What is Brew in A Bag?
Brew in a Bag - or you will see it often abbreviated BIAB - is a style of mashing used in homebrewing of beer. The grains that make up the mash bill are placed into a large bag made of porous material that is placed inside the mash kettle (which also doubles as a boil kettle.) When the mash infusion is complete the bag is lifted out of the kettle and left to drain by gravity. Common draining scenarios include suspendeding the grain bag above the kettle and letting it drain back into the kettle or placing the bag in a container to drain and adding the wort back to the kettle. After the drain step, some brewers choose to squeeze the bag to get more wort out. Once the wort is in the kettle brewing continues in the usual way.
The Brew in a Bag style of mashing differs from traditional mashing in that there is no separate container necessary for mashing/sparging and boiling. In addition there are no separate mash and sparge steps employed.
Why Brew in a Bag?
- Less Equipment/Cost - Traditional mashing methods usually require home brewers to build a pourpose-built mash tun to do the mash and the sparge including a false bottom or screen and bulkhead assembly to drain. Brew in a bag eleminate the cost and trouble involved in buying or making this specialized piece of brewing equipment.
- Shorter Brew Day - By eleminating the need to employ a pour-over after the initial mash infusion is complete, then drain, then sparge Brew in a Bag brewers cut a good amount of time out of the brew day.
- Less to Clean - By eleminating the mash tun the brewer does not have to worry about emptying the grain out of the mash tun, spraying it out and scrubbing it clean. With Brew in a Bag you just dump your grain bag and rinse it out and you are done.
- Requires Less Space - For a brewer short on space, eleminating the equipment needed to do a mash means there is really just the need to store the one mash/brew kettle.
How can BIAB Calculator help me?
Brewing a beer that turns out like your recipe intended involves creating the right amount of wort to put into the fermenter at the right gravity (potential alcohol.) BIAB Calculator allows you to input your exact brewing system parameters so at the end of the brew day you end up with exactly what you want. There are several other mash calculators you could use, but BIAB Calculator focuses on the factors unique to Brew in a Bag to ensure the best possible results.
To ensure results it is highly recommended that you do some tests to get real values for some of the System values in your brewing setup:
- Kettle Size: Take a container of a known volume and fill your kettle to ensure you know your brew kettle's true volume.
- Trub: The next time you brew take a measurement of what was left in your kettle after you transfered as much as you can to the fermenter. Is there room beneatha pickup tube? Do you leave some material behind if you siphon? Knowing this value will ensure there is adequate volume into the fermenter. After all, that's the whole point of this.
- Boiloff Rate: Take your kettle and heat source and boil some water for a hour - measuring how much you started with and how much was left after one hour. Assuming you keep the rate of your heat source as close as possible from brew to brew you should be able to know the volume/hour Boiloff Rate for your particluar brewing system.
- Grain Absorption: Measure the wort in your kettle before you add the grain. Add grains, mash, and let the grain bag drain off as much as it can by gravity. If you normally squeeze the bag, go ahead and do that. Measure the wort again and the difference your grain absorption value (i.e., the water trapped in the grain that is never going to be beer.)