What affects Original Gravity?

[Sneaker]

I just brewed my first partial mash, an oatmeal stout, from a Northern Brewer kit. The instructions say the the OG should be 1042. Mine was 1032. What factors determine the OG? What might I have done differently to make the gravity higher?

 

[JiveTurkey]

Full or partial boil?

 

[Orfy]

Any one or all of the following.

1. Better mash efficiency.
2. Better mixing of the wort before measuring.
3. Better use of the hydrometer.
4. Better control and measuring of volumes
5. Further reduction of volumes.

Probably others as well.

When you say OG do you mean into the fermenter or preboil?

 

[Edcculus]

Since it was partial mash, I'm assuming you just didn't mix well. Thats usually the biggest case with extract or partial mash kits.

 

[Sneaker]

JiveTurkey: It was a partial boil.

Orfy: I see. Lots of possibilities. I understand each item on your list, except #3. Are you saying it could it be operator error, or is there another "better" way to use the hydrometer?

 

[Sneaker]

Since it was partial mash, I'm assuming you just didn't mix well. Thats usually the biggest case with extract or partial mash kits.

Ah. So the OG could actually be higher that the reading I'm getting? Or is it indeed wasn't mixed well, I'm stuck with 1032?

 

[Orfy]

Ah. So the OG could actually be higher that the reading I'm getting? Or is it indeed wasn't mixed well, I'm stuck with 1032?

How long has it been in the fermenter.
You could give it a good mix and remeasure.

As for Hydrometer use.

You need to:
take a good sample which means mixing well before taking a sample.
ensure the sample is at the correct temperature or do the correct calculation
understand how to read it correctly.

My guess is lower than expected efficiency and not mixing well enough.

 

[TipsyDragon]

if your wort wasn't mixed well then your reading of 1032 is invalid and should be thrown out. as the yeast ferment they will do the job of mixing your wort for you and give you the proper amount of alcohol.

some times extract just sinks to the bottom and stays there. if you draw your hydrometer sample from the top you will get a false low reading. if you draw it from the bottom you will get a false high reading. i usually top off in my brew pot then whirlpool like mad. try to see how deep i can get the vortex to go. i then let it sit for 10 minutes to settle then take a reading. this helps mix your extract and collects all the trub in the middle of the pot making siphoning easier.