Spark testing is a method of determining the general classification of ferrous materials. Normally it entails taking a piece of metal, usually scrap, and applying it to a grinding wheel in order to observe the sparks emitted. These sparks can be compared to a chart or to sparks from a known test sample to determine the classification. Spark testing also can be used to sort ferrous materials, establishing the difference from one another by noting if the spark is the same or different.
Spark testing is used because it is quick, easy, and inexpensive. Moreover, test samples do not have to be prepared in any way, so often, a piece of scrap is used. The main disadvantage to spark testing is its inability to identify a material positively; if positive identification is required, chemical analysis must be used. The spark comparison method also damages the material being tested, at least slightly.
Spark testing most often is used in tool rooms, machine shops, heat treating shops, and foundries.
