An extensive experimental study into the relationships between tensiotrace features and surface tension of alcohols and bifunctional liquids has produced a series of empirical relationships. The use of this 'inside the rainbow' studies for pendant drops is known as optical tensiography. A series of empirical relationships discovered will enable the experimental measurement of surface tension without the correction factors that have been used since the development of the drop volume/weight method over a century ago for a restricted range of liquids. This approach offers potentially important applications in surface science and it is also suggested how these new relationships will be tested using theoretical models developed by the authors in the ongoing work. This paper provides the first experimental investigation into the commencement of the tensiotrace, a position at which optical coupling begins, which reveals measurement possibilities.