(57) The present disclosure relates to mercury containing reed switches and to methods of preparing switch blades for use in such switches. Heretofore such reed switches have been doped with mercury after the reed switch blades have been mounted in the envelope, the mercury migrating to the contact area of the switch blades, made of a mercury-wettable material, after sealing. The present invention avoids the expense and complexity of this procedure by improving the control of mercury dosing to enable improved performance of such reed switches in low power applications, for example in automatic test equipment, process control equipment and data processing terminals. This is achieved by forming a mercury amalgam on the contact area of the switch blades prior to insertion in the glass envelope and subsequent sealing of the switch blades to the glass envelope.