Originally Posted by Rbeckett
........ My thought is that since the fine powders that create stuck sparges would be flushed from the manifold and possibly even floated to the top it might potentially improve efficiency and prevent a stuck sparge. Any body ever tried this or have any empirical evidence to support this as a good or bad idea?
If you mill properly there shouldn't be much fine powders left after the mash. People are always concerned about grinding too fine and making lots of flour. This is really only an issue when mashing in as a fine grind is more prone to forming dough balls. However once mashed in the flour (starch) is converted to sugars. So the only fine particles that should be left at the end of the mash are the remnants of the husks and the acrospire (tiny barely shoot). Now if you are getting lots of fine husk particles in your grind then you need to re-evaluate your grind.
Let me first state that attempting a sparge on a mash that isn't at least mostly converted can result in a stuck sparge due to starch particles. Many stuck sparges though are the result of lots of proteins and sticky dextrins gumming up the husk bits. I'm a batch sparger, so the rest is in reference to that process, not fly sparging. This is the process I only do for grain bills with high wheat, rye or protein. I have found that the cure for a stuck sparge is of course prevention, and the simplest way I have found around that is to just add more water prior to your first drain.
My normal procedure is after heating to a mash out, I vorlauf and drain the wort. I then add my first half of sparge water by having the water from my HLT flow in backwards through the manifold into the grain bed. This of course messes up the grain bed, but I have a pump, so once all of the water is added I just give it a good stir, turn on the pump and vorlauf until clear, and then divert to the boil kettle. I then repeat, again adding the sparge water through my manifold.
When I do have a mash that might stick, I simply add extra water at the end of the mash (~ 1 gal) to thin out the proteins and sticky dextrins so they can more easily pass through the grain bed. Then I do my first drain. I then use less sparge water to keep the final volume the same. The thinner wort flows better and is less likely to stick.
To sum it up, yes a proper grain bed is important for a good sparge, but the wort itself can equally contribute to a sticking problem, and the cure for that is simple dilution