Original gravity problem--too low?

I'm having a gravity issue: three straight brews have wound up with lower-than-expected OG, all by about 4-8 GU. I'm an extract brewer which I always understood would mean missing the target gravity wouldn't be an issue. The first 2 brews were extract with steeping grains, and I'm pretty sure I hadn't stirred/aerated before taking the OG reading. The 3rd was my first partial mash, a pumpkin ale where I didn't figure pumpkin sugars into the OG, but expected to get some from mashing the canned pumpkin. That OG after stirring and aerating was 1.062, and expected was at least 1.068. Is there some reason I can't think of for having low OGs? Thanks.

Peter

Primary: pumpkin ale
Secondary: imperial brown ale
Bottle conditioning: American pale
Drinking: summer ale, IPA, double IPA

What recipes are you using? Are you sure the target OG is right? Also, are you sure you are using enough Extract? How are you measuring it?

For clarification, this is the recipe for the aforementioned pumpkin ale.

6 lbs extra light LME
1 lb dark brown sugar
1 lb 6 row malt
1 lb crystal 60 malt
8 oz wheat malt
8 oz special roast malt
1 lb rice hulls

60 oz canned plain pumpkin (two 30-oz cans) mashed with grains--no whole pumpkins available right now

1 oz fuggles 60`
1 oz hallertau 30`
1 oz fuggles 5`

1.5 tsp cinnamon
1.5 tsp allspice
1.5 tsp nutmeg
1 tsp ginger
0.5 tsp ground cloves
1 Tbsp vanilla extract

Nottingham ale dry yeast

OG 1.068 (not counting for pumpkin sugars)
FG: ~ 1.016
IBU: ~21
ABV ~6.9%

>What recipes are you using? Are you sure the target OG is right? Also, are you sure >you are using enough Extract? How are you measuring it?

The pumpkin recipe is above. The other 2 were an American pale, and an imperial brown ale. The target OG I calculated myself, but also entered into beercalculus at hopville.com and got the same gravity. The extract is liquid pilsen malt from a 33-lb jug, measured with a digital scale bought from a HB store. (except the pale--that one was canned Breiss ME) Could the scale be off?

Let me preface my post by saying I'm not a partial mash master -- I only did one partial mash before going all grain.

That being said, when I enter those ingredients into Promash, it tells me that I need an 80% efficiency to reach 1.068. That's probably part of your problem. If you were getting even 70%, you'd lose 2 points, and if you only had 60% efficiency you'd be down to 1.064.

I wonder if you need more enzymes from the two row to convert the specialty malts. Once again, I'm not a partial mash expert, so I don't know.

What temp are you doing your partial mashes at? How are you measuring the temp?

Sometimes Extract doesn't give you the full amount either -- it's not common, but it does happen. I'd calibrate your hydro and make sure it isn't measuring low either.

Whenever I see something like this in my process, I go through and make sure all my instruments are measured/calibrated right -- more often then you'd imagine, that finds the problem for me.

If you are doing partial boils, you may not be getting your top off water mixed well with wort.

I've checked my hydrometer, and it checks out. As does the scale. I think the efficiency may be the culprit. I tried my level best to keep the mast at 150 for 1 hr, but may not have been so lucky. What concerns me is that I had low readings for the 2 brews prior, where no mash was attempted. I even made sure the grains I was steeping would give me fermentables without a mash.

eaglehoo said:

I've checked my hydrometer, and it checks out. As does the scale. I think the efficiency may be the culprit. I tried my level best to keep the mast at 150 for 1 hr, but may not have been so lucky. What concerns me is that I had low readings for the 2 brews prior, where no mash was attempted. I even made sure the grains I was steeping would give me fermentables without a mash.

Click to expand...

Are you doing full or partial boils?

What temperature did you take your measurement at?