Question Regarding OG - Recipe vs. Actual

I brewed this recipe about a week ago. The recipe states the OG for a 5 gallon batch should be 1.055. I measured 1.048.

It's an extract with steeped grains - partial boil. The only thing I did different was I started with a 5 gallon boil and added ~ 1.25 gallons of top of water after to get my amount in fermenter to 5 gallons.

Why the discrepancy?

 

well 2 things come to mind... Extract is tough to mix so you could have gotten a diluted gravity sample. Or, 2, your boil off rate wasn't what you thought it would be and you added too much water to get you up to 5 gallons thus dropping the gravity.

 

This was what I had post-boil before transferring to carboy and topping off.

 

It sounds like you tried to do a full boil, but didn't compensate for boil off. Besides maybe turning the heat down to a gently rolling boil to decrease boil off amount.

 

Exactly. It was certainly a hybrid process. I wanted to do a full boil but decided to play it safe and just boil at 5 and top off. I figured that would be better than boiling 3 and topping off.

 

With extract and steeping grains, the measurement is probably off due to uneven mixing of the wort and top off water. Using g extract it is almost impossible to miss the OG unless the volumes are way off.


Extract provides a certain amount of sugars. Boil off rate has nothing to do with it. If you boil off 1 gallon or two, then top off to 5 gallons, you still will have the exact same amount of sugar.


Relax, you are OK.

 

Oh, I'm not sweating it.... Just trying to learn.

Appreciate the responses.

 

I second what Beergolf said, boil off rate has nothing at all to do with OG with an extract kit.
Topped to 5 gallons it doesn't matter how you got there. the OG will still be the same.
I am leaning toward the sample not quite mixed well enough so reading low, did you compensate your reading for temp? that might add a couple of points meaning you aren't that far off.

 

Well, this was one mistake I learned from. I chilled the wort down to 70 F with my immersion chiller. Then I transferred and topped off the fermenter and took my sample.

I didn't get around to measuring OG until maybe 30 minutes later and I didn't check the temp.

It was out in my garage and it was pretty chilly that day.... Low 40's I think. So I can't factor in the temp.

Could that make that big of a difference?

 

Depending on the temp you hydrometer is calibrated for. Some are 60 degrees and some ar 68. It would not make a big difference since you were pretty close temp wise. Maybe a point ot two.

 

If the wort was colder than the hydrometer's calibrated temperature, the reading will be HIGHER than the actual gravity, since cooler wort is more dense than warmer wort. Being under temperature would make your measured gravity higher, not lower, than your true gravity.

Most likely this is a mixing issue, as mentioned above. Even stirring well after topping up with water can still result in unevenly mixed wort and hence inaccurate gravity readings.

 

Yeah, I have to stir them together for at least some 3 minutes to get an accurate reading. Here's a hydrometer correction program that's come in handy; http://www.brewheads.com/gravcorrect.php