First all-grain - 3.5 gallon boil off??

[Rubes]

So the other night we made our third beer, which was our first all-grain. We got a 50 liter pot and a propane burner for the occasion. We decided to do BIAB since at the moment it's cheaper and easier than building a mash tun. The recipe was O Flannagain's stout, so we had 9.25 lbs of grain. I used two different calculators for water volume, one said to use 8.5 gallons and the other said 7.5. I decided to put 7.5 gallons into the pot, as I figured that would get us pretty much right on 5 gallons.

We had a problem from the beginning with the 5 gallon paint strainer bag not being nearly big enough (I didn't know we would be using a 50 liter pot when I bought a 5 gallon bag!) We made that work though by being creative, so after mashing and letting the bag drain and squeezing all the liquid out of it we still had close to the 7.5 gallons we started with. Then we boiled for an hour. We cooled it in 30-40 minutes by just leaving it outside and spraying the outside of the pot with a hose. It was below zero when we were brewing so it worked out pretty good. I was surprised that when we put it into the fermenter we only had about 4 gallons, maybe even a little less! How could we have boiled off 3.5 gallons?? The pot is more wide than it is tall, and it was also pretty cold outside. There was a lot of steam coming off the pot. Could these factors contribute to the high boil off rate? It was also at pretty much a full boil the entire time, once the hot break settled then I just it do its thing. Should I turn it down more and just let it simmer next time?

The OG of the 4 gallons was 1.056, and our target was 1.046 so I added water to the 5 gallon mark. The gravity is now 1.042. How significant is that differnece between our target gravity and our actual gravity? Will it be too diluted, or will it simply result in lower ABV? In any case it's fermenting away right now so we'll find out for sure in a few weeks.

Thanks

 

[jwags48]

well a couple points. you really shouldn't squeeze the grains. the grains do hold water. you might want to get a rubbermaid bev. cooler and mash in that. you don't have to have the hole set up with the fly sparge. what you do is put your mesh bag in cooler with grains and x amount of water.mash. then batch sparge...I think Charlie s' book has a chart for water amounts for different grain amounts, I think. back to your batch that had low volume. I use something like 9 gals for a 6-61/2 yield pre-boil...

 

[el_caro]

you really shouldn't squeeze the grains. the grains do hold water.

I think it is generally acceptable practice these days with BIAB to give the bag a good squeeze to extract as much liquid as reasonably possible.
The grains certainly do hold water and I feel there may be an error here in the preboil volume recorded as I cannot reconcile that mashing 9.25 lbs of grain resulted in no loss of water? If so that may account for the apparent boil off volume being high.

 

[BOBrob]

I have to agree with El Caro. How did you mash and for how long? What temp did you mash at? If you mash/boiled for an hour and then boiled wort for an hour you would loose around 2.5 gallon at a hard boil in the lower outside temps + one gallon for absorption would get the 3.5 loss. BIAB is more like steeping grains, which is hard to do with propane and still maintain a mash temp. of ...say 154F. Even guys with electric set ups use a pump to recirculate the water to maintain an even water temp during mash in. Just thinking out loud but I hope it helps. Cheers:rockin:

 

[beerman0001]

The 7.5 gal was for your pre boil volume. You still need to acount for how much the grain is going to soak up.

 

[DannyD]

If experienced that all grain requires allot of water! I usually use about 25 - 30 L of water and end up with 16L of post boil wort! All is explained by your high gravity.

And I also have one of those squat pots; they are very deceiving with volume estimation,

 

[Piratwolf]

I'm having a little trouble understanding some of the replies, but the OP's situation is no mystery.

I get an absorption rate of about .15 gal/# of grain. OP started w/ 7.5 gal to mash 9.25# of grain, which rounded off should yield about 6 gal pre-boil. Given a wide pot, roiling boil, and trub/hop/hot break loss, a yield of 4 gal is no big surprise.

As for missing your OG by 4 points, that's nothing to worry about at this stage. I'd guess almost nobody could detect the final difference.

What I've found is that every big change in my brew equipment changes my outcomes, so one of the keys to improving your beer is getting to know your process and equipment thoroughly! And, of course, to read HBT like a fiend . Good luck & brew strong!

 

[kh54s10]

The 7.5 gal was for your pre boil volume. You still need to acount for how much the grain is going to soak up.

+1

The grains hold a lot of water. I boil at a constant but low boil and start with about 7 gallons in the boil pot to end up with 5.25 - 5.5 gallons

 

[Fennis]

I've recently started doing BIAB. Its a learning process as my first try I ended up being way over because I used too much water--my pre-boil was something like 8.5 gallons and I ended up with almost 6 gallons and an undershot OG. My second attempt, I started with a little over 7 gallons and about 9 pounds of grain, and after the grains soaked up maybe a half gallon, I ended up with almost exactly 5 gallons after my boil, and I hit my OG dead on based on the calculations I had. It just takes trial and error. While it may not look like it, the grains will soak up some water. Also, you will lose a different amount of water based on how hard of a rolling boil you have and how high you run the burner. If you have the burner going just enough to keep the rolling boil instead of having the burner on a higher setting, you will not only burn through less fuel, but also less water.

 

[Rubes]

Thanks for all of the replies. From what it sounds like I think I lost over a gallon to grain absorption and the remainder to the boil. I turned the heat down when it started boiling but it was still pretty vigorous, I'll play with it some more next time. We'll be brewing Yooper's Pale Ale in the near future, maybe for that one I'll go with 9 gallons of water..

Also, I mashed for 60 minutes and was able to maintain 152-155 the whole time, and then I brought it up to 170 and stirred it around for 10 minutes at the end. I realized after that I should have maybe mashed for 90 minutes, but I seem to have got decent conversion regardless.