17 replies to this topic

[chadm75]

So this has happened to me on a number of occasions....I start with 6.5 gallons of pre-boil wort only to be left with about 4.5 gallons post-boil. When I was brewing with extract, I could add whatever amount of water to bring it back up to five gallons and not worry about it. But with all-grain, I've read not to do this. Any suggestions? Why is my evaporation rate so high? Thanks!

[BrewerGeorge]

Feel free to add water after the boil if necessary, as long as you're reasonably sure it's clean. Add it before chilling, especially, and the whole thing will still be hot enough to be sterile. Definitely add before pitching (or within just a few hours of pitching) and not after fermentation or you risk oxidation. It's really hard to get all the dissolved oxygen out of water. Before pitching, that dissolved oxygen is a good thing. Afterward, it will make it stale. That's probably the reasoning behind the negative comments you've heard before.Two gallons/hr is a bit high for boiloff, though. Turn down the heat a bit.

[MtnBrewer]

I would base my decision on whether or not to top up on gravity rather than volume. If your gravity is high then top up with enough water to dilute it to the correct gravity. If it's correct or low, then I would not top up at all.Also, it would be a good idea to measure your evaporation rate so that you can take that into account with your pre-boil volume.

[chadm75]

Feel free to add water after the boil if necessary, as long as you're reasonably sure it's clean. Add it before chilling, especially, and the whole thing will still be hot enough to be sterile.

Would this throw off my gravity numbers? Why can you add water to top-off with extract brewing and not all-grain?

[MtnBrewer]

Would this throw off my gravity numbers?

See my post above.

Why can you add water to top-off with extract brewing and not all-grain?

You can with all grain it's just that you usually don't need to. You design everything so that you come out with the right gravity at the end without topping off. With extract, particularly with a concentrated boil, you need to top off to dilute to the right gravity.

[chadm75]

I've got a 7 gallon brewpot that I fill with wort. I just can't believe my evaporation rate! I guess I need to bring to a boil and then reduce the heat just a tad.

[MtnBrewer]

I've got a 7 gallon brewpot that I fill with wort. I just can't believe my evaporation rate! I guess I need to bring to a boil and then reduce the heat just a tad.

Well, yeah there's no need to keep a raging boil going once you get it up to the boiling point. I cut my fire down quite a bit to maintain a good solid rolling boil but not a violent one.

[Fatman]

If you add water post-boil to try and fine tune your gravity or volume, it will affect your IBU's, though if it's a small amount it might not be noticeable.Keep track of your boil-off rate - I get 2-2.2 gal/hr in my 15 G pot and adjust your water accordingly in the mash and sparge.I worry more about my S.G. than volume, so I make a quick calculation pre-boil (and thus pre-hops) to make sure I'm on track to hit my gravity. If I'm going to be low, I boil longer, if I'm going to be high I add water. (and tweak the hops accordingly)Preboil gravity X Preboil volume = Postboil gravity X post boil volume and Preboil volume - boil time X boil-off rate = Postboil volume.One more good reason to get that refractometer - calculations are easier in Brix/Plato

[BrewerGeorge]

If you add water post-boil to try and fine tune your gravity or volume, it will affect your IBU's, though if it's a small amount it might not be noticeable.Keep track of your boil-off rate - I get 2-2.2 gal/hr in my 15 G pot and adjust your water accordingly in the mash and sparge.I worry more about my S.G. than volume, so I make a quick calculation pre-boil (and thus pre-hops) to make sure I'm on track to hit my gravity. If I'm going to be low, I boil longer, if I'm going to be high I add water. (and tweak the hops accordingly)Preboil gravity X Preboil volume = Postboil gravity X post boil volume and Preboil volume - boil time X boil-off rate = Postboil volume.One more good reason to get that refractometer - calculations are easier in Brix/Plato

You're right, it will affect IBU's. It will bring them back where they were planned to be.IBU's are a unit of concentration and follow the same equation you've listed above. If you boil down below the planned volume, gravity will go up but so will IBU's. You likely won't notice because the balance will still be the same. Similarly, if you dilute to get the OG you'd planned, you'll also be diluting the IBU's, still maintaining the balance.

[djinkc]

I haven't dealt with this problem in a while. But, IIRC you will get less utilization with a higher gravity wort. If I was stuck with this I would continually add to the boil to maintain volume and hopefully not screw up my IBUs. Of course at my place if I overshoot IBUs it's something I will happily deal with. With a post boil top off you're dealing with the opposite.I think the solution is to figure out how to get your boiloff rate matched to your system. That way you will hopefully hit the volume you want, with more importantly the OG you want.This is one of those things that us basement brewers can dial in pretty quickly since ambient conditions are fairly constant. I get 2 gal boiloff with ~ 18+ inch diameter - depends on if I go 70 or 90 min though. If you're getting that much with a keggle I would suggest cutting the flame a bit after reaching a boil.Hope that helps a bit.

[BrewerGeorge]

I haven't dealt with this problem in a while. But, IIRC you will get less utilization with a higher gravity wort. If I was stuck with this I would continually add to the boil to maintain volume and hopefully not screw up my IBUs. Of course at my place if I overshoot IBUs it's something I will happily deal with. With a post boil top off you're dealing with the opposite....

True, but the wort gravity is higher at the end - where hop utilization is low anyway.

[chadm75]

If I was stuck with this I would continually add to the boil to maintain volume and hopefully not screw up my IBUs. Of course at my place if I overshoot IBUs it's something I will happily deal with. With a post boil top off you're dealing with the opposite.

This is interesting! What about adding more water during the boil? Maybe at the 30 minute mark?

[Stout_fan]

First off, even though some regard it as a poor example, Bud brews and ferments at 1.080. Then they post fermentation water it down 50% to an effective 1.040 OG. Any off flavors will certainly show up in their brand of water.My Irish red is a 23 gal batch. I dial that into promash with a 13.5 gal wort size. PM bumps the hop addition as it utilization goes down as SG goes up. However in your case utilization, which occurs mostly in the first 30 minutes, probably isn't affected.Water away!

[chadm75]

First off, even though some regard it as a poor example, Bud brews and ferments at 1.080. Then they post fermentation water it down 50% to an effective 1.040 OG. Any off flavors will certainly show up in their brand of water.My Irish red is a 23 gal batch. I dial that into promash with a 13.5 gal wort size. PM bumps the hop addition as it utilization goes down as SG goes up. However in your case utilization, which occurs mostly in the first 30 minutes, probably isn't affected.Water away!

Would you recommend adding a little bit of water every few minutes into the boil or adding another gallon, let's say 30 minutes in? Or would it not matter?

[MtnBrewer]

Would you recommend adding a little bit of water every few minutes into the boil or adding another gallon, let's say 30 minutes in? Or would it not matter?

I think you're overthinking it. It doesn't really matter. But the first thing I'd try is cutting back on the flame to reduce your evaporation rate.