Low O.G. on a recipe converted from all grain

I recently was given an all grain recipe for an interesting-sounding AG scotch ale. Since I don't have the gear for all-grain yet, I read up on converting recipes and thought I had a handle on it. The recommendations I saw were .6 lbs DME to each pound of base malt.

To be sure I didn't mess up my math, I entered the all grain recipe in BeerAlchemy, then created a DME Extract version. I kept an eye on the estimated OG and made sure it was the same on the two recipes. Since the recipe was given to me as percentages, I aimed to keep the percentages the same; this may have been a mistake, I now realize.

So the grain bill I was given was:

SG: 1.068
FG: 1.016
IBUs: 26

82.4% 2 Row - 11.5 lb
12.6% Crystal 40 − 1 lb 12 oz
4.2% Melanoidin Malt - 9.3 oz
0.4% Carafa II - .9 oz
0.2% Peated Malt - .5 oz

Mash at 155°F for 60 minutes, with a 90 minute boil.

My converted recipe, targeting a 5.5 gallon batch:

7lb 10oz Light DME
1 lb 2.6 oz Crystal 40
6.2 oz Melanoidin
0.6 oz Carafa II
0.2 oz Peated Malt

Steeped grains at ~160°F, did a partial boil of 3.5 gallons for 90 minutes and had enough boiled water to top off to 5.5 gallons.

The two volumes of water were combined in carboy, then the carboy was agitated for five minutes to mix and oxygenate. Then I pulled a sample and my hydrometer read 1.057.

The beer itself is fermenting merrily, but I'm wondering what I missed that my OG would be off by 11 points. Any thoughts would be appreciated.

Maybe the recipe you followed was for a 5 gallon batch, and you did a 5.5 gallon batch? That would explain most of the discrepancy.

Was the original AG recipe for 5 gallons, or 5.5?

The all grain recipe was given as percentages of various malts; it's from a recently-closed microbrewery. BeerAlchemy was estimating the gravity based on 5.5 gallons of water, so I don't *think* that'd be the issue.

Incidentally, the percentages listed for the AG version are what I was given. The weights are estimated to give an OG of 1.068 for a 5.5 gallon batch.

I aimed to keep the percentages the same; this may have been a mistake, I now realize.

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Right. You should have kept the quantities for the specialty grains the same and converted the 2-row to extract.

david_42 said:

Right. You should have kept the quantities for the specialty grains the same and converted the 2-row to extract.

Click to expand...

That's what I thought I did; the conversion factor I used (from here was .6 lb DME to each pound grain; that comes out to 6.9 pounds DME. BeerAlchemy said my OG would be too low, so I added DME until I was back at 1.068 OG. Despite that, I came in at 1.057.

Doing more research, I came across a different article on conversion, which recommends eight pounds of DME.

I hope I'm not being needlessly obtuse here; I'm trying to figure out what I missed in my conversion.