The Split Wort Increased Gravity (SWIG) Method
Imagine the slick salesman’s pitch. Would you like to reduce your brewing equipment costs? Would you like to brew two different all-grain batches of beer in the time it would usually take to brew one? Would you like to improve your love life? You can have all this and more, with the Split Wort of Increased Gravity (SWIG) method!
Like many long-time homebrewers, my brewing techniques and equipment have changed and evolved over the years. My first all-grain equipment was a bucket-within-a-bucket lauter tun (as popularized by Charlie Papazian in his “Joy of Homebrewing”) and two 20-quart stainless steel-pots picked up cheaply from a local hardware store. I would split a full-wort boil between the pots and usually had good results. Now — after building a propane-fired, three-tier, converted-keg system — I’ve actually moved back to the old two pots on the stove method, but with a few modifications. I sometimes still use the three-tier system when I want to make a lot of the same kind of beer, and when it’s warm outside. But I developed SWIG to diversify the kinds of beer I have on hand, and to brew through the cold winter months, of which there are many in Canada where I live.
SWIG should appeal to a couple of types of homebrewers: Small-scale (five-gallon) brewers who want to increase their volume without increasing brewing time or equipment costs; and larger-scale (10–12 gallon) brewers who find they end up with a little too much of one style of beer and would like some diversity in their brewing.
SWIG: The Theory
SWIG combines two common brewing techniques that have been practiced for decades: parti-gyle lautering and concentrated wort boiling.
Parti-gyle
Parti-gyle lautering is the practice of drawing off a portion of the mash liquid (the first runnings) for a strong beer, then adding more hot liquor and drawing off a second (and sometimes a third), weaker running for successively lower-gravity beers. Parti-gyle lautering has probably been practiced as long as grains have been mashed. In modern brewing, parti-gyle has a distinguished history in both English and Belgian traditions. In 18th century Britain, brewers used the same mash to make a strong beer (often denoted XXX), a common beer (XX) and a small beer (X). The technique was abandoned for the most part with the advent of porter brewing, which used “entire” mashing, meaning the beer was brewed using the entire extract from a mash. In Belgium, the parti-gyle technique gave rise to the three strengths of Trappist ale, the tripel, dubble and single.
Parti-gyle presents a few challenges to the homebrewer. The first is in recipe formulation. The gravity of parti-gyle worts are harder to predict than a standard mash, because the decrease in run-off gravity throughout the sparge is not linear. Also, the SWIG method is not as efficient as some homebrewers are used to. It is difficult to squeeze every last drop of sugar out of the mash, and total efficiencies are usually in the range of 65 to 75 percent. A lower efficiency presents a second challenge: getting enough grains in your mash tun to make up for the loss from efficiency.
Concentrated Wort Boiling
Concentrated wort boiling is a practice that has gained favor in modern brewing, as it permits a larger volume of beer to be produced in a brewery compared to full-wort boiling. Many breweries ferment a high-gravity wort, diluting the beer to normal gravity before packaging. On the homebrewing scene, most extract brewers are familiar with this technique — boiling their malt extract with a limited amount of water, then cooling and diluting the concentrated wort with water before pitching the yeast.
Concentrated wort boiling has its own pitfalls, the first and foremost being the quality of the water used to dilute the boiled wort. As one of the reasons for a full boil is sterilization, the water used in concentrated wort boiling must likewise be sterile. I’ve found that fresh reverse-osmosis water further treated with UV light for sterilization seems to work well. I try to buy dilution water the day before brew day, to ensure the water is as fresh and microbe-free as possible.
There are other challenges to concentrated wort boiling. For example, because the alpha acids in hops are less soluble at higher gravities, calculating hop bitterness is different in a concentrated wort as compared to a full-wort boil. Also, wort darkening during the boil is more pronounced because of the higher gravity.
SWIG: The Method
There are three key phases to the SWIG method: recipe formulation, planning, and brewing. As mentioned above, SWIG recipe formulation presents two challenges over standard approaches in that mash efficiency is a little more difficult to predict, and reduced hop bitterness extracted at higher wort gravities requires adjustment to the amount of hops added for bitterness and flavor.
Recipe Formulation: Predicting the Original Gravity
As with any mash method, the gravity of sweet wort collected depends on many factors, which vary from brewer to brewer. For SWIG, the challenge is to predict the gravity of two finished beers. As a starting point, I’d use Randy Mosher’s figures for parti-gyle brewing (Mosher, Randy: “Parti-Gyle Brewing,” Brewing Techniques, March-April 1994) and then fine-tune your numbers based on your system. Mosher suggests that in a parti-gyle mash split into two equal batches, the first runnings will take 58 percent of the expected extract, while the second batch will take 42 percent. This means that if a recipe should produce 10 gallons of 1.050 beer, the first five-gallon batch will be a 1.058 beer, and the second a 1.042 beer.
I’ve found that with the SWIG method, because mash efficiency is fairly low due to the limited sweet wort collected, the numbers work out to be closer to 60 percent/40 percent with my system, assuming a 65 percent mash efficiency. For example, a mash that would produce 10 gallons of 1.056 gravity wort at a brewhouse efficiency of 65 percent, will produce a 1.067 and a 1.045 wort using the SWIG method. This is for recipes with 20–24 lbs. of base malt. In theory, if you are mashing less malt, your efficiency should rise because you are using a smaller ratio of malt to sparge water. As a consequence, the differential between the two batches should also rise. Of course, mash (or “brewhouse”) efficiency will vary from setup to setup. Efficiency is dependent on a large number of variables, from grain crush to mash regime. However, 65 percent is a good estimate to use until you’ve done a few SWIG batches and figured out the actual efficiency of your own system.
The color from the mash seems to follow the same ratio as extract. In other words, if your 1.056 mash has a predicted MCU of 12, the first wort will have a MCU around 14.5, while the second around 9.5. I believe that it’s important to calculate the distribution of color as MCUs rather than SRM, because the former is linear. Once calculated, you can then convert the number to SRM to check style conformance.
One advantage of SWIG brewing is that you can add specialty malts to the second mash session, creating an entirely different second wort. This means you can brew a stronger, pale beer and a weaker dark beer, two pale beers of different gravities, or two dark beers of different gravities. By adding sugar or malt extract to the kettle, you can brew two beers of similar strength. See the table above for some ideas for successive beers using SWIG.
The second addition of specialty malts will add color, flavor, body and possibly a few points of extract. Very little specialty malt is required to add color and flavor — typically 0.5 to 1.5 pounds will suffice.
Recipe Formulation: Accounting for Hop Bitterness
There are several methods of calculating hop bitterness. At least two of them account for wort gravity — Garetz and Tinseth’s methods are detailed in Norm Pyle’s Hop FAQ (http://www.realbeer.com/hops/FAQ.htm). At higher gravities, alpha acids are less soluble, meaning less bitterness is extracted from the hops. Comparing Tinseth’s calculations for a normal 1.059 SG boil to a SWIG 1.059 batch (a 1.084 boil diluted to 1.059 with water) suggests that utilization is about 30 percent lower for the higher-gravity boil. This means that you need to add about 30 percent more bittering hops for recipes adapted to SWIG brewing.
Planning: What’s Different?
SWIG brewing requires a little more forethought, as managing two simultaneous boils is challenging. My planning is aimed at saving time and making the double boil as easy as possible. A few changes to standard brewing procedures can make a SWIG session easier. First, consider first-wort hopping (FWH) for bittering hops. First-wort hopping means that hops are added to the wort as it is collected, at near but not at boiling temperatures. First-wort hops are thought to contribute flavor and aroma characteristics as well as bittering. This makes the first hop addition easier, and usually means fewer flavor or aroma additions are required. Calculate total water use beforehand so that you have enough purified topping up water on hand.
Several steps in your brew day will be concurrent. For example, if there is a 30 minute lag between worts, the following will be true: While you are collecting the first wort, you are heating the sparge water for the second wort. While you are re-circulating the second mash, you add bittering hops to the first wort. While you are bringing the second wort to boil, you add flavor hops to the first wort. While you add flavor hops to the second wort, you are chilling the first wort. While you are transferring the first wort to the fermenter, you are chilling the second wort. It is useful to track the times on each pot to ensure you add hops and Irish moss at the right times for each brew.
Final Thoughts
I developed SWIG to be able to brew more kinds of beer with less effort. I’ve discovered it produces very good beer — as good as the beer I was making with full-wort boils. There are many advantages to SWIG, including decreased energy and chilling water usage, decreased equipment costs, the ability to brew indoors, avoiding over-sparging, and the ability to produce two different beers from the same mash in the time most brewers take to make one. There are many permutations brewers could make with this technique, limited only by imagination and the number of burners on your stove. For the brewer already doing full-wort boils on the stove, it would be a simple adjustment to collect a concentrated wort, then a regular wort — all you need is an additional 20-quart pot. SWIG can also be used to brew smaller batches of stronger beer (such as dopplebocks, barleywines and Imperial stouts). And for the beginning all-grainer who wants to limit complexity, a single pot and 15 lbs. of mash could be employed for a single concentrated wort session with good results.
