This article describes a comprehensive experimental analysis that defines typical fluidization characteristic curve for Geldart's classification groups. Geldart defined four types of materials which differ by the cohesion forces between particles. An experimental apparatus containing fluidized beds of four pipe diameters and fully controlled by LabVIEW was used to perform the fluidization tests. All tests were performed automatically by gradually increasing the air velocity and measuring the pressure drop over the bed. For each test, the fluidization curve was recorded and the minimum fluidization, bubbling, and slugging velocities were defined. It was found that the fluidization curve of material define accurately the Geldart's group to which the material belongs. In addition, was reviewed the reason for those materials and under which conditions the pressure drop increases in the slugging state. Finally, the influence of height to bed diameter H/D ratio on the shape of characterization curve was found. The present study has significant interest for researchers and designers since it enables to predict the fluidization characteristics of two-phase (fluid-solids) flows.