I etch about half a dozen printed circuit boards each year at home, using an aqueous ferric chloride AKA iron(III) chloride etchant solution. As I want to minimize the costs and hassle of buying new and disposing of old etchant, I would like to know what steps can I take for maximizing the amount of boards I can etch with a given amount of etchant. I have no background in chemistry, so any suggestions are appreciated.
I prepare a certain amount of etchant solution at a time, use it until it fails to dissolve copper effectively, and finally transfer it to a waste tank awaiting disposal. Does the batch size affect the amount of circuit boards I can etch with a given amount of ferric chloride?
Is etchant sensitive to light or fluctuating temperatures while in storage?
Is etchant oxygenation beneficial or detrimental? Many vendors of the chemical and several PCB fabrication tutorials clearly state that FeCl3 etchant stores indefinitely if kept in an airtight container. On the other hand commercial PCB etching devices purposefully stir the etchant by blowing air bubbles trough it, oxygenating the solution in the process, seemingly without adverse effects.