So I've noticed there's a lot of questions here in the beginners sub involving BIAB (brew in a bag). I've only done a handful of batches that way myself but I figured I could answer as many of the basic questions as I can think of, some other people can add a few things and then we can always link back to this thread when people ask these same few questions again.
Why BIAB?
BIAB is essentially a cheaper (equipment wise) simple way to do all-grain brewing because it doesn't require a lot of extra equipment like a mash-tun. The only extra equipment you need from extract brewing is a bag. They are easy enough to find and cheap enough at your LHBS or online retailers. Just get something that says BIAB or brew in a bag on the packaging. I know some members outside North America have made their own when the pandemic made having things shipped difficult. Any food safe material that will allow water through while filtering most solid materials out will do. Mesh, muslin and cheesecloth are all fine but I don't like cheesecloth because it drains water through it too slowly for my taste. You want to make sure you have someway to secure it, such as a drawstring, so that it doesn't touch the bottom of your kettle where it could get scorched. As far as your kettle the general rule of thumb is you want to go twice as large as the desired end volume of your batches. For instance I target 5 gallons in my fermenter, I bought a 10 gallon kettle. Found I could do 4 gallons in my borrowed 7 gallon turkey fryer but it wouldn't hold the mash volume of a 5: gallon batch without overflowing.
Grains
You typically just get your grains through whatever supplier you source the rest of your ingredients. I typically use MoreBeer because I take advantage of their free shipping program and my LHBS tends to be pricier. Your grains will need to be milled but I choose to order them unmilled and do it myself. If you're going to have your LHBS mill it for you ask them to mill it real fine or tell them it's for BIAB. Without going into depth for the reasons why (someone else can do that better) BIAB benefits from a finer crush than you'd normally want for all-grain. Since this has come up in multiple threads lately: IT'S VERY DIFFICULT TO CRUSH TOO FINE FOR BIAB. You might have a fair bit of flour, that's ok. If you can't get it milled you can pulse it in a blender, food processor or coffee grinder, whatever works but if this is a hobby you're planning to stick with I recommend buying a mill. Corona style mills (just Google corona mill) are fairly cheap and they're also pretty easy to convert for use with a power drill. Not necessary to convert it but it'll make the task much quicker and easier. I always double mill my grains too so once you're done put it through for another pass.
Mash
BIAB is typically done as a full volume mash. What this means is that you aren't starting with a smaller volume and sparging until you reach your pre-boil volume. You're instead mashing with enough water that after your loses to grain absorption that you'll be at your pre-boil volume without having to really top up. There are any number of BIAB calculators that you can find online to figure out your water for your mash. There is no need to sparge or rinse the grain bag with hot water but it's ok to squeeze it while draining over the kettle. Squeeze that thing until you feel you can't squeeze anymore out or you hit pre-boil volume. Once your done with that take a hydrometer reading and then prep for your boil. One last thing to keep in mind is that you typically do not want to really fire your kettle when your bag is in because of risk of scorching it so it's good to have a nice thick blanket or sleeping bag to wrap your kettle in to insulate it during the mash. I typically check in every 15-20 minutes to check the temp and give it a quick stir and then cover it back up. If you do want to fire the kettle during the mash I'd advise extreme caution and a really low flame. Keep in mind that you can also always adjust the mash temp up or down by adding hotter or cooler water.
That's about all I got off the top of my head. It really is pretty simple and less scary than it seems. If anyone wants to add or amend any of that go ahead
Why BIAB?
BIAB is essentially a cheaper (equipment wise) simple way to do all-grain brewing because it doesn't require a lot of extra equipment like a mash-tun. The only extra equipment you need from extract brewing is a bag. They are easy enough to find and cheap enough at your LHBS or online retailers. Just get something that says BIAB or brew in a bag on the packaging. I know some members outside North America have made their own when the pandemic made having things shipped difficult. Any food safe material that will allow water through while filtering most solid materials out will do. Mesh, muslin and cheesecloth are all fine but I don't like cheesecloth because it drains water through it too slowly for my taste. You want to make sure you have someway to secure it, such as a drawstring, so that it doesn't touch the bottom of your kettle where it could get scorched. As far as your kettle the general rule of thumb is you want to go twice as large as the desired end volume of your batches. For instance I target 5 gallons in my fermenter, I bought a 10 gallon kettle. Found I could do 4 gallons in my borrowed 7 gallon turkey fryer but it wouldn't hold the mash volume of a 5: gallon batch without overflowing.
Grains
You typically just get your grains through whatever supplier you source the rest of your ingredients. I typically use MoreBeer because I take advantage of their free shipping program and my LHBS tends to be pricier. Your grains will need to be milled but I choose to order them unmilled and do it myself. If you're going to have your LHBS mill it for you ask them to mill it real fine or tell them it's for BIAB. Without going into depth for the reasons why (someone else can do that better) BIAB benefits from a finer crush than you'd normally want for all-grain. Since this has come up in multiple threads lately: IT'S VERY DIFFICULT TO CRUSH TOO FINE FOR BIAB. You might have a fair bit of flour, that's ok. If you can't get it milled you can pulse it in a blender, food processor or coffee grinder, whatever works but if this is a hobby you're planning to stick with I recommend buying a mill. Corona style mills (just Google corona mill) are fairly cheap and they're also pretty easy to convert for use with a power drill. Not necessary to convert it but it'll make the task much quicker and easier. I always double mill my grains too so once you're done put it through for another pass.
Mash
BIAB is typically done as a full volume mash. What this means is that you aren't starting with a smaller volume and sparging until you reach your pre-boil volume. You're instead mashing with enough water that after your loses to grain absorption that you'll be at your pre-boil volume without having to really top up. There are any number of BIAB calculators that you can find online to figure out your water for your mash. There is no need to sparge or rinse the grain bag with hot water but it's ok to squeeze it while draining over the kettle. Squeeze that thing until you feel you can't squeeze anymore out or you hit pre-boil volume. Once your done with that take a hydrometer reading and then prep for your boil. One last thing to keep in mind is that you typically do not want to really fire your kettle when your bag is in because of risk of scorching it so it's good to have a nice thick blanket or sleeping bag to wrap your kettle in to insulate it during the mash. I typically check in every 15-20 minutes to check the temp and give it a quick stir and then cover it back up. If you do want to fire the kettle during the mash I'd advise extreme caution and a really low flame. Keep in mind that you can also always adjust the mash temp up or down by adding hotter or cooler water.
That's about all I got off the top of my head. It really is pretty simple and less scary than it seems. If anyone wants to add or amend any of that go ahead
