The use and development of diagnostics for thermal plasmas is motivated by the industrial importance of thermal plasma applications like welding, cutting or thermal spraying. While the physical fundamentals of plasma diagnostics were introduced decades ago new technologies allow to perform a more detailed analysis of the mentioned applications with increased spatial and temporal resolution, enabling the investigation of complex processes thereby moving the focus from pure plasma to plasma-material diagnostics. An attempt is made to demonstrate current and future possibilities provided by technical progress using "old physics" with the help of few examples. The examples introduced here focus mostly on welding applications and include the use of high-speed cameras for the spectrally resolved analysis of plasma radiation and two-color pyrometry. In addition the use of Thomson scattering in gas metal arc welding is proposed as well as the use of magnetic field measurements for non-intrusive current density measurements.