Tungsten electrodes were prepared to analyse the plasma geometry at TIG welding. The investigated
electrodes were La02, Th02 alloyed. Tip flatted electrodes were grinded as well. The shape of plasma
were analysed for 36 different electrodes. Analysing of digital pictures, the plasma geometry were
measured. Whole and brightest plasma area was checked as well. Measured values were represented as a
function of taper angles. Main conclusion is that the maximum of the diagrams, which characterise the
effect of taper angle for sharpened electrodes, were at taper angle of 20-30°. The properties of the red
and the black electrodes are running collaterally. Despite of them the characteristics of the gold
electrode shift to higher taper angles causing by the high La02 content of the electrode. There was no
clear correlation between the electrode taper angle and the shape characteristics of plasma for the
electrodes, which were prepared with a flat tip
