How important is the boil?

[Nick Good]

Hi guys,

I have been getting some really good results with my biab setup.

But while I was gazing into the boiling slosh the other day waiting to add the next lot of hops I noticed that there was more of that white foam from the hops if I kept the boil a little more aggressive.

How important is the boil? Is a simmer OK or do you need a grunty tumbling boil, if so the pot has to be watched in case it froths over. I mean for the whole boil.

I have some brews that are sometimes a bit watery and was wondering if this was the reason.

[Mark Thomas]

I've only been brewing for a year, but as far as I understand, you need at least a solid simmer for the full duration, to drive out the DMS off flavours.  Boiling harder is fine but that will concentrate the wort (i.e. result in higher gravity) so you'll need to add more water.  I like to err on the side of a stronger boil and higher gravity, and then just top up with a bit of filtered water at the end to bring the gravity down to target.  If you boil too softly and end up with gravity too low at the end of the boil, you can't do much about it.

[Scott H]

More that a simmer but less than a volcano. You want a rolling boil so when you look at it you can see the wort Turing over as such.