After transferring the media slurry into the open column, the piston is quickly mounted in a way that avoids air entry, and the column is sealed.

Then the mobile phase is pumped either at constant pressure or at a constant flow, through the column. This causes suspended particles to be packed more quickly and uniformly than gravity settling, reducing the tendency for larger particles to settle first.

After the stabilisation of the bed height, the piston is adjusted accordingly.