Bag End

This is the third post about the Brew-in-a-BAG (BIAG) mashing technique.  For the brewer of small and medium size batches it offers the chance to simplify the brew day, and that is always a good thing.  In this post I will give a few more pointers regarding what I think I know about the process, as well mention a few reasons why it might not be the best way to brew.  Also, the Basic Brewing Radio podcast has also discussed this techniques in some detail; don’t forget to check it out, too.

In the last post we discussed a theoretical batch 14 liters in size with a target of of 12ºP, and calculated it would require 2.84 kg of grain. At this point you have a choice on what to do.  A number of brewers simply add all of the batch’s required water to the mash, resulting in a very dilute mash, at least by the traditionalists.  I typically mash using 3 kg of water per kg of grain, which is close to 1.5 quarts per pound, which is on the high side of many brewers norm .  I honestly don’t know how thin a mash can be and still convert.  Despite what some may claim, I have never seen any definitive evidence that a higher or lower water to grain ratio has any impact on the beer flavor or quality.  That being said, I still superstitiously mash in at my regular 3 to 1 ratio, then add water to the pot prior to removing the bag.  Feel free to experiment here as you see fit, I doubt you can screw it up!

So, you add the water and the heat and the mash happens as the mash happens. Now it is time to drain the bag.  A couple of things about my process.  Since I use a 5 gallon / 20 liter pot I am usually starting my boil with 19 liters of wort.  This means that I can never actually add all of the water prior to removing the bag.  But it is important, in order to maximize extract yield, to add as much water as you can prior to removing the bag of grains from the boil kettle.  Think about it this way.  You have a sugar solution in the pot.  A given amount is going to be held up / absorbed by the grains in the bag.  The higher the gravity of the wort, the more sugar is in the solution, hence more sugar is held up in the grains.  The more you can dilute the sugar solution, the less sugar will be left in the grains.  So add all of the water you can before removing the grain bag.  I hope that is intuitive enough; if you are not convinced then run the numbers yourself and I think you will convince yourself.

Now once I remove the grain bag the liquid level in the pot drops. So after the grains have completed draining I add more water to top up my boil pot.  If you have the capacity to hold ll of the water and grain in your brew pot – go for it. Your efficiency will be all the better.  I guess I could soak the groan bag in this “top up” water and remove a bit more extract, but the gain is small for the effort required.  Remember, don’t worry, relax.

So, the BIAB method has lots of advantages:  less equipment to clean and because the grain the chances of a stuck mash are greatly reduced. In fact, I guess one could mill the grain finer than what is normally recommended.  I have not changed this part of my process.  I always double crush the grain, just to ease the strain on my mill.  For BIAB you really do not need to worry about how finely you crush the grain or how many grain hulls are intact – it won’t stick. Maybe someday I will measure the efficiency of grains milled under various conditions.

So BIAB offers lots of advantages.  Why wouldn’t a brewer use it?  There are situations where it will not work.  In my case, I am limited to worts of about 20 ºP original gravity.  Why?  As the mount of extract required goes up, more grain is needed.  This of course means that more liquid is held up in the grain bag.  Which means you need more grain.  Which means even more liquid is held up. You reach a point of diminishing returns, so to speak.  There is just not enough pot to hold the necessary grain and water.  This can be alleviated by making a smaller batch of beer, but overall for the higher gravity beers the efficiency drops precipitously.  So for those beers a conventional mash tun works best.

The other problem I have with BIAB is large batch sizes.  I have not found a good source for large (10 gallon) grain bags.  My wife did make me a grain bag for my ten gallon boil pot, and I have used it.  But here is the other side to that coin: when you have enough grain for a larger batch it gets heavy!  Lifting a rather warm and wet large sack of grain is not great fun.  And you really need to hang it up and let it drain for awhile (a step ladder makes a good rack to hold the bag), but whatever you use needs to be sturdy.  Lastly you have to be careful with your bag.  Using a jet burner I managed to melt a hole right through a grain bag.  That was not my most fun brew day.

So I will be BIABing for a few batches.  I will let you know how it goes.

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