  We study the dynamic coarsening of wrinkles in an elastic sheet that is
compressed while lying on a thin layer of viscous liquid. When the ends of the
sheet are instantaneously brought together by a small distance, viscous
resistance initially prevents the sheet from adopting a globally buckled shape.
Instead, the sheet accommodates the compression by wrinkling. Previous scaling
arguments suggested that a balance between the sheet's bending stiffness and
viscous effects lead to a wrinkle wavelength $\lambda$ that increases with time
$t$ according to $\lambda\propto t^{1/6}$. We show that taking proper account
of the compression constraint leads to a logarithmic correction of this result,
$\lambda\propto (t/\log t)^{1/6}$. This correction is significant over
experimentally observable time spans, and leads us to reassess previously
published experimental data.
