How do Humidity Fluctuations Vary for Wooden Artifacts?

Very High Vulnerability
(coating over right angled grain joint or crack)

  • 5% RH change, gradual fatigue fracture
  • 10% RH change, fracture possible each cycle
  • 20% RH change, fracture definite first cycle

High Vulnerability
(veneer over right angled grain joint, lacquer over knot-free wood)

  • 5% RH change, zero fatigue fracture
  • 10% RH change, gradual fatigue fracture or plastic deformation
  • 20% RH change, fracture possible each cycle
  • 40% RH change, fracture definite first cycle

Medium Vulnerability
(wood with little or no coating)

  • 10% RH change, zero fatigue fracture
  • 20% RH change, gradual fatigue fracture or plastic deformation
  • 40% RH change, fracture possible each cycle

Low Vulnerability
(loose wood panels, single component tool handles)

  • 40% RH change, possible accumulation of fatigue fracture or plastic deformation if the freedom to move or the coatings or the slowness of the fluctuation are less than perfect.