All Grain partial Boil (AGPB)The Idea:To brew a quality all-grain beer with minimum equipment, on the kitchen stove, and in just one kettle. Basically, it uses a stiff mash and small sparge to develop a high gravity wort. We're making our own extract. For beginners, this technique can be a great transition from extract/partial mash to all-grain while spending less than $30 on extra equipment. For more experienced brewers, it is useful to brew inside out of the cold, or to do a quick brew without breaking out all your AG stuff. I started experimenting with AGPB to keep brewing while my Kooker was broken.
The Caveats:[*] This technique only works for 5 gallon batches.[*] It only works for 'average' gravity beers. It's difficult to get above about 1.055SG and still use an average brewing pot.[*] More grain is required compared to full volume AG. Assume about 60-65% efficiency.[*] The beer will be a little darker than AG, the same as extract brewing.[*] Hop utilization will be lower, same as extract.[*] Batch sparging is the only way I've tried this.[*] Single infusion mash only.[*] Finally, have some DME on hand the first few tries.[/list]The Equipment:[*] Basic extract brewing equipment[*] 20 qt or larger kettle (same one used for extract)[*] Immersion chiller $20 (not absolutely required, but strongly recommended)[*] A cooler mashtun $12-$20[*] A mashtun manifold $6-$10 (check Denny for build instructions)[/list]The Recipe:At the most basic level, all that is necessary to convert a regular AG recipe to a AGPB recipe is to adjust for the lower efficiency and hop utilization. I use Promash to do these calculations so I'll explain with that as a reference. I'm sure other programs will work as well; I just don't know how to use them.Most published AG recipes are written for 75 or 80 percent efficiency. We are just not going to get that with the abbreviated sparge required for AGPB. If you're already doing AG, knock off ten percent. If you're just starting AG, use 60% as a starting point. Starting with a Promash recipe, click the 'Efficiency Lock' check box and click the efficiency down to around 60%. The grainbill will increase to compensate. Generally, you'll end up with 10-12 pounds of grain.Hop utilization is a little harder. Without promash, increase an AG recipe's hops by 20%. Using promash we can be more precise. First, we must change a system setting. From the main page, click Options > System Settings > Measurement, Sizes, Precision > then Uncheck Wort Size Always Equals Batch Size. Now back to the recipe, set the batch size to 5.0 gallons (locking to size if necessary) Take note of the hop IBU's for each addition. Next lower the wort size down to 3.0 gallons while watching hop IBU's decrease to account for the higher gravity. Manually tweak the hops amounts up to equal the original values.The Procedure:For brevity, I won't go into how to mash; there are plenty of sources available for that. I also won't explain the basic concepts of batch sparging. Denny's page has everything you need to know. The difference in AGPB is in the amounts of water used to mash and sparge. We're limited by the boil pot to a max of about four gallons of runnings. That means we should drain off two gallons of first runnings and two gallons of batch sparge. Keep the mash ratio low - definitely below 1.33:1. Promash will give exact volumes on the Water Needed page. For an average 10-12 lb bill, striking with around 3.5 gallons will give you 2 gallons of first runnings. Add two more gallons for your batch sparge, stir, recirc, and drain again.After draining the batch sparge, you should have 4 gallons of wort in your pot. Test the gravity now and multiply by 0.8 to get your approximate OG after dilution. If you're a little low, add some DME - 1/2 lbs of DME will raise the final OG by 4 points.After this point, you're just doing a regular extract boil, with a few exceptions. If you've never done AG before, you may be surprised by the amount of break. AG generally produces more break. Watch that pot closely! We're really pushing the pot volume here and boil-over is a big possibility, especially if you're used to all the room in a sanke kettle. [Edit*] Finally, I recommend one more change in procedure after the boil is over. Since the wort is so rich in sugar, we need to get everything we can from the pot. To help with this, I always drain off the wort, leaving behind as much break material as possible. I add my make-up water to the kettle, whirlpool and wait again, then siphon this diluted wort into the fermenter. Aerate, pitch yeast and wait.Good Luck! Edit: *Here's a refinement to the double whirlpool method above. Add hot make-up water to the kettle before you chill it. This works best if you have a big pot. For example, my 22 qt pot will hold 5.5 gal, but won't safely boil more than 4. So once the boil was completed, I added about 2 gallons of almost-boiling water (heated with the heat stick) directly to the pot. Then I cooled it all with the IM chiller. This way I leave 'weaker' wort behind with the break, but save the extra half-hour. Most importantly, I also overcome most of the sanitation concerns with make-up water.
