  The progressive onset of slip at the wall, which corresponds to a slip length
increasing with the solicitation time before reaching a plateau, has been
investigated for model viscoelastic polymer solutions, allowing one to vary the
longest relaxation time while keeping constant solid - fluid interactions. A
hydrodynamic model based on a Maxwell fluid and the classical Navier's
hypothesis of a linear response for the friction stress at the interface fully
accounts for the data, without any adjustable parameter. No viscoelastic
response needs be postulated for the friction, reflecting the local character
of solid-liquid friction mechanisms.
