A simple glass-coated, fire-polished tungsten electrode with conductance adjustment using hydrofluoridic acid.

A method is described to produce glass-coated tungsten microelectrodes in 4 simple steps: (1) etching of the wire, (2) coating with glass, (3) fire-polishing, and (4) reopening with hydrofluoric acid to adjust the conductance to a final value. Continuous conductance control is provided during the reopening process by means of an admittance meter to guarantee an exact final adjustment of the conductance required. The complete process yields electrodes of high reliability within a few minutes and the quality of the electrodes remains largely unaffected by any of the manufacturing parameters involved, so that high-performance electrodes are produced without sophisticated procedures. The electrodes have been tested successfully over several years recording from cells in the striate visual pathway of the cat.