Lamy ink is generally regarded as reliable, but is in experience somewhat thinner than Pelikan or Montblanc. Reports of failing ink flow, where the converter has to be turned a little, are known with some fountain pen / feed combinations; Pelikan 4001 generally does not show such behaviour. Different ink brands should not be mixed, since chemical reactions and flocculation can occur. Comparative measurements of viscosity and surface tension of common branded inks provide insight.