Does anyone here use the Edinburgh etch? I tried it on brass. The first time is was very aggressive. However, on re-using the solution once the bite was much less.

I have been using concentrated Ferric Chloride on its own with generally good and predictable results and re-using the same solution many times without noticeable loss of strength. What is the explanation for the loss of strength with the Edinburgh etch? Does it lose potency with age or with use? Can it be restored by adding more citric acid?