After the mash is over, the wort is at its sugary and stickiest. This means it will stick to the leftover grain and therefore you’ll lose some precious beer in the long run. This is reclaimed by sparging (or lautering as it is sometimes called), which is essentially rinsing the grain bed using hot water to extract the wort. There are two common ways this is done – fly sparging and batch sparging. In this article we will talk about them both and the strengths and weaknesses respectively.
The fly sparge, also known as the continuous sparge, is generally considered to be the most efficient sparging method and is therefore used in the majority of commercial breweries; it is also the traditional method for homebrewing. Fly sparging works by continuously adding water to the top of the mash. This water then permeates down through the mash bed extracting the sugars as it goes. Clearly if this sparge water is constantly being added, the mash tun will overflow if given enough time, therefore the wort is drawn slowly from the grain bed. It is important that the extraction rate matches the rate that the sparge water is added. To complicate things, the level of sparge water should be kept only slightly above the grain bed whilst the grain bed should also not run dry; quite the balancing act. The efficacy of this extraction can be altered in a number of ways, such as altering the particle size of the crushed grain, grain depth, speed of draining, temperature of the process, pH, etc.
It is also important to ensure that the grain bed is not disturbed as a result of the incoming sparge water, most homebrewers use a sprinkler head to gently replace the wort with sparge water, this is often gravity fed from a hot liquor tank.
In a well-designed fly sparge system, homebrewers can attain very good extract efficacies; this is the main advantage and is what attracts people to it, whilst also requiring less water when compared to batch sparging. The amount of sparge water required depends on the amount of water used in the mash. If the beer you’re making has a large grain bill, it will require more sparge water regardless of which method is being used.
In summary, when this method is executed well it is better than the alternative in terms of efficiency.
Despite being more efficient, there are disadvantages to fly sparging. When we spoke about fly sparging earlier, we were talking about a good, well assembled system. This is not something which is easily achieved and often requires a trial and error process to get a well-functioning system. Even once you have a good system set up, it needs to be monitored to ensure that the grain bed remains covered and the flow rate is appropriate.
In addition, the sparge water needs to flow gently and evenly through the grain bed, another aspect which needs to be monitored. If the wort is flowing too fast, it is said to channel. Channelling means that the areas of the grain bed which have water flowing through them will have their sugars extracted. The other areas will be left almost untouched, therefore lowering the extract efficiency. False bottoms are designed to prevent this channelling, but this requires further investment in your brewing equipment.
As the end of the sparge approaches, the pH of the water increases and needs to be monitored. Should the pH rise above 6, tannins will be released from the grain husks, causing an undesirable astringency.
Batch sparging is a much simpler, more straightforward approach to extracting the sugars held in the left-over grain, but it does require some simple maths. In order to conduct a batch sparge, you must know your pre-boil volume and how much grain you have used. First, all of the wort is drained from the mash tun, the first portion of wort will be particularly cloudy, this is often collected and re-added to the mash tun, this is known as a vorlauf. Afterwards, the mash tun is filled with sparge water, the volume of which depends on your pre-boil volume. The grain bed is then disrupted, commonly through stirring and the sparge water is then fully drained from the container, extracting sugars as it does so.
This method is not popular in commercial breweries as it has a lower extract yield compared to a well conducted fly sparge. However, for a homebrewer this method is simple, and while the yield may be slightly lesser compared to fly sparging, it can be easily countered by adding a small amount of extra grain. In a large scale, commercial brewery, the extra grain which would be required to counter the lower efficiency would cost a huge amount. However, in a standard 5-gallon batch brewed by a lowly homebrewer, the cost is negligible.
If the difference between extract potentials is the only worry, then the question is, by how much does it differ? Studies have found that at most, a difference of .004 gravity points was observed, with many other studies finding no difference at all. While these experiments are not definitive, it does show that the extra efficiency obtained by fly sparging is limited at best.
An honourable mention to the third sparging method: no-sparge. This is exactly what it sounds like, sparging is skipped altogether. A very thin mash is required, usually with around 3.5 litres of water per 0.5 kg. The wort is just drained from the grain bed, as you can expect, the no-sparge method has a lower extract efficiency compared to fly sparging and batch sparging. Nevertheless, the technique is straightforward and requires no additional equipment.
To summarise, if you have the time and the equipment, fly sparging is the way to go. You get high efficiency from your brewing, but the time it adds onto your brew day and then you have to think about the time it takes to actually assemble a good system. If you’re put off by all that, batch sparging is the choice for you, simple yet much more effective than the third option of no sparge. Batch sparging adds virtually no time onto your brew day, requires no extra equipment whilst increasing the quality of your beer. The choice is yours.