OG Higher Than Expected

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Well-Known Member
Oct 1, 2007
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Chicago Burbs
Here's another noob efficiency question, but kind of in reverse. My first AG foray was a pale ale and I nailed all the numbers from Beersmith dead on with respect to mashing, volumes, and gravities. I just made my second AG batch today...a Guinness clone. Here's my grain bill and expected OG using 75% efficiency (same as my first batch) from Beersmith:

Amount Item % or IBU
8.0 oz Rice Hulls (0.0 SRM) 5.44 %
6 lbs Pale Malt, Maris Otter (3.0 SRM) 65.32 %
1 lbs 8.0 oz Barley, Flaked (1.7 SRM) 16.33 %
12.0 oz Roasted Barley (500.0 SRM) 8.16 %
4.0 oz British Crystal Malt - 55L (55.0 SRM) 2.72 %
3.0 oz Acid Malt (3.0 SRM) 2.02 %
9.2 lbs. TOTAL

Est Original Gravity: 1.046 SG
Est Final Gravity: 1.013 SG
Estimated Alcohol by Vol: 4.36 %
Bitterness: 39.7 IBU
Est Color: 30.6 SRM

The grain was mashed with 3 gallons of water at 150°F for 90 minutes (seemed like a long time, but that's what the recipe called for). Then I batch sparged twice with 2.5 gallons each of 168°F water. Total wort collected was just over 6.5 gallons. This was then boiled for 90 minutes.

I ended up with 5 gallons of wort with an OG of 1.057...11 points higher than expected. Going back into Beersmith and messing around with variables the only thing my noob self could find that would have caused it would have been an efficiency of 90%. Is this even possible? Could it have been the long mash time? I lautered very slowly, about 2-2.5 hours total drain time between then three. Could this have caused the high OG?

I ended up adding half a gallon of water to 4.5 gallons of this wort to end up with 1.048...not quite what I was aiming for , but much closer. I just want to know what borked my OG so I can compensate for it next time.
And you're complaining? Actually, it does seem rather high. Are you sure you measured everything out correctly, measured the gravity right and at the right temperature?

I'm new to this board, so I don't know what the prevailing opinions are. Personally, I think it looks a bit complicated for only a second brew and I would suggest that you build up the complexity as you go along, otherwise you will never get a feel for the effect of any one ingredient in the taste profile. And rice? Actually, you would probably have got an equally good brew by dropping everything bar the pale malt and roast barley and bumping up the quantities accordingly - the best (as opposed to the biggest) commercial brewers would never use that level of adjunct material, which are often employed to reduce costs rather than improve flavour.

As a matter of interest, this is the recipe from my last stout:

7lb. Maris Otter
8oz. crystal malt
8oz. torrefied wheat
1lb. roast barley
8 oz. demerara sugar
3 0z. Fuggles hops

which all came out to 1047. I thought this was a bit on the low side, but my equipment does seem to impose limits on the gravity I get when atempting to brew comparatively strong beers. No matter, it tasted good and that was all that concerned me. Incidentally, the torrefied wheat was only there for head retention.

All that aside, it strikes me you have actually done really well for somebody only two brews into the hobby. The gravity (barring unlikely major cock-ups on the measuring front) would indicate that you've got mashing taped. Hope it tastes good!
Sluggo... this is amazing... I just joined this board, just finished putting an intro message, opened a thread and BANG... you're dealing with the exact same problem I was dealing with when I first went All Grain a few months back.

To me, your grain bill has good balance... the thing you need to realize is that you just learned the efficiency level your equipment is capable of producing. I was doing the same thing... I'm using Beertools, was plugging in 75% because it was suggested as a number to start with, and kept crafting grain bills that were not working out.

My OG was not working out and, even more alarming, my final gravities were not working out... too high. My efficiency value was coming in about about 68-69%.

Finally, after doing a couple batches, paying attention to my proceedures, I found the problem was with crushing the grains.... believe it or not I wasn't crushing those babies enought. I have a Corona mill, notorious for over crushing grain and producing alot of flour, so I was trying to be conservative.

Once I started crushing my grains more my efficiency shot up to 90%. In a 10 gallon batch that allowed me to reduce my grain bill by 4-5 Pounds of grain, because I was compensating for the lack of efficiency with additional grain. This was a true break through for me.

So, when I work with Beertools crafting a new grain bill, the first thing I do is change the default of 75% to 90%, because that is what my equipment (and yours) is capable of. Then, the bill that I put together is appropriate for my setup.

I've been dead on with OG ever since.... hope this long winded answer helps.
I've had this same "problem" since I started brewing. I don't think I've ever had an efficiency below the 90's. So, unless my LHBS's scale is off and he's giving me too much grain, I chalk it up to good crush, water pH on the lower end, and fly-sparging. Just out of curiosity, what's your water pH?
Yes, it is possible. Long times, thin mash & low temperature, all of these factors lead to higher efficiency and a highly fermentable wort.

An interesting read on the types of Guinness produced.
Oh I wouldn't say I'm complaining. Far from it. It just surprised me that this batch came out around 90% while my first batch, using the same equipment, procedures, etc. was at 75-76%. I measured the gravity about 10 times as it cooled from 82° to 68°. Using temp comps they all came in between 1.056 and 1.058.

My first thought was that I mashed my first batch for 60 minutes vs. 90 minutes for this one and that was the difference. I can't think of anything else I did differently. I bought my grain precrushed at the LHBS, but that's also the same place I bought the ingredients for my first batch...I suppose that's another variable I don't have control over. I can use this as an excuse to get a grain mill now. :D

Just out of curiosity, what's your water pH?

I didn't measure that. The local water supply is kinda crappy and tends to change during different seasons because the city pumps it from deep wells and mixes it with water from the river. Even though it was "rated" near the top for flavor in municipal water supplies (who the hell does this) I like no flavor in my water. I started with distilled and added 1g/gal of calcium carbonate.