What is Viscosity? What is Rheology? What makes a fluid Newtonian, Thixotropic or Dilatant? To some, the science of viscosity can be a confusing and frustrating experience - if you don't know the basics. In this section, we've tried to answer some of the questions our new - and even our seasoned customers - have asked us over the years….in concise, easy-to-understand language.