Nucleate pool boiling characteristics were investigated in a reduced graphene oxide (RGO) colloid with a water base. Critical heat flux (CHF) pool boiling experiments were performed to analyze both the boiling heat transfer and the CHF on a silicon dioxide plate in colloids with concentrations of 0.0001, 0.0005, and 0.0010 wt.%. The RGO colloid was prepared by chemical reduction of hydrazine from graphene oxide, and diluted for the experiments. In the boiling experiments, boiling heat transfer and CHF enhancement were shown to be related to the concentration. Special attention was focused on two phenomena: the enhanced CHF and improved boiling heat transfer in the RGO colloid. Possible mechanisms for these phenomena were examined from various viewpoints, including the RGO coating layer characteristics, wettability, water absorption by the RGO porous medium, and history of the RGO coating layer development. (C) 2014 Elsevier Ltd. All rights reserved.