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Frenchtom 01-22-2013 10:05 AM

Volume target of pre-boil wort
 
Hello guys - If I am shooting for 5 gallons of post boil wort how much pre-boil wort should I start with? I know there is no one correct amount as there are so many variables but I am looking for order-of-magnitude numbers here. Should it be 6 gallons, 8 gallons, 10 gallons?

Thanks,
Frenchtom

CastleHollow 01-22-2013 10:15 AM

It's a function of your evaporation rate. I usually lose about a gallon an hour, so my pre-wort boil is typically about 6.5-7 gallons

Bobby_M 01-22-2013 04:22 PM

I start with about 7 to hit 5.5 in 60 minutes of boil.

weirdboy 01-22-2013 04:25 PM

Mine is right around 1 gallon/hour so for me that would be 6 gallons pre-boil, although I usually fudge in another quart to account for transfer losses after the boil.

BarlimanButterbur 01-22-2013 04:26 PM

I usually do 6.5g to hit 5.5g after 60 minutes. That way I can usually get about 5g into the fermenter. Remember that this means you need gravity points and IBUs for about 5.5g.

mgr_stl 01-22-2013 04:27 PM

I just boiled a batch last weekend, and I was shooting for 5 gallons post-boil. I boiled 6, but ended up a little short. 6.2 gallons would have done it for me.

DocScott 01-22-2013 04:28 PM

You can figure this out easily for your system... Boil a few gallons of water for 15 or 30 minutes. Measure final volume. Multiply the amount boiled off by 4 (for 15 minute boil) or 2 (for 30 min boil). This will give a reasonable estimate for your set up in terms of boil off per hour

My system is about 1gallon/hr

LandoLincoln 01-22-2013 04:33 PM

Quote:

Originally Posted by Frenchtom (Post 4812150)
Hello guys - If I am shooting for 5 gallons of post boil wort how much pre-boil wort should I start with? I know there is no one correct amount as there are so many variables but I am looking for order-of-magnitude numbers here. Should it be 6 gallons, 8 gallons, 10 gallons?

Thanks,
Frenchtom

This is the only good way to get the answer to this question:

Carefully measure exactly 5 gallons of water into your boil kettle. Bring it up to boil, then start a 60 minute timer. Once it's done boiling for 60 minutes, cool it down and then measure the water again. This is your evaporation rate for a 60 minute boil.

mdgagne 01-22-2013 04:37 PM

Do you want 5 gallons post-boil, 5 gallons into the fermenter, or 5 gallons into bottles/keg? There are volume losses all over the place that you can consider.

1. Boil-off, anywhere from 10-25% depending on kettle, heat source ,etc
2. Cooling loses (4% I think). Boil hot wort takes up 4% more space than 65ish degree wort.
3. Hop absorption and kettle losses. This is the volume lost in hops, hot, and cold break in your kettle. I'm not going to try to estimate this one, it varies depending on the amount and type of hops, amount of cold break, and your kettle configuration.
4. Trub losses each time you rack your beer. Volume lost to trub after primary fermentation. I would bet 1/8 to 1/2 of a gallon is a wide estimate on this.

There are probably more, but I think I hit all of the major losses. If you take good notes on your first couple batches you'll have a good idea on the losses in your process and you can adjust your pre-boil volume accordingly.

With all that being said, based on my process I shoot for about 7 gallons pre-boil volume. Typically this yields 5.5 into the fermenter and a full 5 gallons of finished beer (I almost never secondary). I adjust up or down depending on the length of boil, amount of hops, and gravity of the beer (more beer = more trub loss in my experience).

Hope this helps.

m00se 01-22-2013 04:59 PM

I did my first all grain batch this weekend and ended up with more wort than I had expected. I started with 6.5gal for a 60 min boil hoping to end with 5.5gal. Sticking to the recipe, I only boiled for 60min and thinking maybe I should've boiled a little more to bring the volume down. My 6 gal carboy is filled up almost to the top.


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