Dear Mr. Wizard,
I’m a partial mash brewer and formerly brewed single, 5-gallon (19-L) batches using 2.5 gallons (9.5 L) of water in the brew pot. After the boil was complete, we would then top off to 5 gallons (19 L) in the fermenter. Recently, we have begun to brew double batches by boiling 5 gallons (19 L) of wort in a single brew pot and topping off to 10 gallons (38 L) in two separate fermenters. In the double batches, we simply doubled all of the ingredients formerly used in a single batch (malt extract, specialty grains, hops and yeast). Will this method result in the same hop bitterness as the single batches since the volume of boiling wort is also doubled or are additional adjustments to the hops necessary?
The Wiz Responds:
Brewing beer, whether at home or in a commercial brewery, often boils down to balancing the investment of time with money. Commercial brewers are certainly more concerned with financial matters than hobbyist brewers, but the fact remains that time is valuable. And your question addresses this issue head-on.
Brewing high gravity wort and diluting later in the process is how almost all beer is made for sale to the public. Most brewers who use this practice produce high gravity beer all the way through aging and dilute with water prior to filtration and packaging. This is the most efficient method of brewing when one considers the cost of fermentation and aging tank space as well as the labor cost added to the beer when transfers and tank cleaning are considered. The method you propose only takes advantage of labor savings in wort production and is a form of high gravity brewing (albeit an abbreviated version). I do something similar to your method on a regular basis in a brewpub setting to produce wort for reasons that extend beyond labor savings and have had great success with dilution of high gravity (usually 2–3 °Plato higher than the target gravity) wort prior to wort cooling.
The recipe for this method is not a simple proportional increase in ingredients. Yields of brewing ingredients, both malt and hops, decline as their concentrations increase. For example, brewing wort with an OG of 1.096 (24 ºPlato) versus one with an OG of 1.048 (12 ºPlato) will not give you the same efficiency in the brewhouse. This means that more malt is required to achieve the same final wort volume.
On the surface, this fact is inefficient but it does have its advantages. Time savings is one obvious benefit. You can produce high gravity wort and then dilute to a greater volume and by doing so produce more wort in less time from a brewhouse limited to a given volume (which is the norm). The other bonus is a reduction of last runnings collected from the mash bed. This fact is often overlooked as wanton disregard for efficiency but many brewers choose not to collect dilute wort flowing from the mash. Kirin Ichiban is one such beer and this beer is marketed as only being made from first wort (undiluted by sparge water) flowing from the mash bed.
Hop utilization in the kettle boil also suffers from this method as utilization declines with increasing wort gravity and with the concentration of hop bittering acids in the wort. This is a double whammy and will require you to increase the hop dose to compensate for the reduction in efficiency. Your experience is consistent with this standard tid-bit of brewing wisdom.
High gravity brewing, as you propose, certainly has its merits but, like many things in brewing, has no exact formulas. In order to fine-tune, this method requires tweaking on your part to assess the performance of your mash/lauter tun and further adjustments to account for the decrease in hop utilization.
Don’t be discouraged by your task. Remember that yield from malt and hops decrease as concentration increases and that small steps towards your ultimate goal help to gauge the effect of high gravity brewing on yield and nailing your target. Most big brewers don’t venture above 1.072 (18 ºPlato) because yield becomes too low and fermentation gets funky as esters and higher alcohols get too high, even after dilution.
One way to get good yields from this method is using liquid additives to boost both sugars and hop bitterness. The most “modern” (and least traditional) breweries add sugar to wort either pre or post boil to adjust wort gravity and then add hop acids post fermentation to hit their bittering specifications. In fact, some brewers add most of their hop acids post fermentation in order to reduce hop losses in the boil and during fermentation. I am not attracted to these methods because I fancy myself as a traditional brewer (whatever that means!) but offer these techniques as fodder for the hungry homebrewing appetite. If you want to go crazy and dabble with these practices you can add malt extract or simple sugars to your malt wort prior to boiling and then dribble in some hop acids after the boil to move your bitterness closer to its target.