Original Gravity problem

Anyone ever have problems with inexplicably low original gravities? With my last 3 batches, the gravity has been coming up 25%-50% short. (My expectations are based on appendix 11 of the 3rd edition of the Complete Joy of Homebrewing). Obviously, I can just add some more fermentables to get the gravity I want, but I'd like to find out what's causing the problem.


Relevant Details:
I usually boil about 2.5 gallons for a 5 gallon batch;
I mix and aerate the wort before taking a sample;
My samples are usually around 70 degrees when I take a reading, and I adjust the reading accordingly;
I've checked the hydrometer, and it's fine;
I've had this problem with both LME and DME;
These have been all extract, so the answer can't be that I'm messing up the mash;


Again, I realize that this isn't hard to remedy, but does anyone have any suggestions for why I might have this problem now? All of my batches before these last three have been pretty much right on.

Thanks for any suggestions, I appreciate any advice.

Cheers!
-Mike

Can you give a recipe with how much ingredients you started with?

We need numbers, because it is impossible for an extract recipe to be off on the original gravity, unless the wrong amount of water and/or extract is used. Or the calculations (expectations) are wrong.

Yeah, if you are using extract, your numbers should be dead on... in my last AG I used 7lbs of Maris Otter and got 1.042... with 5.25 gallons going to the fermenter. If I calculated that correctly, that is in the high 70's%. That was my best ever
Brewpilot

After having gravity problems with a couple of partial-mash batches, I decided to "dumb it down" for my most recent batch, to try to figure out what's going on. This is probably the best example to provide:

I used 5lbs of DME for a five gallon batch. According to The Complete Joy of Homebrewing, that should yield about 1.042-1.046. My reading was 1.033.

Again, I've double and triple checked the hydrometer and all other measurements. I've made batches with extract from different sources to try to rule out the possibility that I'm just getting some bad extract.

I realize that this can be easily remedied by adding more fermentables, but if anyone has any idea what else could be causing this, I'd appreciate your advice.

Thanks!
-Mike

Are you sure you ended up with 5 gallons? How are you measuring the volume in your fermenter? My other thought is how is the DME packaged? Is it generic and packaged by the LHBS or a name brand? Are they ripping you off and putting less in the bag?

I was just reading this thread: http://homebrewtalk.com/showthread.php?t=16247
and was wondering if you were pouring water into the fermenter to top up the volume after the boil and then checking the gravity? If you pour it in and don't shake it up, you will get a falsely low OG. Wort is heavier than water, so the water will kinda "float" on top of you don't mix it.

Brewsmith said:

I was just reading this thread: http://homebrewtalk.com/showthread.php?t=16247
and was wondering if you were pouring water into the fermenter to top up the volume after the boil and then checking the gravity? If you pour it in and don't shake it up, you will get a falsely low OG. Wort is heavier than water, so the water will kinda "float" on top of you don't mix it.

Click to expand...

I've done that. Unfortunately, I did it with a batch that I split into two fermenters, so I ended up with one awesome, incredibly malty, full-bodied beer, and a second that was decidedly LESS SO.

Nothing wrong with a Small beer. Years ago, people would batch sparge and ferment each run separately.

Brewsmith said:

My other thought is how is the DME packaged? Is it generic and packaged by the LHBS or a name brand? Are they ripping you off and putting less in the bag?

Click to expand...

Its interesting that you said that. I checked my two 1lb bags I used in my brew yesterday with the new scale I bought. One was 0.25oz. short and the other was 0.5oz. short.

Bastards. I'm going to have to start buying the 5lb package so I can measure out 2lb properly.


I clean my equipment with Straight A. I've noticed that if I have some residue of it on my hydrometer, I get false low readings.

Brewsmith said:

Are you sure you ended up with 5 gallons? How are you measuring the volume in your fermenter? My other thought is how is the DME packaged? Is it generic and packaged by the LHBS or a name brand? Are they ripping you off and putting less in the bag?

Click to expand...

Yes, five gallons. I use a little guage on the side of the fermenter. After having the problem with the first batch, I checked this to make sure it is accurate. The marking is a little bit off, but no more than a few cups.

Interesting note on the DME, though. It's generic, and I haven't double-checked the weight on it. I'm pretty sure the LHBS owner is on the level (really cool, helpful guy), but that's definitely something to investigate.

On the water/wort mix question, I'm pretty sure that it's mixed well when I take a sample, because I really slosh it around to aerate the wort. Perhaps next time, I'll use my siphon to get a sample from the middle, rather than from the top with a measuring cup . . .

Thanks to you and everyone else for your suggestions! In the meantime, I'll stop worrying about it, relax, and have a homebrew.

Cheers,
-Mike

unfortunately water + malt extract = OG. One of those two components is off. Assuming you are using anything resembling potable water it has to be the extract. Either his scale is off or there is something wrong with his stock.