Techniques and Procedures
Fly sparge brings about the separation of grain from wort by adding water to the top of the tun at the same rate which the wort exits. The greatest efficiency percentage can be achieved with this style of sparging. However, it takes the most time. An average fly sparge can take well over an hour depending on the equipment used. This is because the wort must be recirculated (Vorlaufed) back to the top of the tun until it runs clear (10-30 minutes). Then the actual sparge must proceed no faster than 1 quart per minute (30-45 minutes depending on pre-boil volume). That is if everything goes perfectly and rarely do brew days go perfectly. It is very easy to drain too fast killing the efficiency or too slow and taking more than an hour. I have found it difficult to maintain the preferred mash out temperature of 170 F during the Vorlauf since I do not have a directly heated tun. My sparge water has to be over 180 F to keep the tun in the 160 range, but that is my equipment – yours may work better.
The real key to fly sparging is in the filtering device. There are two types: manifold and false bottom. The manifold style is a tube system made of PVC or copper tubing with thin cuts made every ½” or so. However, this version requires a coarse grain crush to avoid a stuck sparge and may lower the extraction efficiency due to wort channeling at the manifolds.
The false bottom is preferred. It is a screen or metal plate with hundreds of holes or many slits cut in it and placed just above the inside bottom of the tun. This style of filter is very efficient because it draws the liquid from the entire bottom of the tun. It is also more forgiving with the grain crush size – a little coarse or a little fine is alright.
Batch sparging shares some similarities with fly sparging. It must be recirculated until clear (usually less than 2 quarts), there is a filter at the bottom of the tun (only: ½” round x 12” long, give or take), and hot water is added to reach the desired 170 F temperature. There are usually two water additions after the initial strike water. The strike addition gets the mash to the correct ratio of 1-2 quarts of water to 1 lb malt. The next addition is to bring the first sparge liquid to a level of ½ the boil volume. That addition is used to bring the mash to 170 F. The second infusion is added after the tun had been drained; again to reach 170 F and the second ½ of the boil volume. This whole process is well under an hour (after the mash saccrification is done).
When I started batch sparging, it was out of necessity. I was making a 10% beer and needed all the room I could get out of my mash tun. During the process, I discovered that my efficiency increased! I believe it is because I was able to maintain a temperature of 170 F before the run off. Also, it cut an hour out of my brew day. With batch sparging the tun is drained as fast as your equipment will allow.
Another benefit of batch over fly sparging is the Vorlauf. Because the false bottom has such a large surface area touching the grain, it takes much more time to “clear” all the little particles of grain. With the batch method, the screen/filter has a much smaller surface area against the grain. This means that there are significantly less grain particles that the filter needs to strain out. I hope that made sense. For more information on batch sparging, please visit Denny Conn’s site.