The electronic Overhauser effect was employed to enhance nuclear magnetic resonance images obtained in a magnetic field of only 16 mT. Despite the weak magnetic field, the technique can reveal, in some systems, various aspects of ionic transport and kinetics apparently not observed in conventional high-field magnetic resonance imaging. We employed Overhauser imaging to monitor the spatial and temporal evolution of the gelation of sodium alginate by calcium ions. The sensitivity of the Overhauser enhancement to small changes in gel composition permits a stringent test of the underlying mechanisms of transport and chemical kinetics.