Electronic circuit production

A method of electrolytic etching and deposition, comprising:

• a. introducing a continuous section of substrate into an electrolyte within a container, wherein the substrate is initially patterned and includes a conductive layer comprising protected areas defined by having a patterned layer of protective material formed thereon and unprotected areas defined by being without a patterned layer of protective material formed thereon;
• b. applying a voltage between a first electrode, in electrical contact with the electrolyte, and a second electrode, physically separated from the first electrode and in electrical contact with the substrate, and thereby removing the unprotected areas of the conductive layer of the substrate by electrolytic etching;
• c. removing the patterned layer of protective material to change the protected areas into further unprotected areas;
• and
• d. at a subsequent time, reversing the polarities of the first electrode, in electrical contact with the electrolyte, and the second electrode, in electrical contact with the substrate, and thereby increasing the thickness of the further unprotected areas of the conductive layer of the substrate by electrolytic deposition.