Preliminary Observations . . . Microscale Changes in Cell Structure At Softwood Surfaces During Weathering

When weathering checks occur within a tracheid wall, the long axis of the checks is diagonal to the long axis of the tracheid, and the checks are believed to follow the fibril angle of the S2 layer. When bordered pits are present, the checks usually pass through them. Weathering checks between adjacent walls of neighboring tracheids are parallel to the long axis of the tracheids and appear to occur in or close to the middle lamella. Weathering checks can strain commonly used paints and varnishes to failure. Checking under weathered varnish at bordered pits in the radial walls of springwood tracheids was noted before any weathering checks were observed in summerwood.

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