Hydrodynamic experiments in cylindrical geometry are used to study both mix (compressible, in convergent geometry) and mode coupling (impact of short wavelengths on long). For both types of experiments, knowledge of the initial conditions (the surface roughness spectrum, amplitude versus wavelength, as well as all target metrology) is very important. This paper is a discussion of the techniques and efforts to document and understand our initial conditions and their uncertainties and how well we can control them.