Permeable polymeric monolithic materials are prepared in a plastic column casing. In one embodiment, the permeable polymeric monolithic materials are polymerized by the application of heat from an external source starting at a low temperature such as 40 degrees centigrade, depending on the mixture and size of the column, and continuing at a higher temperature, such as 60 degrees centigrade. The temperature at the start of the polymerization is low enough so as not to cause exothermal run-away conditions and to avoid high heat of reaction that would prevent a substantially constant temperature across the cross-section of the column. The higher temperature is used after sufficient monomer depletion has occurred and steric interference has increased so the polymerization reaction is sufficiently slow to avoid heat of reaction generation high enough to cause significant reduction in the homogeneousness of the pore sizes.