Abstract: A glow discharge unit suitable for making surfaces such as carbon-coated electron microscopy grids and glass cover slips hydrophilic. The use of a vacuum leak detector (Tesla coil) in place of a conventional high voltage power supply and a small plastic desiccator for the vacuum chamber make the unit very inexpensive. Due to the small volume of the chamber and the simplicity of the unit, the whole glow discharge process can be carried out in only 2 to 3 min., a time considerably shorter than that required for conventional vacuum evaporators. The hydrophilic surfaces thus obtained improve adsorption of particles by several orders of magnitude in preparation for negative staining, freeze-drying and other procedures.