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Effect of boil intensity on final product?

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aubrey

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So I got my new brewpot so I can do full boils. I don't have a dedicated propane burner, so i was testing trying to get 6 gallons of water up to a boil on my grill and on my stove. The grill worked (took the grates off and sat the pot on the burner covers), but was very slow - would have taken over an hour to reach boiling, not to mention the rediculous amount of propane it would have taken. My pot is short and really wide so it covers two burners on my gas range, so that ended up being the better/faster way to boil it.

Problem is, with the lid on I can get a really nice rolling boil. Once I take the lid off, it drops down to a very gentle boil, barely more than a simmer. Aside from needing to adjust my pre-boil volume to account for less boil-off will a fairly gentle boil affect the end product any? Thermometer shows it hanging out at 210.5*F with the lid off, lots of small bubbles in the middle, and some larger ones at the edge. The water is cooling off now so I can see what my boiloff rate is.

I plan on getting the bayou classic burner in the next few weeks, but my AHBS Blue Moon clone kit will be here tomorrow, and i really wanted to break all my new equipment in.

TIA

-Aubrey
 
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aubrey

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Update: I just measured the post-boil volume and I started with 6 gallons and ended up with precisely 5 gallons post-boil so unless there is some reason that a less vigorous boil is undesirable, I think I'm going to go for it tomorrow with the Blue Moon clone full-boil on the stovetop.
 

Whisler85

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are you brewing all-grain?

because if you are, you may not be boiling off enough DMS- which can leave you with a canned vegetable smell and flavor in your beer

all, 'boiling' means noticeably- 'simmering' may not isomerize your hop alpha acids properly and you may end up with a different level of bitterness/flavor/aroma from the hops than was intended
 

Kaiser

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What you are looking for from a boil is movement of the wort and evaporation of unwanted aroma compounds (DMS, gives a cooked corn taste and flavor to the beer). The former is needed for the proteins to coagulate and distribute the hops more evenly. The latter requires you to boil-off at least 8-10% /hr. And it is important that the escaping steam is not trapped by a lid. The lighter your base malt the more important does this become.

This being said, there is also an upper limit. If you boil-off more than 15%/hr you are risking heat damage to the wort. The wort may literally scorch on the pot b/c the circulation in the kettle cannot move it away from the hop spots quickly enough.

Kai
 

alpo

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You really want a good rolling boil. Not a splashing violent boil, but it should be pretty substantial. Simmering is not enough.
 

jcadwell

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Sorry to get off topic, but i have somewhat of a noob question relating to this. If i am doing an extact kit and want to do a full boil should you start out with 6 gallons instead of 5?
 
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aubrey

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Bummer. Guess I'll just have to do a partial boil and dilute.
 
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aubrey

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Sorry to get off topic, but i have somewhat of a noob question relating to this. If i am doing an extact kit and want to do a full boil should you start out with 6 gallons instead of 5?
Yes, because you'll have some "boiloff" where some of the water/wort will evaporate during the hour-long boil. You should do a test run with just water to see how much you lose during the boil (it varies based on your heat source and kettle) and use that as a guage for your pre-boil volume. The goal is to end with ~5 gallons.
 

BubbaK

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I never really payed attention to the boil off... I start with a 5 gal jug of spring water... measure off 2 gal to do a partial boil. When it is completed cooking, I pour the rest of the 5 gal into the fermenter.. guess thats why my first bottling job didn't fill 2 cases of beer.. :eek:
 
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