How many biscuits should I use per foot of wood?
Michael Dresdner: Two per foot will be more than enough for aligning a linear glue joint.
Rob Johnstone: Powdermilk or baking powder? As Michael indicates above, the benefit of biscuits is that they help you align the edge glue joint with ease. Two biscuits per foot is a great rule of thumb, but the goal is just to make the alignment task easier. So, if you have a couple of edges that are 24″ in length and are dead straight & perhaps you would only need two biscuits to do the job.