Egregious boil off

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Dave Warner
Posts: 78
Joined: Thu Aug 20, 2009 3:01 pm

Egregious boil off

Post by Dave Warner »

I've completed my converted keg brew rig with bayou classic sp10 burners using a 20 psi regulator.

I preboil my first 1/2 batch sparge while I'm sparging/vorlaufing the second half. I boil for 90 minutes.

Every batch I've done on this set up has yielded .5-1.25 gallons less than expected in the brew kettle. I've been formulating for 7 gallons, expecting about 1.5 gallon boil off, but I'm ending up with close to 4.5gallons in the kettle before I lose some to hoses/cold break in the counterflow chiller.

Anybody else notice 2.5 gallon boil off in a converted keg for a 90 minute boil?? :(

Is my burner overkill? I try and turn it down to a rolling boil once the initial foam subsides (30 minutes or so), but there is limited adjustment between the gas ball valve (pretty much all or nothing) and the air intake. I do have a needle valve for the direct fired MLT, but I've never had a need to use it to keep my mash temp. Should I swap them out?
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Bill Lawrence
Posts: 374
Joined: Tue Jun 27, 2006 8:18 am

Re: Egregious boil off

Post by Bill Lawrence »

Well, I also use converted kegs and that sounds about right in terms of evaporation. The rate of evaporation is dictated by the surface area of the liquid exposed to the air, not so much the heat coming off your burners (although you loose more when doing a hard boil just because you effectively present more liquid surface area to the atmosphere). Put another way, given the same volume of liquid, if the boiler is taller, you'll lose less to evaporation than you would with a shorter, wider boiler. None of that however makes a damn bit of difference in terms of beer quality. Anytime you go to a new system, you need to figure out (by trial and error) how your system is going to perform in terms of evaporation rate and extract efficiency.

Of course, I have no blessed clue as to what the hell I'm doing but here is my basic methodology. I do primarily 5 gallon batches and I always boil for 1 1/2 hours (which I recommend by the way). I have a notch carved into my mash paddle which tells me how much liquid I need to collect pre-boil to yield 5 gallons of finished beer (and I figured this out via trial and error as noted above). I also know that I'm going to get approximately 23 gravity points per pound of grain used in my system, determined again via trial and error and accounting for all losses from whatever source. Once I am done sparging (and I batch sparge in my system incidentally) I just make sure to collect the requisite amount of wort before beginning the boil. Once I get the stuff boiling, I pull a sample and see where I am in terms of specific gravity. I know from experience that I can multiply my initial reading by 1.33 and hit my ending gravity every time. If for whatever reason I don't hit my predicted initial gravity, I just boil a little longer until I do. I don't add any hops until 60 minutes to shut down so I don't need to worry about changes in hop utilization when I find I need to do this.

Now if you ask around, you'll quickly learn that many in the club just laugh when watching me brew so take all this for what it's worth. One of the major tricks to this hobby is to learn that getting really good extraction rates is not the key to making good beer but getting consistent extraction rates is. Once you learn to hit your numbers then you can screw around with your formulations to get your beer to taste the way you want it to. Actually, I like the fact that I get a fairly high rate of evaporation during the boil. First of all, it allows me to better control ending specific gravity if I end up missing low and secondly if I want to, I can boil down some of the first runnings to create alot of melonodin reactions which can really add interest to the finished beer, depending on the style.
Remember, brewers make wort, only yeast make beer
Dave Warner
Posts: 78
Joined: Thu Aug 20, 2009 3:01 pm

Re: Egregious boil off

Post by Dave Warner »

Thanks Bill. My chicken with the head cut off brewing would make yours look positively Zen.

I guess it's more art than engineering.

I've only done 4 all grain batches so far and only 2 where I started grinding my own grains so I have a lot of trial and error left to go.

This last batch I double-milled the grains, got a great filter bed and better extraction, so I shouldn't be afraid/perturbed to formulate even bigger boils.
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Bill Lawrence
Posts: 374
Joined: Tue Jun 27, 2006 8:18 am

Re: Egregious boil off

Post by Bill Lawrence »

Well, here is what I would do if I were you to figure out how your particular system works. Set your mill to the recommended gap setting and don't change it. The Limbo is coming up in a couple of months so brew a best bitter using 10 lbs of grain (in my system, if God is smiling on me I would end up with something like a 1.046 to 1.048 wort with an ending volume of 5 gallons) that way you'll be making an entry and learn something at the same time. You should already know how much liquid you need at the start of the boil to end up with the required 5 gallons at the end. Do a single infusion mash, boil for 90 minutes and see what happens. Measure your gravity at the beginning of the boil and at the end and write it all down.

You now know how many gravity points per pound per gallon you get (for instance if you end up with a 1.048 wort you know you get 24 points per pound). Also, if you take ending gravity minus 1 divided by beginning gravity minus 1 you can now predict pretty accurately what your ending gravity will be once you know your pre-boil gravity by just multipying it by the factor you just calculated. Now you are in a position to tweek recipes you get from others for your system or to accurately predict your numbers from formulations you gin up yourself. Also, if it looks like you are going to miss your beginning gravity because your pre-boil gravity is low, you can do something about it (ie. boil longer or add some DME). There are a few things that effect efficienty from batch to batch and with some experience you will learn what they are and adjust for them in the recipe. The whole trick with this is to do everything the same every time and if you feel you need to make adjustments, change only one variable at a time so you can keep track of what is going on. The only thing I have noticed in my system is that when you scale up to bigger beers the increase in grain required is not strictly linear. For instance, I need just a bit more than twice the grain to do a 1.080 beer than I would for a 1.040 beer but you'll figure that out also with time.

Finally, don't believe all the crap you will hear from people concerning their efficiency. Just because some brewer tells you that they get 95% efficiency doesn't mean nature was kind to them if you know what I mean. If they really got that (which I seriously doubt) they are almost surely extracting a bunch of tannins during the sparge and their beer is suffering because of it. The aim here is to make the best beer possible, not to insinuate that your stuff drags the ground because you got 90%+ extraction efficiency. :D
Remember, brewers make wort, only yeast make beer
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