Select an appropriate vessel in which to perform the chromatographic separation. The vessel must be large enough to hold the TLC plates and have a lid or cover. While there are tanks made especially for TLC (below), a tall beaker with a watch glass cover is often sufficient.
Fill the vessel with developing solvent. The solvent level should be low enough that it will not reach the spots on the TLC plate. Do not put the TLC plate into the tank yet.
Cover the tank and let it sit undisturbed to allow the solvent vapors to fill the tank.