There’s a Parti in My Pots, And I Saved Money, Too

BYOB by | Oct 2008 | Issue #21
Illustration by Scott Murry

Homebrewers are cheap bastards, looking to squeeze a dollar out of a dime. Yes, I said it and if you look deep in your heart, you know it’s true. Sure, sure, you’re willing to dole out $30 for funky Brett and bacteria or $45 for that stupidly extravagant pile of hops needed for your Triple IPA. But if you weren’t getting 5 gallons out of the process, would you pry open the wallet?

The professionals are the same. They have a business to keep running after all. Ancient brewers figured out that more sugar, beer and profit could be wrung out of their dreadfully inefficient mash. Separating multiple spargings of the mash and blending the results can yield beers of distinct gravities and character. The British call this process “parti-gyle” brewing. A few commercial breweries, notably Fuller’s, still brew their lineups using parti-gyle.

Thanks to brewers’ experimentation, we know how sugar flows from a mash. The rule of thumb: In a sparge, the first 60 percent of mash gravity comes from the first 50 percent of its runnings, the final 40 percent in the second half. Putting this trivia scrap to use in your brewery involves a little math. I promise it won’t hurt like college algebra. For simplicity’s sake, we’ll assume you’re brewing two equal-sized batches.

When formulating a “parti,” you think in terms of total gravity needed from the mash. By adding the gravity points in each batch, we can calculate a target original gravity (OG). Our total grain bill then is equivalent to calculating a full batch at that OG. The formulas:

Total Volume = (Volume first beer) + (volume second beer)

OG total volume = [( (OG first beer) x (Volume first beer) ) + ( (OG second beer) x (Volume second beer) )] / Total Volume

Of course you can’t just arbitrarily plan to brew a beer at two random gravities and expect it to work out. But pick a desired OG for the first beer and you can calculate what to target for the total batch and what gravity the second batch will be.

OG total volume = [(OG first beer) x (volume first beer)] / (Total volume x 0.6)

OG second beer = [(OG total volume) x (total volume) x (0.4)] / (Volume second beer)

This month, we’ll do a traditional split batch, 5.5 gallons each, Barleywine and IPA. Brewers use parti-gyle for big beers because the concentrated first beer requires a shorter boil. I want a booming Barleywine at 1.096, so plugging in the numbers:

OG second beer = (80 x 11 x 0.4) / (5.5) = (352) / (5.5) = 64 = 1.064

OG total volume = (96 x 5.5) / (11 x 0.6) = (528) / (6.6) = 80 = 1.080

According to the math, for a first beer at 1.096 we need to calculate a grain bill that would produce 11 gallons at 1.080. Our second beer should then be around 1.064. Nice and chunky! For parti-gyles, I give myself extra wriggle room and calculate at a lower than normal efficiency.

Sparge slow and keep an eye on your running gravity and pH. A pH above 6 will cause tannin extraction. The first 6.5 gallons of runnings go into my boil kettle. The other half lands in buckets or a second pot ready to be boiled.  If you have two burners, the timing works to allow you just enough time to boil and chill your first beer before the second beer finishes boiling.

Remain flexible! Sometimes the sparge doesn’t quite work out the way you think it should. Be prepared to adjust hopping or have sugar/extract on hand to fill a shortfall.

Although we’re not doing it in this month’s recipe, you can boost the color and character of your second beer by “capping the mash,” adding a small amount of fresh specialty malt to the mash before the second sparge. Capping gives you the freedom to make a Tripel and a Belgian Dark from the same base grain bill.

Try these pairs: Weizenbock / Weizen; Old Ale / Mild; Wee Heavy / Scottish Export; Belgian Golden / Belgian Pale Ale; Imperial Pilsner / Bohemian Pilsner.

Finally, search online for “Brewing Techniques Parti-Gyle” to find Randy Mosher’s article that taught many homebrewers how to parti. Mosher includes calculations for beers split in uneven volumes.


(Barleywine) 5.5 gallons at 1.096, 80 IBUs, 8 SRM, 60 minute boil / (IPA) 5.5 gallons at 1.064, 63 IBUs, 5 SRM, 60 minute boil

Efficiency: 69 percent

Malt / Grain (both beers)
17.00 lb. domestic two-row pale malt
17.00 lb. Marris Otter pale malt
1.00 lb. British Crystal 75L
0.50 lb. Biscuit malt
0.50 lb. Melanoidin malt
0.25 lb. Special B malt

Extract Version
Sorry, guys. No recipe for you!

Saccharification rest at 152°F for 60 minutes (strike with 9 gallons).

Barleywine Hops
1.00 oz Warrior (pellets) | 17.1% AA | 60 minutes
0.25 oz Chinook (pellets) | 13.0% AA | 60 minutes
0.75 oz Palisade (pellets) | 9.4% AA | 10 minutes
1.00 oz Cascade (pellets) | 5.5% AA | 0 minutes
1.00 oz Cascade (whole dry hop; optional but delicious)

IPA Hops
1.00 oz Magnum (pellets) | 12.9% AA | 60 minutes
1.25 oz Amarillo (pellets) | 8.8% AA | 10 minutes
1.00 oz Cascade (pellets) | 5.5% AA | 0 minutes
1.00 oz Cascade (whole dry hop; see note above)

Wyeast 1272 or WLP001 / Wyeast 1056 / US-05

Ferment IPA for a week in primary and age on dry hops for 2–4 weeks before packaging. The Barleywine will dictate its own pace!

1.080 = 80 * 11 * .6 / 5.5 = 1.096
1.080 = 80 * 11 * .4 / 5.5 = 1.064

Written under the influence of Stone’s 12th Anniversary Bitter Chocolate Oatmeal Stout and 21st Amendment IPA (in a can).