 Philco used a patented process of applying two tiny electrochemical jet streams of liquid indium sulfate (electrolyte solution) on opposite sides of a thin strip of N-type germanium base material.This process would etch away and form circular well depressions on each side of the N-type germanium base material, until the germanium base material was ultra thin and having a thickness of approximately a few ten-thousandths of an inch.After the etching process was finished, the polarity applied to the electrolyte was reversed, resulting in metallic indium being electroplated into these etched circular well depressions, forming the transistor's emitter and collector electrodes.