[center]Using Maxi-BIAB to Brew a 'Single Batch' Mini-BIAB.
by Ralph deVoil (Ralph)[/center]
[center]What is MaxiBIAB?[/center]
MaxiBIAB is a Brew In A Bag, All- Grain (or “All Mash”) method which is useful for making a full- sized batch where the kettle volume is less than the usual 23 L brew length. It is also a relatively simple and effective means for a novice brewer to try All- Grain brewing at full- scale early, so without the annoyance of small batches or a half- empty fermenter. Ordinarily, the de- facto standard brew length is around 23 L, MiniBIAB is around 13 L, but brewers can use the MaxiBIAB method to make full- sized 23 L batches in the same cheap and commonly- available 19 L stockpot they use for MiniBIAB.
MaxiBIAB involves sparging and post- boil dilution, processes which sound complex, but are really quite simple while also lending some clever advantages to the novice and experienced brewer in extracting decent efficiency and eliminating most of the reliance on brewing software to calculate volumes, temperatures and concentrations, actually making brew day simpler and much less hassle.
MaxiBIAB is very similar to MiniBIAB, but with a couple of simple tweaks, those smaller batches are a thing of the past and all that a MiniBIAB brewer requires is a food- grade 10L bucket and a common domestic kettle (about 1.5- 2L is fine).
[center]Why MaxiBIAB?[/center]
Cost- For any brewer already making kits, extracts or kits & bits, even MiniBIAB, upgrading to MaxiBIAB is trivial (see equipment below).
Simplicity- As with most BIAB brewing, the actual operations are very simple- compared to traditional 3-V brewing the method and equipment are both trivial, but the equipment is also readily- available.
Easy- Most of the anxiety and fiddling around in hitting volume and Specific Gravity targets are a thing of the past.
Space- Just the stockpot and bucket, often one even fits inside the other.
Low- risk All- Grain- MaxiBIAB is one method to try All- Grain brewing at full- batch scale that doesn't have significant equipment outlays or doing multiple batches to fill the fermenter and just like MiniBIAB, even if the brewer tries MaxiBIAB and for what ever reason doesn't like it, there's no great loss or expensive and now- useless pile of equipment in the shed/ garage.

[center]MaxiBIAB Equipment[/center]
If brewing kits already:

• 19L Stockpot
  BIAB Bag/ Swiss Voile
  Thermometer
  10L Plastic bucket (a larger one would be fine too, but let us not mention nappy buckets...)
  Large Sieve (150mm- 200mm)

Usually already present in most home brewing or MiniBIAB households:

• Domestic kettle for boiling water
  Domestic stove- top
  2L Jug for strike and sparge water
  Microwave oven/ small pan on the stove (optional)
  Mash Paddle
  4L Bowl/ Pan for temporarily resting BIAB bag, a larger one is fine

And if brewing MiniBIAB already:

• A 10L Plastic bucket

That's it!
[center]Checklist[/center]
Ingredients

• Grain- For a 23L batch at 1.055 in the fermenter, about 4.5 kg of grain is needed, 5.5kg is do- able though, even bigger beers are certainly a possibility.
  Hops- allow for slightly poorer hops utilisation, usually no more than 20%.
  Yeast- Which ever strain you like, dried or liquid.

Equipment

[center]MaxiBIAB Method[/center]
At a couple of points, MaxiBIAB has a couple of processes happening at the same time, it isn't quite one step after another. So, with this guide, I'm breaking it down into distinct phases, there's a couple of overlapping points, they will seem obvious when you're actually doing it.
Mash
Fill the stockpot to about 2/3 full, so 14- 15L, also fill the kettle and put it on to boil as well.
Heat stockpot to a slightly higher strike temperature, mash temperature + 4 or 5°C is good, even more will give you some room to manoeuvre and allow for some cooling while you get the mash under way.
When strike temperature is reached, remove a 2L jug- full of strike water and set it aside.
Put in the bag, rain in the grain and stir thoroughly. Measure the mash temperature- if it is just right, use the reserved jug of strike water to fill the stockpot, if too low then use the kettle of boiling, or if high then use some cold, or any combination- we want that stockpot full to the brim at just the right mash temperature. * Insulate the kettle well. Stir it half way through, longer mashes of 90- 120 minutes are probably better but not strictly necessary. Before the mashing time is up, start heating your sparge water, so put the kettle on and when it has boiled put it in the bucket then put the kettle on again. When lifting the bag, you want to be able to dunk it straight into 3-4L of really hot water. That's the end of Mashing.

* Congratulations, this is the first AG hurdle in many eyes- mashing at the 'correct' liquor to grist ratio. If you've used an ordinary 23L AG grainbill of between 4.5 and 5.0kg, in a 19L stockpot you've just mashed with the “optimum” liquor to grist ratio of around 4:1. Too bad that previous BIAB trail- blazers have shown that L:G really isn't all that important!

Sparge
Mash time is up! Lift the bag, drain it and give it a gentle squeeze to get some of the wort out, then drop it into the bucket with the hot water. There's no need to squeeze the life out of your bag of hot, wet grain though, just a gentle squeeze will do- it will be dunk- sparged in a moment anyway. Open the bag up, stir the mash and add more hot water if it isn't full to the brim: Notice the 'full to the brim' theme with MaxiBIAB! With the right volume ratios which are determined by the mashing and sparging vessels, there's no more calculating and measuring of water volumes!
Put the stockpot/ kettle on the heat to start bringing it up to the boil. Getting a sample is a good idea as is measuring the volume: Stir the grain a couple of times over the next 15 minutes, put the kettle on to boil again too.
Lift the bag, give it another squeeze then put it aside in the salad bowl. Pour the sparge liquor into the boil, you can get a sample of it and measure the volume if you want too. (This pic is before emptying the bucket.): Then sparge the bag again, just like the first sparge.

[center]Boil[/center]
So, when you originally lifted the bag out, you'd have about 12L of fairly concentrated liquor (about 1.070), put it on to boil straight away. The first batch of sparge liquor will probably be ready to add before the boil has started- add it. After the second sparge there may be too much liquor for the pot, that's fine- just reserve what ever is left (large container full): Boil as per the MiniBIAB guide, adding hops according to the recipe's hops schedule. Towards the end of the boil (but not right at the end), or whenever you think it will accept it, add the extra sparge liquor. Heating the sparge in a microwave will help. If it is too much, just use the leftovers for yeast starters!
Just before the boil ends, grab a sample. If you add sugar to your particular style, do it before the boil is finished and then get the sample: After the boil time is up, just leave it to sit for 15- 20 minutes, then drop the stockpot into the laundry tub/ kitchen sink to chill. Change the water a couple of times over the next few hours, but use the hot water for something constructive like cleaning up the kitchen.

[center]Post- boil dilution[/center] Ok, so our stockpot has cooled to pitching. We need to know the Specific Gravity and Volume of the wort (estimate the volume if need be- the kettle is usually full almost to the brim at the boil end, but shrinkage due to cooling will mean that there's a lower volume at pitching). We want the cooled volume, but don't under any circumstances open the lid or touch the wort until you are ready to pitch, even then anything that contacts the wort must be scrupulously sanitised.
Work out the dilution, this formula is usually good enough:

• Post- boil Specific Gravity / Target Specific Gravity * Post- Boil Concentration = Diluted Volume

For this formula a Specific Gravity such as 1.055 is expressed as 55.

• Required Amount of Water = Diluted Volume – Actual Volume

As per the MiniBIAB guide, pour the wort into the fermenter through the sieve.
Add the required amount of water, pitch the yeast (you can do this before adding the water to help stir it through).

[center]Discussion[/center]
Roots
Not surprisingly, MaxiBIAB is a variation on MiniBIAB, the main difference is sparging and post- boil dilution, plus a couple of other less- obvious quirks.
Because MiniBIAB is limited in terms of volume (or 'brew length'), and most brewers would like to work with standard fermenter- full batches (i.e. 23L) if they possibly can but don't want to spend any more on equipment (e.g. a bigger stockpot), some impatient (and bone- idle) brewers have tested and tuned a simple means to satisfy both of those criteria without sacrificing quality or quantity.

MaxiBIAB brings together the simplicity of MiniBIAB, sparging and post- boil dilution, they all go surprisingly well together.

More discussion here.