A system for applying an inorganic coating material to a surface (110) comprising: a spray nozzle unit (50), having the following features:a first end portion (51) with a first connection (11) for a first supply hose (10), for supplying a first component of the coating material, a second end portion (52) for discharging the coating material from the spray nozzle unit (50), a connection unit (60) for mixing and transporting components of the coating material from the first end portion (51) to the second end portion (52), wherein the connection unit (60) comprises a mixing chamber (61) with at least one further connection (21,31) for supplying a second component of the coating material, and wherein at least one electronic sensor (70) is mounted on the connection unit (60), to detect an oscillation amplitude (81) arising at the connection unit (60), a data processing unit (80), a comparison unit (90), a control unit (100), wherein the control unit (100) generates a warning signal (101) when the control data (91) lie above a predetermined limit value, and/or -varies the volume flow (102) of at least one of the components of the coating material depending on the control data (91) is generated by the comparison unit (90). As well as methods for applying an organic coating material obtained by mixing a plurality of components in a spray nozzle unit (50).