Full wort boil

[dbogcpa]

Just did my first full wort boil but only started out with 5 gallons of water in pot and didn't top off fermenter. Two questions:

1 - only have about 4 1/4 gallons in fermenter, what effect will this have on final product, and
2 - how much water should I start with in pot to end up with 5 gallons after boil is completed?

[6thstreetbrewer]

1. Your beer will be gone sooner...but it will be little stronger.
2. Depends on your system, how hard you boil, probably altitude and ambient temps. I start out with 7.5 gals. and after about a 90 min. boil I end up close to 6 gals. Do it several times, take notes and you'll figure it out.

[ApresSkiBrewer]

1 - If you hit your OG, your beer should be just fine. If its higher than expected, then yes, you're beer may be stronger than expected. Not to worry, drink, and brew again.
2 - +1 dbog... it entirely depends on your evaporation rate. That can be anywhere from 8% to 20% depending on how hard you boild. Start with 15%... and adjust your pre boil volume accordingly, to finish with 5-5.5 gallons of beer.

I only have a 7.5 gallon pot, and even when I watch it like a hawk, and start with 6.5-6.75 gallons of wort (right around 5-5.5 finished post boil), I never quite get a full 5 gallons of finished beer, after transfers, and trub and all that.

IMO it is more important to hit your recipes numbers, than your final volume... so if you are doing that, then don't sweat it too too much.

[Neuron_Theory]

Besides being a waste of propane, is there anything wrong with doing a boil of just water to determine the evaporation rate of your system?

[ApresSkiBrewer]

The evaporation rate of just water and wort might be a little different, but I bet it gets you in the ballpark.

You wouldn't have to do a full 60 minutes... although you could. If you wanted, you could go with 5 gallons of water, for thirty minutes. if you finished with 4.625 gallons... that would be 7.5%.... and then you would just double that to get your hourly evaporation rate. (15%) Which is right about where mine clocks in (sometimes higher).

I would lean to doing the full hour though, it might be a little more accurate. Just remember that evap. rate is always calculated by the hour....

But that would be a good question. Does the evaporation rate change because of the Specific gravity of the liquid being boiled? Would a higher gravity wort evaporate more/less? Sounds like a Doc, Jamil, Palmer, Tastey question to me.

[Neuron_Theory]

But that would be a good question. Does the evaporation rate change because of the Specific gravity of the liquid being boiled? Would a higher gravity wort evaporate more/less? Sounds like a Doc, Jamil, Palmer, Tastey question to me.

That was my real question I guess. I am thinking it shouldn't matter on the gravity. 212 degrees is 212 degrees and that's where water boils and evaporates.

[Mylo]

But that would be a good question. Does the evaporation rate change because of the Specific gravity of the liquid being boiled? Would a higher gravity wort evaporate more/less? Sounds like a Doc, Jamil, Palmer, Tastey question to me.

It might be true that gravity has some role in the boil off rate - but the other factors that significantly affect it - degree of vi-gar-ousness of boil, surface area of the top of the wort, relative humidity, and amount of wind across the wort - will affect it much, much more. The relative gravity isn't much of a factor next to those other factors. Not anything worth considering, anyway.


Mylo

[ApresSkiBrewer]

Valid point(s) Mylo.

It's harder to bring 7 gallons of wort to boil though... than 7 gallons of water right? anyway, I think the other factors that Mylo listed play more of a role.

In the winter (now) in the brewshed... my evap. rate is more like 20%, because it is so dry... I believe... and only 30-40 in there.