depending on the application (chemical components being separated, and the required operating temperature) and the scale of the process (from very few microliters to process scales involving many liters), different types of condensers and means of cooling are used. alongside the temperature differential and heat capacities of the cooling fluids (such as air, water, aqueous organic cosolvents), the size of the cooling surface and the way in which gas (vapor) and condensing liquid states come into contact are critical in the choice or design of a condenser system. since at least the 19th century, scientists have sought creative designs to maximize the surface area of vapor-liquid contact and heat exchange. many types of laboratory condensers—simpler liebig and allihn, coiled graham types, simple and dimroth types of cold finger condensers, etc.—now common, have evolved to meet the practical need of larger cooling surfaces and controlled boiling and condensation in various procedures involving distillation, and a further very wide array of materials for packing simpler condensers to increase surface area (such as glass, ceramic, and metal beads, rings, wool) have been studied and applied.