repair cracks to increase the possibility of complete repair that is less visible.