Hydrometer issues - User error?

[specialkayme]

For what it's worth, I've been using a hydrometer for 15 years. I'm not new to it. Had no issues with it . . . until recently.

I've never really measured my boil off rate. Instead I use an OG/FG calculator, and adjust for the starting/ending specific gravity to find the boil off rate. It's usually consistent, so no worries. I upgraded to an eBIAB setup, and so I have to find my boil off rate all over again. I did some tests to confirm, and thought I knew where I was.

Two batches ago I did a Honey Wheat. I measured a pre-boil SG of 1.032. Using my boil off rates, and the calculator, I should have had a post-boil SG of 1.043, and about 5.5 gal left in the kettle. When I finished, I had a little less than 5.5 gal (could be due to me not consistently dialing in the heating element) but an SG of 1.038. Or 0.005 gravity points off. A little confused, I moved on.

Last brew I did a pale ale. 6.5 gal in the kettle with a starting SG of 1.052. Post boil I should have had about 6 gal left, and an SG of 1.057. Instead the SG measured in at 1.042. Completely confused, I stirred up the wort and measured again, and it came at 1.048. Or between 0.015 and 0.009 gravity points off. Clearly something is wrong, as my SG wouldn't be dropping after doing a boil, with less volume post-boil.

The 1.032 and 1.052 measurements should be about right, as it's in line with my expected BHE. The post-boil gravity measurements, in combination with the post-boil volume, have me scratching my head. I'm assuming it's user error, but I don't know how I haven't messed up in the past 15 years but suddenly can't figure out how to read a hydrometer now.

All values were either taken at calibration temp, or were adjusted back to calibration temp.

So where am I being stupid?

 

[dmtaylor]

This is a case where I think I'd have to look over your shoulder, as what you describe seems right and unlikely to be so weird. Is your hydrometer cracked or paper slipping or something? I really can't say. Maybe pick up a second hydro and do double measurements to see if one is just wrong.

 

[specialkayme]

No cracks or paper slipping as far as I can tell. It also seems odd that the hydrometer is measuring close to what should be right both pre-boil and post fermentation, but not post-boil (the 1.038 batch I added honey that was planned after the reading, and it finished at 1.008; while with the 1.042 batch I added a pound of honey just because I ended so far off the mark, and it finished at 1.004 - of which I was not expecting it to finish that low but the taste confirmed it was very dry and not a misreading of the hydrometer). If the hydrometer was broken or the paper slipping, I should get distorted readings on all three, not just one.

I thought about picking up another hydrometer, because lets be honest I'm probably going to break this one at some point in time, but I'm doubtful it'll solve the issue. It has to be user error. I just can't figure out how.

 

[Rodent]

Instead the SG measured in at 1.042. Completely confused, I stirred up the wort and measured again, and it came at 1.048.

This is what catches my eye - are you sure you aren't victim to incomplete mixing or some kind of settling of the wort

I'm just grasping at rice hull chaff with this ...

 

[specialkayme]

are you sure you aren't victim to incomplete mixing or some kind of settling of the wort

In short, not really.

I always take my hydrometer readings with a beer thief. Even if I'm taking it from the kettle. Because I'm not trying to take readings from the top or the bottom of any vessel, but instead from the middle, I place the beer thief in the center of the mass and let it fill up. Not an exact science, but better than taking a reading from the bottom tube, or the top 2" of liquid.

Now, why would it produce accurate results for the past 15 years, but not the last 2 brews? eBIAB is new to the mix (well, technically those last two batches were runs #3 and #4 off the eBIAB set up, when #1 and #2 went without a hitch hydrometer wise), but I can't figure out why the electric heating element would cause a less consistent mixing of SG than a stove top unit. If anything I would imagine having the heating element inside the kettle would create a better mixing.

The reason why I always took readings from the center was to avoid sucking up hop material and proteins. I didn't want to take the SG of dissolved proteins. I suspect the difference between 1.042 and 1.048 was the difference in additional proteins and other materials that I stirred up. I suspect the 1.042 is the better measurement of the actual gravity.

But with either 1.048 or 1.042, how did I decrease SG from my pre-boil measurement, while also reducing volume? If it is a homogenization issue, that is a SIGNIFICANT homogenization problem, where the center is reading 1.042, and that would mean the rest of it would have to measure 1.072 in order to get the right calculated SG, all in 5 gallons of liquid sitting in a 15 gallon pot. But again, this is beer, not an oil/water mixture.

It's literally blowing my mind.

 

[AZCoolerBrewer]

I had a weird situation where my wort seemed to boil at 218 degrees. I was using my thermometer wrong. I think you have 3 things going on if I had to guess. The first is that the possible error for the hydrometer gets really big the hotter the wort you are testing is. Second, I think your E-BIAB has a much slower boil off rate then you are used to. When it comes to concentration and boil off, if you are less concentrated after boiling, you know that either your pre or post reading wasn’t accurate. Lastly, my experience has been that a refractometer is the best tool for making quick measurements during mash and boil.

 

[specialkayme]

The first is that the possible error for the hydrometer gets really big the hotter the wort you are testing is.

I understand the point you're trying to make, but I'm not sure I fully understand the application you're alluding to. I used a hydrometer temperature calculator to adjust the hydrometer reading to the temp it was taken at (https://www.brewersfriend.com/hydrometer-temp/). Are you saying that the hydrometer may need to be adjusted even more than the calculator would provide for?

Looking at the last batch, I had three SG measurements:
1. Pre-boil - taken at roughly 129 degrees - 1.052 (after adjusting for temp.)
2. Post-boil - taken at roughly 70 degrees - 1.042 (after adjusting for temp.)
3. Finishing gravity - taken at 66 degrees - 1.004 (no temp adjustment)

If the higher temp would push the SG reading outside the temp adjustment calculator's presumed range, shouldn't the pre-boil reading be more off than the post-boil or finishing gravity readings?

Second, I think your E-BIAB has a much slower boil off rate then you are used to.

Very much so. Plus I have a kettle condenser attached.

But I can eyeball what's going into the fermenter to get an idea of roughly what post-boil volume I have, then use the calculators based on SG readings to get a more accurate boil-off rate. The problem is when I fill a 6.5 gallon carboy almost up to the rim, but the calculator says I should have 5 gallons in the carboy. It isn't adding up.

Lastly, my experience has been that a refractometer is the best tool for making quick measurements during mash and boil.

I've heard that before. Can you tell me why a refractomerter is a better tool? I have one for testing moisture content in honey, and it's a complete pain to maintain. It can break easily, is expensive, and needs constant calibration before each use (which in the honey refractometer case isn't that hard, I can calibrate with olive oil, but I can't do that with a beer refractometer). Hydrometers are easy, cheap, and don't require calibration before each use. Or what else am I not fully grasping?

 

[AZCoolerBrewer]

I never wanted to check my gravity during the mash or boil, but then I wanted to one day but didn’t want to have to cool my wort all the way down to 60 degrees, so I cooled it to around a hundred and twenty degrees because I was concerned the temp shock would break it. Even with the temp correction I got a really off number that seemed impossible to me and that was the last time I tried to measure with my hydrometer at temperatures that are greater than 10-15 degrees above my calibration temp.

Certainly a refractometer is more expensive. My wife bought me a really nice one for my birthday. I checked the zero calibration when I got it and when I did a DME SHaME beer I checked the cal and it was on within 2 points. For wort readings, it has never had numbers that I suspect as inaccurate. I think it could break if I dropped it, but the measurements are pretty low impact and so I feel pretty safe using it without breaking it, knock on wood. Since it uses so little wort for testing, I just take a spoonful of wort and put it in a small ramekin which pretty much instantly cools the wort to where I can get an accurate reading.