-20 Points

I just finished a Celebrator Doppelbock clone and checked the gravity.

After very carefully reading the hydrometer, I get 1.063 @ 75°.
The target OG is 1.080 - 1.085.

How the heck can I be 20 points below target?

Extract? All grain? Lots of variables. Maybe post the recipe, your method and other such important variables

Good point.

Sorry, I'm all grain. Here's the recipe:

Dark Munich Malt (global): 28oz
65L German dark crystal: 8oz
chocolate malt: 5oz
german pilsner malt: 12lb
Dextrin malt (carapils): 14oz

Infusion mash.

The grain bill was a little high for my setup, so I split it all in half. I was very careful measuring everything and I'm sure I would have realized it by now if I omitted something.

I'm not too confident about my thermometer. I actually use 3 or 4 different ones and go with which reading is most common. I'm wondering if my mash temp was too low during one of those two mashes, but 20 points? I don't know.

ALWAYS take a preboil gravity reading. This is recommended over and over on the forums in every single "First AG batch" thread and yet people always skip this. Had you done it, you could have added DME and hit your target.

Big grain bills are frequently trouble for efficiency, and the fact that you split it in half only increases the problem. Basically, you just weren't able to sparge enough.

Just settle for the fact that you made a bock instead of doppel... it will probably be delicious and rich. I don't like turning our beers into experiments after they're brewed, especially when the problem is gravity. If it comes to fixing diacetyl or acetaldehyde, that's another story.

On a big beer there is a much greater gravity change in a small efficiency miscalculation. I would not worry about your thermometer if you are using several and using the common readings. That should be pretty close.

There are several things that can affect your efficiency, such as planning wrong, poor crush, sparge method, etc.

As the above poster mentioned, it best to take preboil readings when you are starting out, so you can adjust with extract, or top off with more water if need be. Once you have several batches under your belt and can be confident in your equipment and process, you can probably safely enter an efficiency into your software and come very close.

My system is pretty dialed in, but I still make efficiency adjustments based on the grain bill size. For me, if the bill is less than 14#, I can usually get at least 78-80%. For 14-17# I plan for 75-78%. For 17-20# I use 70%. Anything greater I'll usually plan for 65%, but when it's bigger than 20# I'm usually doing some sort of partigyle.

I always aim low so I can be pleasantly surprised when my preboil gravity is a few points higher than expected.

I'd say the crush. It's something easy that can royally screw your eff. If you buy from a LHBS or online, its possible that their mill got a number of problems that would effect your crush. If someone bumped into it and changed the setting even a little bit it can mess it up (happened to me, but my LHBS gave me store credit cuz they noticed it after I left). Not to mention if someone milled items that they perhaps shouldn't (ie flaked items) it can be functioning but perhaps not well...when you rely on other people's crush you never know what you'll get. Bottom line. Which is why you should always QC the grains before leaving the store.

kanzimonson said:

ALWAYS take a preboil gravity reading. This is recommended over and over on the forums in every single "First AG batch" thread and yet people always skip this.

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How do you guys take preboil gravity readings? Do you siphon off enough sweet wort to fill a hydrometer jar, wait for it to cool to 60F and then take the reading? Or do you just take it and try to adjust for temperature?

Before I had a refractometer, I used to put a small kitchen pot in the freezer at the beginning of brew day. After I filled my kettle, I vigorously stirred it for a minute, then I'd draw off about 3-4oz, put it in the frozen pot, swirl for a minute or two, and it was usually around 70-80* at this point.

Before I had a refractometer

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A refractometer makes this so much easier. If you can find one of the ebay ones, they're only $30-40 and this way you can check at any spot you want to see how you're coming along (first runnings, sparges, pre-boil, post-boil, etc.). They don't work well for post-fermentation, but if you've got the money they can make understanding what things help efficiency in your system and what things don't help much a lot easier.

If you just finished it or if you did last night just boil up a couple pounds of extra light dme in a couple quarts of water for 15 min, cool then add it to the wart. I did this the day after I brewed up my first AG batch and it worked like a charm.

Wow, a lot of responses. Thanks all!

I've been doing a lot of thinking today and I have a few theories as to what may have happened.

I have to admit that I usually fly blind when it comes to this. I follow the recipe, follow my procedure, and cross my fingers. I am starting to see how this is bad and I'm going to have to take some steps to be a little bit more scientific about it. I need to get some software, learn it, and use it! I'm a hardcore Mac fan. I know there are a lot of options out there even for the Mac guys, does anyone have any suggestions about software?

Two brews ago I made a barely wine. I ran into a number of problems in that brew. There were times that I about scrapped it all. The most notable mistake, which may ironically be why my gravity was almost exactly right on target, was when my mash tun's mesh braid got clogged right when I started my sparge. Note that I had the same equipment, so I did the barley wine in two batches as well. In order to fix the stuck sparge, I had to pour my brew from bucket to bucket, through colanders and then again through sieves. Then I put the grain back into the mash tun, and ran the wort through my HLT. With fingers crossed, it all ran through and the grain filtered out the junk. The point to telling you about this is, I think it's possible that this messy process gave me a very efficient sparge.

This got me to thinking about what I may have done wrong with the sparge on this doppel. There's one thing that may be the culprit. I read somewhere that you should recirculate the runoff back through the mash tun until the wort starts to run clear. Well, I've been putting the first few quarts back into the HLT, so that I don't drill down through the grain bed creating a channel and clogging the sparge-out. It may be possible that by putting the thick, rich, sweet wort that first comes out back into the HLT is what caused the problem. The sparge water is sweetened, thereby making it less efficient in the sparging of the grain. I think that some of that sugar was left behind in the grain because I was actually not sparging with clear water. For the next brew, I'm going to carefully pour the first few quarts through a colander to add it gently back into the mash tun BEFORE I open up the HLT. Does anyone agree that this could be part of the problem?

bmantzey said:

I'm not too confident about my thermometer. I actually use 3 or 4 different ones and go with which reading is most common. I'm wondering if my mash temp was too low during one of those two mashes, but 20 points? I don't know.

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In my extract brews, I use a digital thermometer directly in my wort while wort chiller is doing it's thing. I've noticed that I get different temps depending on how deep I stick the needle in. I try to be consistent in the spot I take the temp, but I'm worried my wort is still too hot when pitching the yeast.

What is the desired location in wort to take temp - deeper down or closer to the surface? From the middle or to the sides of the pot?

So after reading all the posts I feel confident that it the answer lies in the splitting of the mash. For the same volume of water you are getting less sparging contact time with the grain bed because your sparge volume is split. I have a feeling your runnings at the end of the sparge were probably still pretty high gravity. I also have to agree with a previous poster who noted that they always recommend a pre-boil gravity measurement, I can't agree with that enough. Despite our best efforts I always see fluctuation in the mash performance, but there are lots of things you can do to bring that OG up. For instance I have run simultaneous boils before. What I mean is I have sparged to get my pre-boil volume, but realized by pre-boil gravity was low. I've taken the remaining runnings until I get down to 1.010 and boiled them down to concentrate them and then add them back to the primary boil. This isn't ideal, but its helped save my gravity before. I've also taken to planning 90 minute boils which gives me the ability to tweak my boil time to fix gravity issues.

bmantzey said:

This got me to thinking about what I may have done wrong with the sparge on this doppel. There's one thing that may be the culprit. I read somewhere that you should recirculate the runoff back through the mash tun until the wort starts to run clear. Well, I've been putting the first few quarts back into the HLT, so that I don't drill down through the grain bed creating a channel and clogging the sparge-out. It may be possible that by putting the thick, rich, sweet wort that first comes out back into the HLT is what caused the problem. The sparge water is sweetened, thereby making it less efficient in the sparging of the grain. I think that some of that sugar was left behind in the grain because I was actually not sparging with clear water. For the next brew, I'm going to carefully pour the first few quarts through a colander to add it gently back into the mash tun BEFORE I open up the HLT. Does anyone agree that this could be part of the problem?

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Yes don't do this. It would probably not account for missing by 20 points but it will reduce fly or batch sparging efficiency. The whole vorlauf thing is a little overrated anyway. Just maybe put the first quart back on top of the grain bed and start collecting wort. If a couple bits of grain come through they will drop out in the boil.

It is not clear if you are fly sparging or batch sparging. If you are fly sparging your efficiency will depend on sparge flow rate...slower = better efficiency.

The other use for a refractometer is to see if your mash is fully converted. Your grist with german pils, munich and chocolate might need more than 60 minutes to fully convert depending on your crush, stirring frequency etc. It is pretty easy to calculate the expected sugar content in the mash at 100% conversion and check your actual sugar content against expected before you start to sparge. If you are t 95% you might say close enough but if you are at 70% you would know you need to do something to fix the situation -- probably stir it some more and give it some more time...
Here is a link to an explanation of how to do the calculation:
http://www.braukaiser.com/wiki/index.php?title=Understanding_Efficiency

you are looking for the bit with the equations called Measuring Conversion Efficiency. Don't worry about the equations just use the table he kindly provided...