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The hourglass system
Most manufacturers recommend this system.
This hourglass detail allows materials to move
properly and enhances the physical properties of
the sealant. By maintaining this typical detail,
you will avoid cohesive and adhesive failures.
Cohesive failure
Sealant material applied
too thickly will result in
cohesive failure.
When the sealant is so
thick that it cannot
elongate
when
the
substrate is experiencing
expansion, it literally
rips itself apart, usually
in the middle of the
joint, when the substrate
separates.