What is the most common mistake that results in the development of a completely blank piece of film? It has just happened to me for the first time and I cant figure out what went wrong. Holder light leakage? Would that not result in some but not all of the film being clear? Developer exhaustion or weak solution? My stock solution of PYROCAT HD was mixed 17 days ago and I keep it tightly capped and in an ideal location. Any ideas?