Homogeneity testing is performed by means of spark emission spectrometry. Tests include multiple measurements on individual samples on various levels of all rods of the whole cast. The standard deviation resulting from all measurements reduced by those eliminated together with their respective material as outlayers expressed as % of the element concentration is used as the measure for the homogeneity of
these elements. Depending on the concentration of the element, these relative standard deviations are typically found to be between 0.3 - 1 % for alloying and other elements and around 0.5 - 5 % for trace elements.