With decreasing pressure, vesicularity increases from a few percent just below the nucleation pressure ( V  = 2.6 vol% at P_F  = 59.7 MPa in the 1,000 kPa/s series) up to 69 vol% at P_F  ≈ 20.5 MPa (Table  1 ; Fig.  4 ).

This observation is in agreement with textural measurements: the vesicularities at P_F  ≤ 40–50 MPa approach equilibrium values in the two decompression series, and are even slightly larger and closer to equilibrium in the 1,000 kPa/s series (Table  1 ; Fig.  4 ).

This conclusion holds as well at 1,000 kPa/s since we measured Δ X  = 0.1 wt% at P_F  = 50 MPa and the vesicularities in the 1,000 kPa/s series (at P_F  ≤ 40 MPa) are equal to those at 27.8 kPa/s or even slightly larger and closer to the equilibrium values (Fig.  4 ).