Missed My OG the last two batches!! What am doing wrong?

[BigEasy43]

The last two batches I did had an OG of 1.040 and should have been 1.052 and would like to know what I am doing wrong. I have a coleman cooler setup with a Bazooka screen inside. Is it that my pre boil amount of water is off? Too much water I mean? I let the grain sit in the cooler for the 60mins at the correct temp. Just like to know what I could be doing wrong as I am coming out with light beer and would like to get the correct ABV.

 

[beskone]

How are you sparging? batch, fly, no sparge? how are you calculating? what's your boil off?

 

[BigEasy43]

Batching sparging and checking my OG with hydrometer. Boil off no idea as I thinking this is one of my issues. Not having the correct amount of wort in kettle before boil?

 

[McKnuckle]

Get a grip, man! If you want to understand your numbers, you have to know your numbers.

There are two points on brew day where gravity comes into play:

1) At the end of the mash/sparge, called pre-boil gravity; and
2) At the end of the boil, called original gravity or OG.

If you know the first, you can to some degree control the second. The more evaporation during the boil, the more concentrated your wort, and the higher the gravity. If you formulate a recipe for 1.5 gallons of evaporation and you only boil off 1 gallon, your OG will be lower. You can boil for longer to compensate if you like, then adjust for your next recipe.

Here is a boil-off calculator:
http://www.brewersfriend.com/dilution-and-boiloff-gravity-calculator/

On the front end of things is your mash efficiency - how much sugar you got out of the grains, and how much wort you recovered from the cooler/mash tun. Lots of things affect those steps but I'll let others address them.

 

[doug293cz]

Get a grip, man! If you want to understand your numbers, you have to know your numbers.

...

Exactly. And we can't help you if you don't give us the necessary numbers. The measurements you need to take and report, in order to get help with efficiency problems, are:

• Grain bill weight. Preferably verified by you, not just trusting you got what you ordered.
• Strike water volume.
• First runnings volume.
• First runnings SG.
• Sparge water volume, separately for each sparge step.
• Pre-boil volume.
• Pre-boil SG, after thorough mixing of all runnings.
• Post-boil volume.
• Post-boil SG (i.e. OG.)

Temperatures at which all volumes are measured should also be reported, so that thermal expansion compensation can be done. It makes a difference.

All hydrometer measurements should be done within 20˚F of the hydrometer's calibration temperature, and then compensated for the actual measurement temperature.

Most people don't take a first runnings SG, but it can be used to calculate your conversion efficiency. Since mash efficiency is conversion efficiency times lauter efficiency, it is necessary to be able to determine conversion efficiency to diagnose issues with mash efficiency (i.e. is it a conversion or lautering problem.)

Accuracy of measurements is critical. The calculated efficiencies are no more reliable than the measurements on which they are based.

Brew on

 

[JimRausch]

Well said, Doug!
And very concise too.

 

[brewpool]

Agree with the above. When I started brewing all grain I plugged in as many numbers into Beersmith as I could (tun size, boil off rate, etc) . I still missed OG by 10 and 8 points (low) on my first two batches. For my system (large 52 qt rectangular cooler) and grain crush at my LHBS I get a 62% efficiency vs the stock 70% Beersmith assumes.

You have to dial in your system and the only way to do that is to measure along the way. Since I've dialed in my setup, I've nailed OG within a point or two for every batch since.

 

[martinlarosa]

Besides what doug requested, for your next batch you should stop draining the mash when you hit your pre boil target gravity. You'll get less beer, but it will be the beer you want. For that you'd need to know the evaporation rate of your kettle. So that you can say I want OG of 1.055 and the evaporation rate is X, then you can go to a calculator and calculate the preboild gravity, let's say maybe 1.045.

This is just so your next batch is accurate although not in volume. That's what I always do, don't worry about the final volume but about the target beer. Next time I adjust the efficiency issues to get more beer.

That said, measure what this guys are requesting as well so they can help you find out the main source of the problem.

 

[kh54s10]

Besides what doug requested, for your next batch you should stop draining the mash when you hit your pre boil target gravity. You'll get less beer, but it will be the beer you want. For that you'd need to know the evaporation rate of your kettle. So that you can say I want OG of 1.055 and the evaporation rate is X, then you can go to a calculator and calculate the preboild gravity, let's say maybe 1.045.

This is just so your next batch is accurate although not in volume. That's what I always do, don't worry about the final volume but about the target beer. Next time I adjust the efficiency issues to get more beer.

That said, measure what this guys are requesting as well so they can help you find out the main source of the problem.

The advice in red will not help in correcting anything. It will just make that batch correct in gravity.

As already stated there are many things that contribute to getting the proper OG.

One thing is that the recipe must be made to achieve the proper gravity. If you have a recipe calculated to for 85% efficiency and your system will only give you 65% you will never get there.

Most calculators will let you set the expected efficiency.