Abstract: A device for solidifying a layer of a liquid that solidifies upon cooling, such as agar, the liquid being contained in a row of petri-dishes or the like. The device utilizes a horizontally rotatable disc for receiving the dishes, a mechanism for supplying dishes to the disc, and a mechanism for removing the dishes, with solidified liquid, from the disc. A cooling mechanism is positioned below the disc to cool the disc and thereby cool the dishes. A mechanism is provided for slowly rotating the disc so that surfaces of materials in the dishes solidify in a non-rippled manner.