Abstract: By the welding of plastic material, the plastic material is placed between a welding electrode of a profile and pattern mating the welding to be performed, and a counter electrode comprising one or several pulse heating wires. Together the pulse heating wires cover the pattern of the welding electrode and project preferably a short distance beyond the welding electrode. The pulse heating wires are furthermore mutually and outwardly electrically insulated. A separating tape of a higher melting point than the plastic material has been inserted between the pulse heating wires and the plastic material. The welding press comprises a welding plane with the welding electrode and a fixing plane for the counter electrode. The temperature of the welding electrode can be kept constant and within a temperature range of approximately 20.degree. C. to approximately 250.degree. C. The fixing plane is non-heated. The pulse heating wires are secured to the fixing plane and are mutually and outwardly electrically insulated.