Brew-in-a-bag (BIAB) or “Posebryg” (in danish) is an Australian simplification of home brewing process that allows both brew-time and equipment costs to be lower. It is therefore a well chosen alternative for beginners where the more “normal” home brewing process is a little more time consuming. The version described in this website is even more simplified as we are looking at 5 – 10 Liter All-grain brewing, hence, we can make use of kitchen utensils in a larger scale. So, we shall both bake our beer in the oven, pour it into the sink and cool it in the fridge! Even BIAB can be used also for larger brews than 10L it just get a bit heavy to deal with in and around oven, lifting malt-ball and placing in sink, etc..

The Process of Brewing BeerBut first let’s take a look at the traditional process in contrast to bag brewing.
In the figure (of LGuerra) to the right the commercially brewing process is pictured and as such it is very close to process done by homebrewers, however, normally homebrewers do not do “malting” step. In the bag brew process we use a bag to both do mashing and filtering (lautering) in one step. In traditional home-brewing process one would recirculate  water after end mashing  using the mash-grain-bed as a filter until the liquid (wort) clarifies over a time span of  ½-1½ hours. This is done both to draw as many fermentable and less fermentable sugars out, but also to clear wort as much as possible (this gives easier a more clear beer in the end).

Bag brewers, as said above, do the mash and the filter  steps  (step 3 and 4 in the figure) as one step. The advantage is a simplification of the process, less equipment and especially shorter time. The downside is fewer sugars is extracted out in the mash step (= lower mash efficacy of 10 -20% less), and the wort is said to be less clear. Therefore the bag brewer often up-adjust malt quantity, and at use a more widespread use of fining agents such as Irsh Morsh. In addition, the bag brewer usually also use of a greater ratio of water during its mashing than the traditional home brewers.

If you would like to read a little more about the traditional home-brewing technique, please see “” Here there is also the explanation of many words / terms about brewing beer that I have not the right to explain to the fullest.

Temperature control, brewing and cooking utensils.

Beer brewing is very much a questions of temperature control. This applies to both mashing normally done in the range of 60-70 degrees (usually around 63-67 degrees), boiling (we all knows we boils at 100 degrees), rapidly cooling before yeast addition, and especially during fermentation.

As the mashing step involves enzymes that breaks starch into sugars and these have different temperature optimums, it is important to understand the impact of temperatures. In short, one can say:

Mashing temperature 63-64 ° C or lower provides a dry BEER

Mashing temperature 65-66 ° C or higher gives a slightly sweeter and richer (fuller) BEER

As a beginner you will go for about 65 degrees and not think to much about this. Bake your beer in the oven, is actually not so crazy an idea. Set the oven on just around 65 degrees and the furnace becomes a super incubator to maintain a constant temperature and thus help the important mashing of the malt. Both my 10 and 25 liter pot goes into the oven. The boiling we do is partly to sterilize the wort, but also to releasing bitter-hop flavor and/or aroma flavors into the beer. The boiling also removes/breaks down various undesirable substances. Cooling after cooking is especially important because the faster the fermentor is closed with yeast, the less risk of infection. You can do this in your sink with cold water, ice, dry ice etc. Or you can transfer the still hot wort to the fermentor and hence also sterilze the fermentor this way (this is called Eazy-Chill or hot-chill and normally done over he night).

Fermentation should usually for top-fermenting yeast be done around 18-20 degrees (wheat beer yeast perhaps a bit higher) and lager (bottom fermenting yeast) significantly lower around 10-12 ° C. It is not always easy to control this, but a cold cellar / utility room floor is a start. For larger beer (and as you advance in you brewing process) you will need a temperature controlled fridge. Cool your beer in the fridge after fermenting (cold crash) for 24-48 hours before bottling, is an advantage when fermentation is over (after 12-20 days). Hereby the yeast settle itself and the beer also clears further. So for a 5-10 Liter brew, it is possible to make use of kitchen utensils such as oven, sink and refrigerator for temperature control, which is difficult for larger brew.

Beginners and BIAB and batch sizes.

I started to brew in 5 and 10 Liter sizes (now late 2017 I went for 18-25L on my RIMS), mostly because I could handle it all on the kitchen table over a 3½ – 4½ hours. A 10L BIAB brew is nice if one can not devote eight hours a Sunday for brewing beer. The last is probably the biggest reason for the choice of bag brew method and a brew size of 10 liters! As a beginner, it is also appropriate with small brews, as there will be mistakes! The downside is that these bottles do not last very long time ….. you gotta taste how beer is evolving!