The forced ignition experiments conducted in a novel high pressure hydrothermal spallation drilling pilot plant with a Ni/Cr-60/15 coiled wire are presented here. A water-ethanol mixture is used as fuel and gaseous oxygen as oxidation agent. The ignition characteristics of the combustible mixture are analyzed at 260 bar and for temperatures crossing its pseudo-critical point. The influence of the bulk temperature, the fuel composition and the flow conditions on the forced ignition is shown. The properties variation of trans-critical fluids led to results, which seemed counter-intuitive because some mixtures ignited at lower surface temperatures even though they were at lower bulk temperatures than others. These physical, heat transfer mechanisms behind these phenomena are qualitatively outlined. Temperature values between 500 degrees C and 850 degrees C and electrical power values between 60 W and 300 W were measured. (C) 2013 The Combustion Institute. All rights reserved.