Boil covered or not?

[Scuba_Steve81]

Sorry for the newbie questions...

Up until now, I have always boiled indoors and uncovered. Mainly, because my old extract setup didn't have a lid, so I had no choice...

I had assumed that covering was ideal though to hold in the heat and stop rapid evap.

My most recent brew was the first in a new, much larger kettle. This one came with a lid. I am still losing about 1.5g/h with the cover on, and the propane turned down to just enough to keep me boiling.

In recent reading though, I think it is suggested to boil with the top off.

Is this correct, and if so, why?

I'm also worried about 2 hours including cool down time with the top off, allowing the outdoors to make its way into the wort!

 

[Foosier]

Uncovered. Always.

Keeping the boil covered does not allow certain volatile chemical precursors like DMS (Dimtheyl Sulfide sp?) to dissipate. DMS can lead to a pronounced "creamed corn" flavor in your beers. This is mostly an issue when using Pilsner malts.

 

[kh54s10]

There is something called DMS. Di-methyl Sulfide, I think. It will give you bad flavors. If you boil with the lid off it will be driven off in the steam, lid on it condenses with the steam and drips back into the wort.

For cool down use an ice bath, immersion chiller, counterflow chiller, plate chiller or just cover and pitch the yeast when at the yeast's ideal temperature.

 

[m1k3]

Uncovered. Always.

Keeping the boil covered does not allow certain volatile chemical precursors like DMS (Dimtheyl Sulfide sp?) to dissipate.

Also, with all grain you are doing a full wort boil so an uncovered pot will give the needed boil off rate to increase your gravity.

It is ok to cover the pot post boil (during chilling) to keep stuff from falling into the cooled wort to prevent infection.

 

[atom]

yes...boil uncovered. evaporation is good (you have to account for it though). you probably don't have to worry about leaving it uncovered during chilling, you can cover at this point but it will increase your chilling time.

 

[mongoose33]

When you're bringing it to a boil, you can have the lid on--it'll help the boil kettle come up to temp much faster. But once you get close, remove it and leave it off, as per the reasons cited above.

I'm also worried about 2 hours including cool down time with the top off, allowing the outdoors to make its way into the wort!

Cover it for that--at this point, all the boiling and driving off of precursors is finished, and you *should* cover it unless you're you're looking for indigenous wild yeast to take up residency--and anything else that wants to fly in.

 

[BlurryEyed]

I'll cover until the boil is rolling. Once it's rolling - uncovered until I'm chilling.

But remember...an unwatched kettle will surely boil over.

 

[buzd]

I'm also worried about 2 hours including cool down time with the top off, allowing the outdoors to make its way into the wort!

My last batch has a few grass clippings in it. Doesn't seem to have affected anything.

 

[Scuba_Steve81]

Great advise. I hope my current brew doesn't taste like corn! It was 40% Pilsner.

My top was not tight fitting, and a ton of steam did pour out. Also I boiled for 90 min, and lifted the cover to stir about every 15.

Fingers crossed!

 

[mabrungard]

Since boil off rates typically experienced by homebrewers can be much higher than desirable and much higher than experienced in covered pro kettles, it is appropriate to partially cover your kettle during the boil. Pro systems often experience only 5 to 8 percent volume reduction in a one hour boil. Compare that to well over 10 percent in most uncovered homebrew kettles. When you plan for an appropriate boiling volume reduction, you can reduce the pre-boil volume and not have to waste the extra energy needed to get rid of that water.

As an example: Many brewers can evaporate about a gallon per hour from their 8 to 15 gal kettles. If you are starting off with 6 gallons and taking that to 5 gallons, that is a 16 percent reduction. If you have that same loss rate but only start with 4 gallons, that's a 25 percent reduction! This can become a significant problem since that volume reduction also concentrates your water's mineral concentrations. There have been plenty of brewers that have found they have to reduce their mineral additions to keep their beer from being too 'mineraly'.

Partial cover provides sufficient exchange with the atmosphere to vent DMS and to reduce evaporation. If its good enough for the pro's, its good enough for me.

 

[TexasWine]

Yup, what Martin said. My opinion, 1.5 gallons per hour boil off is more than what's required. I like to have mine around 0.6 to 0.7 gallons per hour for 7 to 14 gallon boils.

Doing so also reduces the amount of water you need and ever so slightly the amount of time you spend heating water.

 

[Scuba_Steve81]

Yup, what Martin said. My opinion, 1.5 gallons per hour boil off is more than what's required. I like to have mine around 0.6 to 0.7 gallons per hour for 7 to 14 gallon boils.

Doing so also reduces the amount of water you need and ever so slightly the amount of time you spend heating water.

I realize it's more than required, or desired. But how do you lessen it? I attempted to turn the burner down once it started to boil, but it is difficult to fine tune. Especially when you really can't see the flame.

It seems to go from full blast to off in about 3/4 of a turn of the burner propane valve

 

[Singletrack]

My last batch has a few grass clippings in it. Doesn't seem to have affected anything.

Just don't leave the grass in too long, because that can cause a hoppiness flavor.

 

[Yooper]

I realize it's more than required, or desired. But how do you lessen it? I attempted to turn the burner down once it started to boil, but it is difficult to fine tune. Especially when you really can't see the flame.

It seems to go from full blast to off in about 3/4 of a turn of the burner propane valve

That's hard, then. You want a rolling boil, so that the wort turns over. But you don't want to boil it so hard that you have excess maillard reactions (similar to caramelization).

I don't cover mine, as I don't even have a lid(!), but my boil off is about 1.25 gallons per hour, starting with a 12 gallon boil size to finish with 10.5 gallons (with what I leave behind in losses in my pump/chiller/etc).

I guess I would try to find the sweet spot after you reach a boil where you have a rolling boil, but not so that it's not jumping out of the pot.