What is Preinfusion?
If you own an Expobar Brewtus IV-R, then you can brew shots of espresso using line pressure pre-infusion while plumbing, and also using Expobar's custom E61 pre-infusion chamber. Pre-infusion is what allows a small amount of water through first, before beginning the shot. It allows this water to saturate the coffee and get the grounds equally wet. This can make the coffee extract more smoothly. Water will always take the path of least resistance. By letting the water saturate the grinds before brewing at 9 bars of pressure, this can help prevent channeling.