Inconsistent hydrometer reading

[PDevlin75]

Good morning!

I brewed a batch whose BG was estimated in BeerSmith to be 1.048. I poured a sample into my hydrometer test tube, and it said that the BG was 1.030 and the temp was 102 degrees. Adjusting for calibration, it would have been 1.036

I then put the hydrometer in my boil kettle and checked again... This time, it read as 1.040 at 122 to give me an adjusted 1.051

I'm inclined to go with the boil kettle reading, as that makes me feel better that I was closer to my numbers. But why the difference, do you think? Volume?

Thanks,
-Pete

 

[Yooper]

Good morning!

I brewed a batch whose BG was estimated in BeerSmith to be 1.048. I poured a sample into my hydrometer test tube, and it said that the BG was 1.030 and the temp was 102 degrees. Adjusting for calibration, it would have been 1.036

I then put the hydrometer in my boil kettle and checked again... This time, it read as 1.040 at 122 to give me an adjusted 1.051

I'm inclined to go with the boil kettle reading, as that makes me feel better that I was closer to my numbers. But why the difference, do you think? Volume?

Thanks,
-Pete

It's temperature. Over 100 degrees, the readings just aren't accurate. Cool a sample to 80 or below, then take the reading. You can then adjust for calibration at that time.

Stir the wort well first, to make sure there is no stratification, and then take the sample and cool it to under 90 (preferably under 80) before taking the reading and it will be far more accurate.

 

[Oginme]

It's temperature. Over 100 degrees, the readings just aren't accurate. Cool a sample to 80 or below, then take the reading. You can then adjust for calibration at that time.

Stir the wort well first, to make sure there is no stratification, and then take the sample and cool it to under 90 (preferably under 80) before taking the reading and it will be far more accurate.

Just to add to Yooper's comment above, as you are taking the gravity reading of a sample which is much higher than ambient temperature, that sample temperature is changing.

I take a sanitized quart canning jar and put about 400 cc of hot wort in, cover and place in a bowl with water and ice. This usually cools the sample down to room temperature in less than 5 minutes and I am able to take the gravity reading much closer to the calibration temperature of the hydrometer.

 

[PDevlin75]

Thank you both for the info! So if I'm left to infer this correctly, perhaps the reading in the tube at 102 degrees is still closer to the truth than the boil kettle at 120? In which case, my BG was pretty low. I've refrigerated my sample tube before - Just didn't this time. Oh, well.

Just the same, my OG reading was higher than it should have been, and I took that after the wort had been cooled down to below 80 - But that's another question in a different thread.

Well, whatever - The OG was good, so I'm sure the beer will be fine either way! Just working the bugs out of my routine. Might just see if good ol' Santa can bring me a refractometer this year!

Thanks!

 

[Calder]

Are you sure everything was mixed in the original sample. Sugars/extract tend to stratify, and the liquid at the top can have a lot lower gravity than the liquid at the bottom. As the wort heats up, it improves mixing.

 

[PDevlin75]

I dunked a measuring cup into the kettle to pull out the sample for the tube. So no, I can't say that THAT was mixed very well... But I did stir the kettle a bit before I tested that. You could be right, as I did pull a sample off of the top.

I think it might be as stated before in regards to temp...

Judging by my OG, my efficiency was probably better than predicted. I was using BeerSmith, and my equipment profile still had the default setting of 75%. It seems as though I might have had something in the low 80s instead.

My volumes were spot on, so I have to assume that perhaps I just didn't let it cool enough to get an accurate BG reading. Or maybe mixing the sugars like you said.

Either way, all is well in fermentation-land!