Hardenning is a process that involves several different steps. STIFFENING, which has 10 letters, is the process of making something more rigid and less flexible. FREEZING, with 8 letters, is the process of cooling something to a temperature below its FREEZING point. Petrifying, also with 10 letters, is the process of turning something into stone or a similar substance. Lastly, Ensuring, with 7 letters, is the process of making sure something is secure or safe. All of these processes are part of hardening and are used to make something stronger and more durable.