Originally Posted by malkore
But remember that heat is what causes wort to produce DMS. Taht's why rapidly cooling the wort below 150F is so important. 150-212F is where DMS production happens.
So when you boil the extract, it could produce DMS again, especially if the extract is based heavily on Pilsner malt.
I agree with this guy. Lid off even with extract.
With a full boil you will need to start with MORE THAN 5 gallons so that after the loss to evaporation while boiling you end up with the proper volume of wort. I aim to have more then 5 gallons at the end of the boil because some beer is lost when racking to the keg.
I always start with 6 gallons of water + extracts. This boils down to 5+ gallons. I always have just the right amount to fill a 5 gallon keg.