What are the disadvantages of a weak boil?

Lets say the heater doesn't provide much BTUs, but is able to take a 6 gallon wort to break a boil, but when leaving the lid off will slow down to a weak boil.

Besides longer boiling times or adjusted pre-boil volumes (I adjusted my beersmith equipment to boil-off 0.25gal per hour) what are other disadvantages?

Will it produce off-flavors? Assume the pot is kept uncovered (no DMS).

My next purchase is going to be a proper burner, but this is what I'm working with right now.

 

Just to be clear, you cannot boil with the lid on as the dms won't boil off.

 

Exactly. That's what I meant. I usually bring it to a boil with the lid on and as soon as the boiling point is reached I take the lid off and leave it off. I don't even leave it partially on as I don't want to take the chance of some DMS condensating on the underside of the partial cover and falling back into the wort.

 

Possible scorching of the wort at the bottom of the kettle is possible. Do you get a good hot break?

 

Boiling is boiling. The only difference between a vigourous boil and a timid boil is evaporation.

 

If it is actually boiling I don't think you risk much, if anything. as long as you have dialed in your boil off rate. Otherwise you will end up with too much wort and a lower than expected OG.

 

Boiling is not only boiling though. You can still have a simmer or a light boil. One the stove especially it is difficult. What you worry about is DMS particularly with Pils malt. The more vigourous the boil, the more stuff is kicked off. I am also guessing that hop isomerisation happens more with stronger boils but I am not sure about that.

 

Agreed. A weak boil will have a harder time driving off DMS. I have experienced this personally with a pilsner. Had trouble with my burner, and only managed a weak boil for most of the 90 minutes. Definitely had DMS flavors in the finished product.

Next time only did a 60 minute boil but it was very vigorous. No DMS flavor at all in the finished product. Not very scientific I know, but good enough for me. I now make sure all my boils are "vigorous".

I'm sure with most respects "boiling is boiling" (sanitation, isomerization, maillard reactions, etc), but with DMS, I'm convinced you need a strong boil, at least when dealing with Pilsner malt.

 

It all stems from how weak is weak. True if it is just barely boiling DMS is a concern (all grain, minimal with extract as most is already boiled off in creating the extract.). If it is a steady roiling it is probably OK. Large proportions of Pilsner malt will accentuate DMS problems though.