Steel wool experiment. Computer artwork of the equipment needed for the steel wool in vinegar experiment. The steel wool is soaked in vinegar for about a minute. It is then removed from the vinegar, wrapped around the end of a thermometer and placed in a second beaker containing water. A cover is put over the beaker and it is left for about five minutes. During this time the temperature will rise. This is because the protective coating has been removed from the wool by the vinegar and the iron in the steel is rusting. Rusting is an exothermic reaction.