Experiments so far indicate that the correct metal ratio to produce brass is n tin and 3n-1 copper. Possibly other recipes exist, but this is the only confirmed one so far.
The maximum ratio possible is 50 tin and 149 copper (that is, where n = 50)
When making brass, doping a reactory at 7:59:35 or later produces maximum output. (145 brass for the above example)