Brass wire is one of the crucial components of a bassoon reed. Its placement and how it's put on the cane have a profound effect on the way the finished reed plays. We offer several gauges of wire, and depending on many factors, you may actually want to try a mix of different gauges. You don't need much wire for any single reed, so even a 2oz. spool can provide enough wire for dozens of bassoon reeds.
The gauge for brass wire for bassoon reeds will typically be between 21 and 24 AWG. The higher AWG (American Wire Gauge) number the thinner the wire. Thinner wire will take up less space on the reed and theoretically allow freer vibrations of the reed, especially when used at the first wire position. If, for your reed design, the wire is too thin, it may not support the cane enough, and it can more easily break if you need the wire to be tighter. Heavier gauge wire will be more supportive, but may dampen the vibrations of the blades, especially on the first wire position.
Some reed makers I have spoken with will use all the same gauge wire (I personally use 22 for everything), while others will use thinner wire for the first wire closest to the blade, while using heavier wire for the third and/or second wire. Feel free to experiment and see if you find enough of a difference to use different gauges!
As for where to put the wires, there is no consensus in the reed making community on where the wires should go. The wire placement is largely a component of the reed shape, as the wires create the support structure for the fulcrum of the reed that helps keep the tip open.
Once you've made your reed, adjusting the wires can be a simple way to alter the playing characteristics of the reed.
Happy reed making!