© 2020, The Minerals, Metals & Materials Society. In situ observation of solidification in a high-temperature laser-scanning confocal microscope is hampered by meniscus formation. In order to overcome this impediment, we developed a concentric solidification experimental technique to study the progress of the peritectic phase transition in Fe–C alloys and steels. We create a small, stable, floating, liquid, and pool within a thin disc-shaped specimen, supported by a solid rim. We then follow the progress of solidification and the subsequent phase transitions as a function of cooling rate. Solidification occurs within a steep temperature gradient and in order to quantify, and model, the progress of solidification, we measured experimentally the exact temperature at the liquid–solid interface. In order to verify that observations on the surface are representative of bulk behaviour, we introduced a differential thermal analysis technique, by which we proved that our in situ observations are indeed representative of bulk behaviour.