Explosions arising from contact of molten metal and water can occur in a number of metallurgical processes. Explosions caused by LNG contacting water are also possible. Such explosions are known by several terms such as steam explosions or physical explosions. A recent review discusses aspects of the phenomenon and suggests an initiative to promote cooperation in the area to further the understanding of it. The present paper aims to contribute to this initiative. The main conclusions are: (a) the superheat limit is possibly more accurate as an upper limit to that reached by the colder liquid than other assumptions such as the temperature of the hot liquid; (b) in relating the blast effect to a quantity of TNT, care should be taken to recognize that only a fraction of a TNT explosion enters a shock wave; (c) it is important to distinguish between the energy in the hot fluid and the actual expansion energy of the steam or vapour.