What did I do wrong?

[reim0027]

So, I'm brewing a Russian Imperial Stout. I have had efficiencies in the 60's. So, I try a different setting on the grain mill at my LHBS. I thought I set it at 0.032. I have already calibrated my equipment and know how much dead space my mash tun has.

So, brewday comes and everything starts off great. I nail my mash temp. But, my preboil gravity is WAY off. My target (according to BeerSmith) is 1.094. I hit a whopping 1.048. On top of it, my preboil volume was 1/2 gallon over.

I can't let this stand for a RIS. So, I do some gravity unit calculations and realize I need about 5.2 pounds of DME. I go to the LHBS and pick up 6 pounds of dark DME. I put that into the pot and boiled until I hit my target OG. I ended up doing a 2 hour boil (hops for 60 minutes).

I was left with 6 gallons of wort at an OG of 1.100. The color was good too.

What happened to crash my preboil gravity? Could I have messed up the crush (wrong setting at LHBS)?

Here's my Beersmith Recipe and notes:

Type: All Grain
Date: 5/15/2011
Batch Size: 5.50 gal
Boil Size: 7.16 gal
Boil Time: 60 min
Brewhouse Efficiency: 60.00

Ingredients

Amount Item Type % or IBU
16.50 lb Pale Malt (2 Row) UK (3.0 SRM) Grain 65.22 %
2.20 lb Barley, Torrefied (1.7 SRM) Grain 8.70 %
2.20 lb Caramel/Crystal Malt - 40L (40.0 SRM) Grain 8.70 %
2.20 lb Oats, Flaked (1.0 SRM) Grain 8.70 %
0.55 lb Black (Patent) Malt (500.0 SRM) Grain 2.17 %
0.55 lb Chocolate Malt (450.0 SRM) Grain 2.17 %
2.47 oz Magnum [14.50 %] (60 min) Hops 75.9 IBU
1.10 lb Corn Sugar (Dextrose) (0.0 SRM) Sugar 4.35 %
1 Pkgs Irish Ale (Wyeast Labs #1084) [Starter 1 gallon]

Mash: 30.25 quarts at 164.5 F, target mash temp 152 F

Batch Sparge: Add 2.59 of water at 168 F
Poured water in, mixed very well, let sit for 5 minutes

Notes

5/12: Yeast starter = OG 1.049, Briess Dark DME. Pitched Activator (4 hours post smacking) @75 degrees.

5/15
Mash temp: 152
Post mash temp 149.5
First runnings 1.049
Second runnings 1.029
Preboil gravity 1.048
Preboil volume 7.67 gallons -- too high, goal 7.16 gallons
Added 6# dark DME, will sig affect color, but get my total gravity units where
I want them to be. Bummer.
120 minute boil to get to 1.100 OG
6 gallons at the end of the boil.
Pitched yeast at 66 F

 

[RLinNH]

Great Thread!!! I went through the same thing with a RIS not 8 Months ago. I am anxious to see th replies as I am used to Mid 80-high 80% eff. Ratings. I jumped through my arse just to get the OG up to 1.100.

 

[badmajon]

(deleted misread post)

 

[nostalgia]

I'm going to guess the small sparge has a lot to do with it. You're mashing with 7 1/2 gallons of water and batch sparging with only 2 1/2. This is necessary to hit your boil volume correctly, but will result in leaving a lot of sugar in the mash tun.

When I do a really big beer like an RIS, I always do it as a parti-gyle. I use more grain up front and calculate a much lower efficiency for the first beer, since I'm only using the first runnings and a very small sparge.

I generally calculate for 58% efficiency on the first beer. Here's an example:

Recipe Specifications
--------------------------
Batch Size: 5.50 gal      
Boil Size: 7.03 gal
Estimated OG: 1.108 SG
Estimated Color: 63.5 SRM
Estimated IBU: 53.1 IBU
Brewhouse Efficiency: 58.00 %
Boil Time: 60 Minutes

Ingredients:
------------
Amount        Item                                      Type         % or IBU      
25.00 lb      Pale Malt (2 Row) UK (Golden Promise) (3.0Grain        84.75 %       
1.50 lb       Black Barley (Stout) (500.0 SRM)          Grain        5.08 %        
1.00 lb       Caramunich Malt (56.0 SRM)                Grain        3.39 %        
1.00 lb       Special B Malt (148.0 SRM)                Grain        3.39 %        
0.50 lb       Chocolate Malt (350.0 SRM)                Grain        1.69 %        
0.50 lb       Pale Chocolate Malt (200.0 SRM)           Grain        1.69 %        
2.00 oz       Horizon [8.50 %]  (60 min)                Hops         37.7 IBU      
2.00 oz       Goldings, East Kent [5.00 %]  (15 min)    Hops         11.0 IBU      
2.00 oz       Goldings, East Kent [5.00 %]  (5 min)     Hops         4.4 IBU

Mash Schedule: Single Infusion, Medium Body, Batch Sparge
Total Grain Weight: 29.50 lb
----------------------------
Single Infusion, Medium Body, Batch Sparge
Step Time     Name               Description                         Step Temp     
60 min        Mash In            Add 36.88 qt of water at 165.9 F    154.0 F

-Joe

 

[reim0027]

I thought the sparge seemed a little low. So, for my next batch, I'll lower my effeciency and count mainly on my first runnings to make my beer.

But, my first runnings SG was very low. My first runnings had half of the gravity units I needed for my preboil.

The only thing I can think of is the crush.

 

[nostalgia]

Did you measure the gravity your first runnings before mixing with the sparge? You can check your mash efficiency with the chart here.

It should be close to 100%.

-Joe

 

[nostalgia]

And yes, if your first runnings are way off, there aren't too many options aside from crush or a *ton* of doughballs.

-Joe

 

[twigboy2000]

There's also possibility of the thermometer being way off and being outside the temp range for covnersion in your mash. I'd check that too.

-chuck

 

[MazdaMatt]

Did you make my dumb panic-inducing mistake and take the OG reading while the pre-boil wort was still hot from the mash?

 

[reim0027]

My thermometer is brand new. It is this one.

I used a calibrated ATC refractometer to measure the preboil gravity. I then checked it with a hydrometer, adjusting for temperature. Same numbers.

I thought I mixed it very well. I mixed it more than any of my other brews. It must have been my crush. But, I'll pay close attention to my mixing as well.

Thanks for the ideas guys. I will likely do a 90 minute boil for my high gravity brews and mix very very very well. No more messing with my LHBS's grain mill.