Under extreme conditions hydrocarbons are known to demix, forming diamond and a hydrogen-rich phase. Here, the authors probe the timescale of this process as a function of pressure and composition. Various hydrocarbon samples were compressed to between 20 and 80 GPa in diamond anvil cells prior to serial x-ray free electron laser heating and time-resolved diffraction. They find that carbon-rich precursors form diamond in 10s of microseconds over the whole pressure range, while hydrogen rich ones take longer. [Image credit: Greg Stewart/SLAC National Accelerator Laboratory]