I saw someone ask if you used a lid? I thought that was a no-no?
Almost ALL pro brewing systems are covered and they have a very small outlet vent. The wive's tale that homebrewing has that says that covering your kettle is a no-no, is incorrect. In addition, homebrewers are schooled to have vigorous boil activity. This is also incorrect.
While avoiding DMS in your beer is important, it turns out that its not that difficult to avoid. An important factor is to be sure that the SMM (that creates DMS) is fully converted. That conversion has been shown to be complete in a typical boil by a number of researchers (even with Pils malt). But the fear is that your boil needs to vent everything to the atmosphere to get all the DMS out. As the pro systems show, you don't need to vent everything out to reduce DMS to inperceptible levels.
The boil does not have to be volcanic either. A lightly rolling boil that you can see is circulating particles in the kettle, is sufficient. That heat input is sufficient to convert all SMM to DMS in a 60 minute boil. If you are worried about expelling everything, I suggest that increasing the boil vigor for the last 5 minutes of the boil is sufficient. Opening the kettle cover is OK too during that period.
An important thing that brewers need to become aware of is: Thiobarbituric Acid. This is an important oxidizing agent that destroys beer prematurely. Look it up!
The thing about thiobarbituric acid is that it is created by boiling your wort too hard and/or too long. The connection with covering your kettle is that by covering the kettle, you can actually reduce the heat input to your kettle while still achieving acceptable rolling action.
The boil duration is another factor that is debatable. A popular contention is that you should always boil a wort with a high Pils malt content for at least 90 minutes to expel DMS. There is evidence that you can get by with a boil duration of 60 minutes with a Pils grist and still have low DMS in the beer.
But there are cases where you might want to boil a long time. Those styles that benefit from oxidation notes or Maillard browning are candidates. But these factors are not desirable in pale beers, so avoid boiling them for more than an hour.
The final factor that homebrewers need to consider is the amount of water they boil off during the boil. Pro-systems typically lose about 6 to 10 percent of the original wort volume during an hour-long boil. An uncovered homebrew kettle can easily lose more than 15% in an hour. So typical homebrewers are boiling off more than twice the water that the pro's are...and we know that many pro beers have high quality. Covering the kettle and reducing both the heat input and evaporation loss is an appropriate goal for homebrewers.
There are homebrewers that have found that decreasing their evaporation loss to 6% may be too low. They did have DMS problems in that case, but I can report that I've reduced my loss to about 10% and I haven't noted DMS in my recent beers. The brewers from the Low Oxygen forum think that 8% might be as low as you'd want to go. By the way, I used to have the lid on my kettle partially open with a max crescent opening of about 6 inches. I've revised that to only about a 1 inch crescent opening to successfully reduce my evaporation and heating rates.
I'm hoping you will consider this information and start doing some research and experimentation on your own. There are significant advantages to covering your kettle and boiling at lower intensity and duration.
, be) in order to adjust your boil-off rate. Just lower or raise the heat. Experiment with heat input levels until you get the boil-off you want.
