Maintaining grain bed integrity during sparge.

I have read some on this, and I am not 100% sure I understand. Why do we "maintain grain bed integrity" during a sparge? I would think you would want to mix the bed to avoid channel forming and ensure no area of the grain bed is neglected. I understand this could lead to an increased risk of a stuck sparge, but I imagine you gain an increased efficiency. Currently I do a semi-fly sparge, pouring approx. 1.5liters of sparge water over the grain bed (I protect the integrity using aluminum foil with holes punched in it) at a time, let it drain and repeat. This will normally get my 75% +/- 3% efficiency.

So I am wondering why would we not mix the grain bed during a fly sparge? Say, sparge with 1/2gal, mix, sparge, mix, etc. etc. Just curious. Thanks


-Kyle

The way continuous sparging works and yields very high efficiency when done correctly is that a linear sugar concentration gradient is maintained. The principals of diffusion are at play in any horizontal slice in the grain bed. Just as that "slice" begins to reach equilibrium, it's lowered down into the grain below where there is more sugar to diffuse in and so it goes.

Most large system lauter tuns do scrape the top few inches the entire time to avoid channeling but you don't want to disturb the 95% layer below.

The way you're doing it, it's closer to a batch sparge only less efficient because you're not stirring the whole thing. IMHO, either fly or batch sparge.

If you stir during the run off you will get grains/husks in the kettle.
One would have to recirc. to set the grain bed every time after you stir it up.
Batch sparing that's the way it's done. But if fly sparging you would have keep
stopping the run off to recirc.