> if I remember correctly this blue staining of the copper can be
> caused by ammonia in the air. Was the workshop near the countryside? Dung
> is a fine producer of ammonia (resulting in acid rain).
>
Ammonia is basic, and counteracts the effects of acid rain. Acid rain
comes from burning sulfer containing compounds (in coal and oil)
producing sulfer dioxide and then sulfuric acid. Ammonia in the soil and
air will raise the ph.
Howard Etkind
Etkindh@ucunix.san.uc.edu