Author Topic: Attenuation  (Read 1396 times)

Offline maltesebrewing

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Attenuation
« on: September 19, 2011, 09:23:09 AM »
Hopefully I'm making an obvious mistake that you all can help me clear up.  I was shooting for a wee heavy scotch that turned out wee light. The recipe I followed was:

10 lbs 2 row
2 lbs crystal 60
2 lbs munich
1 lb wheat
1 lb crystal 120
1/2 peat smoked malt

1.5 EKG 60 min
.5 Willamette 30
.5 cascade 5 min
Irish Moss at 10min

The recipe said I should have hit 1.085 - I hit 1.062.  I mashed at 140 for 20 min then up to 155 then 162 in a keg mash tun.  Lautered about 6.5 gal @ 170 of wort from a batch sparge for a 5 gal batch.  Boiled for 60 min chilled then aerated by pouring the wort back and forth twice.  Pitched 1 vial of White Labs scotch yeast directly into the wort.  The batch bubbled its butt off for about 5-6 days then slowed but continued to bubble.  When I went to move it to the secondary I checked the SG and it only dropped to 1.026.  It seems to be tasting ok but according to the software I'm using, I'm looking at a 4.4 ABV when I should be staring at 7+.  Where did I go wrong?

Offline denny

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Re: Attenuation
« Reply #1 on: September 19, 2011, 09:46:54 AM »
First of all, that's a very complex recipe for a wee heavy...and personally, the thought of peated malt in it makes me shudder!  Personal opinions aside, you would have had to have had nearly 100% efficiency to hit the gravity you were going for.  Given 3 lb. of crystal (should be none in a wee heavy), I'm not surprised at the lack of attenuation.  Plus you didn't do a starter.
Life begins at 60.....1.060, that is!

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Offline bluesman

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Re: Attenuation
« Reply #2 on: September 19, 2011, 10:02:54 AM »
Did you check your pre-boil gravity? What was your mash pH? 3lbs of crystal malt is a lot and will add quite a bit of unfermentable dextrins.  I would scale that back quite a bit on the next recipe.

I agree with Denny on making a yeast starter. This is a very important part of making good quality beer. Go to mrmalty.com to estimate the required starter for your next batch.
« Last Edit: September 19, 2011, 10:04:40 AM by bluesman »
Ron Price

Online dmtaylor

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Re: Attenuation
« Reply #3 on: September 19, 2011, 10:36:09 AM »
There's a lot going on here that can be fixed next time you make this:

1) Check the crush -- it's the number one reason for poor extract efficiency.  Folks say you need to "crush until you're scared" of it becoming pure flour which is impossible to sparge -- that's pretty much what I do.  But, like Denny says, with that grain bill you'd still have had to get around 100% efficiency to hit your planned OG.  So in that case...

2) You didn't sparge enough or boil enough.  It takes a lot of sparge water to rinse all the sugars out of that much grain, and it takes a lot of time to boil all that extra sparge water down.  Next time, sparge enough to plan for at least a 105-minute boil -- that's what I do for Scotch ale.  Two full hours or more would be even better if you don't mind the "waste" of time and energy.

3) 155 F is too high of a rest temperature.  If you want a high gravity beer to finish at anything other than a relatively high final gravity, you need to keep that mash temperature down to 150 F or even lower.

4) You used too much crystal malt.  Crystal malt has a lot of unfermentable sugar.  Bring that down to maybe half as much and you'll be in better shape.

5) Not enough yeast.  With a really big beer, you need to make a really big yeast starter.  Pitching straight unstarted vials is never a great idea, but especially so with big beers.

Fix those five things, and I can virtually guarantee your success in the future.   ;)
Dave

"This is grain, which any fool can eat, but for which the Lord intended a more divine means of consumption. Let us give praise to our Maker, and glory to His bounty, by learning about... BEER!" - Friar Tuck (Robin Hood - Prince of Thieves)

Online mtnrockhopper

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Re: Attenuation
« Reply #4 on: September 19, 2011, 10:50:50 AM »
First of all, that's a very complex recipe for a wee heavy...and personally, the thought of peated malt in it makes me shudder!  Personal opinions aside, you would have had to have had nearly 100% efficiency to hit the gravity you were going for.  Given 3 lb. of crystal (should be none in a wee heavy), I'm not surprised at the lack of attenuation.  Plus you didn't do a starter.

I'm not sure how your calculating this, but even at 70% mash efficiency I'm calculating an OG of 1.080 with this grain bill. 100% efficiency would bring it to 1.115.

To the OP: where did you get this recipe from? And how long have you been batch sparging and what efficiencies have you been getting? I'm just wondering if this is unusual for your experience or if it is your first time batch sparging.

1.062 to 1.026 is 58% attenuation which is low but maybe not outrageous considering the lack of starter, high gravity, and high amount of crystal malt.

And I don't know anyone who says 'crush until you're scared'. My grain gets barely cracked, far from flour.
Jimmy K

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Offline tomsawyer

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Re: Attenuation
« Reply #5 on: September 19, 2011, 11:25:37 AM »
Looks like you only got around 55% efficiency.  This is a little low, although you typically expect a lower efficiency with a big beer.  I generally get 75% on a 1.050 beer, I expect barely 70% on a bigger beer unless I count on a longer boil time/larger preboil volume.  I agree that you most likely had a problem with crush that contributed to the lower efficiency.  I'd also mash longer than 20min at 140F, I think the beta amylase is slower than the alpha.  Your recipe with 18% crystal was already going to give a high level of residual sugars so the high temp mash step was probably overkill.

I just brewed a Scottish 80/- that started at 1.060 and finished at 1.020, so our attenuations aren't far off.  I did a long boil on mine so I expected the lower attenuation.  We aren't that much over the Scottish 80/- specs (a few points over on both OG and FG) so I don't think the beers are going to be cloyingly sweet.  I just bottled mine and the FG sample tasted pretty good.
Lennie
Hannibal, MO

Offline bluesman

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Re: Attenuation
« Reply #6 on: September 19, 2011, 11:43:55 AM »
Can you give us a detailed mashing procedure including crush, Water profile. mash pH, etc...

Have you calibrated your thermometer and hydrometer?

With these details, we may be able to narrow in on a solution.
Ron Price

Offline denny

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Re: Attenuation
« Reply #7 on: September 19, 2011, 12:25:21 PM »

I'm not sure how your calculating this, but even at 70% mash efficiency I'm calculating an OG of 1.080 with this grain bill. 100% efficiency would bring it to 1.115.

Off the top of my head!  Using Promash, I get 1.072 at 73% effieicny, which is much closer to what you got.

And I don't know anyone who says 'crush until you're scared'. My grain gets barely cracked, far from flour.

Well, I say it, for one.
Life begins at 60.....1.060, that is!

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Offline bonjour

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Re: Attenuation
« Reply #8 on: September 19, 2011, 01:29:58 PM »
Top of my head says just over 1.060 for OG,  (10lbs will typically give you 1.050)
FG, with the crystal and the 155 mash, 1.025 +/- is about what I'd expect. 

the 1/2 oz of smoke (I hope that's ounces, not pounds)(I'd use Rauch malt, not peated) may give you a very low smoke in the aroma  (the yeast will also do it).
The correct amout of smoke in a Strong Scotch or Scottish ale is where you are asking, "is the smoke?"  If you say "That is smoke!" you have too much.

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Re: Attenuation
« Reply #9 on: September 19, 2011, 02:26:27 PM »
I'm with Fred and Denny on the peat smoked malt.  A half ounce of peat smoke per 5 gallons is PLENTY, perhaps even too much.  I used the equivalent of a half ounce in my last batch and it was still too strong.  So maybe a quarter ounce is even plenty.  But a half pound!?  Blecch!!!
Dave

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Offline tubercle

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Re: Attenuation
« Reply #10 on: September 19, 2011, 02:51:30 PM »


And I don't know anyone who says 'crush until you're scared'. My grain gets barely cracked, far from flour.

Well, I say it, for one.

 I actually "crush 'till you're stupid". I take it down to the scared level and then close it up another .001 or so. No stuck grain beds to speak of.
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Offline tomsawyer

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Re: Attenuation
« Reply #11 on: September 20, 2011, 08:24:48 AM »
I actually "crush 'till you're stupid". I take it down to the scared level and then close it up another .001 or so. No stuck grain beds to speak of.

We can tell.
Lennie
Hannibal, MO

Offline tubercle

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Re: Attenuation
« Reply #12 on: September 20, 2011, 05:00:04 PM »
I actually "crush 'till you're stupid". I take it down to the scared level and then close it up another .001 or so. No stuck grain beds to speak of.

We can tell.

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Offline oscarvan

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Re: Attenuation
« Reply #13 on: September 21, 2011, 03:20:33 AM »
If it was mine I would have let it sit on the yeast longer..... And, indeed less Crystal....and a little more base.
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Offline Kit B

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Re: Attenuation
« Reply #14 on: September 21, 2011, 08:28:26 AM »

I'm not sure how your calculating this, but even at 70% mash efficiency I'm calculating an OG of 1.080 with this grain bill. 100% efficiency would bring it to 1.115.

Off the top of my head!  Using Promash, I get 1.072 at 73% effieicny, which is much closer to what you got.

And I don't know anyone who says 'crush until you're scared'. My grain gets barely cracked, far from flour.

Well, I say it, for one.

And, I say it, for two.
Barley Crusher mill with .028 roller settings.
But, I always condition my malt.
« Last Edit: September 21, 2011, 08:30:16 AM by Kit B »
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