Sparging (or lautering) is done at the end of the mash process, before the boil. The purpose is to extract the sugars created by the mashing process and dissolve them into hot water to form wort. We will then take the sugary wort, add some hops, boil it and ferment it to make our favorite beverage: Beer.
There are three techniques for sparging: the fly sparge, no sparge and batch sparge. Traditionally brewers use a fly sparge, where hot sparge water is continuously sprayed over the top of the mash tun to replace the hot wort as it is drained from the bottom of the mash tun. This gives a continuous flow, ideally with the flow in matching the flow out. Commercial brewers will monitor the specific gravity of the hot wort coming out of the mash tun and stop when it reaches approximately 1.010 to avoid off flavors and tannins associated with low wort concentration.
Duplicating a traditional fly sparge at home does create some challenges for the homebrewer. One must have not only a method for spreading water continuously over the grain bed, but also constantly monitor the flow of the water into the mash tun to make sure the grains do not run dry or overflow. Also fly sparging is a slow process – requiring as much as 60-90 minutes in some cases.
Batch Sparge and No Sparge
Two alternatives to fly sparging are the “no sparge” and “batch sparge” techniques. For these techniques a fixed amount of hot sparge water is added to the mash tun, the tun is gently stirred to assure even extraction for the batch, and then the entire mash tun is drained into the boiler, often at a fast rate (i.e. just open the spigot). The “no sparge” option uses a higher water to grain ratio when mashing and drains it all out in a single operation, while batch spargers use two or more sparge water additions, draining the mash tun empty each time.
The downside of batch sparging is reduced brewhouse efficiency – since a significant amount of sugar will be left undissolved and be discarded with the grains rather than make its way into the wort. For example a homebrewer fly sparging might achieve 73% brewhouse efficiency while a batch sparger might only get 66% brewhouse efficiency. Homebrewers compensate by adding more grain and just take the hit on efficiency.
For a commercial brewer the extra loss would be costly, but for the homebrewer making a 5 gallon batch of beer adding 1-2 pounds of extra grain (perhaps $2-4 in cost) is not significant. For most homebrewers, the extra few dollars of grain is a good trade off when compared to the extra time and equipment needed to do a proper fly sparge. Batch sparging also has the advantage of higher gravity for the runnings, which will rarely come even remotely close to the 1.010 limit mentioned earlier.
An additional concern with batch sparging is that stirring the mash upsets the grain bed, allowing more tannins and grain bits to make it into the wort. To reduce this risk, some brewers use a hybrid batch sparge method where they add sparge water slowly to the top and avoid stirring or completely draining the mash tun. This hybrid method does require additional time for the water to flow through the grain bed – much like a traditional fly sparge.
Batch sparging is more popular than no-sparge because it lets you use a traditional water to grain ratio when mashing, a smaller mash tun (typically a 5 gallon mash tun for a 5 gallon batch), and achieves much higher efficiency than no sparge options.
Batch Sparge Calculations
The most popular is a two stage batch sparge with equal size batches (equal amount of wort drawn off, not equal amount of sparge water added). Two equal size runnings of wort (equal batches) also maximizes the extraction efficiency. Calculating the amount of water to add for each sparge is straightforward where boil_size_l is your target boil size in liters, mash_water_l is the number of liters of mash water added and grain_wt_kg is the grain weight:
Two stage batch sparge additions:
- batch_1_sparge_liters = (boil_size_l/2 – mash_water_l + grain_wt_kg * 0.625)
- batch_2_liters = boil_size_l / 2
If you have deadspace under the mash tun, you must also add that amount of extra water to the first batch. If you have the newest release of BeerSmith, you can get an optimal “equal runnings” batch sparge that duplicates the sparge water calculations described above by selecting any of the default batch sparge mash profiles. The batch sparge amounts needed are displayed using the brewsheet (Preview Brewsheet) for your recipe.
The next item to consider is how much extra grain is required to use your batch sparge method. Unfortunately it is difficult to know this in advance, since your mash efficiency will depend on the milling of your grain, efficiency of your lautering system and other factors. A good rule of thumb is to add about 10% to your grain bill (or alternately take about 7% off your starting overall brewhouse efficiency of the recipe) for the first try. Some people use this “rule of thumb” method to size their batch sparge grain bill.
If you use brewing software or a spreadsheet, you can calculate your overall brewhouse efficiency and use that number to properly size future batches. In BeerSmith, these calculations can be accessed from the “Brewhouse efficiency” button in the top section of any open recipe. This display your estimated overall efficiency and OG in the “Brewhouse Efficiency based on Target Volume” section. Enter your actual volume into the fermenter and measured OG into the dialog and the program will calculate your actual overall brewhouse efficiency which you can use for your next batch. After a few batch sparge trials you should have a good handle on what your brewhouse efficiency, and you can then use the “scale recipe” command to adjust web recipes to your personal brewhouse efficiency.