The most efficient and best way to brew a mashed beer is to collect and boil more than the full volume of wort you want to ferment into beer. Remember, you’re losing about 6 to 8 % per hour during the boil due to evaporation. Many of us homebrewers want to brew 23 L of beer but deal with a number of constraints that restrict our ability to boil 25 L of wort. If you use an electric stove top, for example, it’s inadvisable to boil more than about 15 L. Attempting to boil greater volumes could burn out the element. Also, attempting to move 25 L of hot wort is difficult and dangerous. Cooling 25 L of hot wort also takes time (you’ll definitely want a wort chiller). The solution is to boil a concentrated wort.
In a concentrated wort, instead of adding water to the brew pot, cold water is added to the fermenter. This is also called ‘high gravity wort boiling’ since the density of the wort is higher. The advantages? You deal with a smaller pot, less hot wort and bringing the wort down to pitching temperature is a breeze. There are some drawbacks, however. Here are some things to consider:
- It becomes very difficult to accurately read your original gravity. The wort and the water might look mixed, but you might find that one hydrometer reading differs from another due to the differing ratios of water to wort in the testing jar.
- You’ll need more malt: Lets assume you’re boiling half of what you’re recipe calls for (12.5 L instead of 25 L). Use 1.4 times more malt than the recipe calls for in order to hit your target original gravity (which has become almost impossible to accurately measure)
- You’ll need more hops: A concentrated wort means lower hop utilization. Those hop oils are having a more difficult time diffusing into the dense wort. Multiply the hop amounts by 1.1 to make up for this.
If you’re concerned with hitting your target O.G., knowing, with certainty, your A.B.V. and understanding the efficiency of your brewing system, a concentrated wort might not be for you. If you just want an easier way to make some great beer at home, this method works wonderfully.