Hydrometer weirdness

[DVCNick]

5gal Batch today:

Preboil: about 6.8 gallons: 1.060
Postboil: about 5.8 gallons: 1.059??

Temp was probably slightly warm for the first and slightly cool for the second, but according to the chart, this should still only impact it .001 each way, so even if it was a .002 swing this seems very weird to me. I was expecting around 1.070 post boil.

Is there anything obvious that could have caused this?

 

[RPh_Guy]

Is there anything obvious that could have caused this?

Misreading the hydrometer, or improperly mixed wort.

 

[BobBailey]

If you topped off with water before the post boil reading you didn't get a good mix. Other than that. you either had a bunch of break material/hop residue in your later sample, misread the hydrometer or relied on temperature conversion tables for the samples. After a very few degrees from calibration temperature, the tables lose accuracy rapidly.

Simple physics dictates that the gravity will be adversely proportionate to the volume, so if the volume decreases, the gravity will increase.

 

[AZCoolerBrewer]

When impossible things happen, you have to figure out where the error came from. I used the glass thermometer from my kit and it was saying that wort boils at 218 degrees. I trust my instruments so I tried to figure out how wort could boil at such a high temperature. After a discussion, I learned that at my altitude wort boils at right around 208 degrees. Someone later told me that a glass thermometer can’t be put into the hot liquid past the line marked on it or it messes up the reading. Anyways, it’s impossible to get less of a concentration of sugars after boiling off a gallon of wort. I think at higher temperatures the correction for hydrometers starts to break down. I responded fairly recently to a guy on here that had a very similar situation. As keep it simple of a brewer I am, I love the refractometer that my wife bought me for my birthday. It’s really great for measurements when the wort is boiling because you can very easily cool a couple a few drops of wort while it’s more difficult to cool 6 oz. of boiling wort.

 

[DVCNick]

Well I still had the post boil sample, so I let it come to exactly the zero'd temp on the chart and was still getting the same reading.

I took the sample from the ball valve port on the brew kettle for both. The preboil sample was right after I finished sparging, and of course the first part of the runoff is likely the highest concentration of sugars and then toward the end it is running much closer to clear. I didn't stir it after sparging prior to getting the preboil sample from the port (near the bottom of course)

Is there any way the sugars could have stayed layered and I got a preboil sample that wasn't representative of the average if it was stirred up?

 

[DVCNick]

Also I guess mis-reading is always possible, but I've been using it for several months now and feel comfortable with it... though if all other possibilities are exhausted you have to assume what remains is true.

 

[BobBailey]

Now it's easy to see what happened. Taking the pre boil sample from the bottom of the kettle is the key. The wort wasn't mixed so you sampled the first runnings. There had to be a simple explanation. You can't defy the laws of physics.

 

[DVCNick]

Ah. So just give the kettle a good stir before taking that sample and starting the boil?

I think I might be having a similar issue with bottling sugar, but that might be a different thread.

 

[BobBailey]

Yep, a stirring motion from bottom to top works well.
When bottling it's best to put the warm priming solution in the bucket first and then the beer. Once the beer is transferred a gentle stir, again with some bottom to top motion. I always gave another gentle stir after every 8 to 10 bottles just to be sure.

 

[DVCNick]

Thanks.
On the bottling, I'm doing everything you said except for the stir after every 8-10 bottles, and still, probably at least 20% of my bottles have a noticeably weird carbonation level, either low or high. Seems like more of the ones that are off are low. I guess I will start giving the bucket a quick stir when I stop about that often to cap.
I figured a lot of stirring would lead to too much oxygen exposure.

 

[BobBailey]

Just be gentle when you stir.

 

[balrog]

Oh ya stir. Gently, sure, but stir. The higher a concentration diff between two liquids, generally the harder/longer to really thoroughly and truly mix them. Think dumping LME into water. I've seen concentration striation in priming sugar added to empty/halffull/full priming bucket. Stir that stuff. Gently. But stir long time.

 

[RPh_Guy]

The wort is already oxidized. Stir it as vigorously as you want.

 

[ncbrewer]

The wort is already oxidized. Stir it as vigorously as you want.

This is opposite from everything I've ever read - I try very hard not to splash. Could you elaborate?

 

[AZCoolerBrewer]

I think he is saying that because we are not using closed transfers like cool brewers that we’re already screwed and to not even bother with trying to prevent exposure until you consider being a cool kid too.

 

[RPh_Guy]

This is opposite from everything I've ever read - I try very hard not to splash. Could you elaborate?

Here are some brulosophy experiments. Note that the results are not trending toward significance.

http://brulosophy.com/2014/11/18/is-hot-side-aeration-fact-or-fiction-exbeeriment-results/

http://brulosophy.com/2016/12/26/ho...uating-the-impact-of-age-exbeeriment-results/

The science is that your strike water and mash technique already introduce more than enough oxygen to fully oxidize the wort on the hot side.

LODO techniques are designed to combat this and preserve the fresh malt flavor.
http://www.lowoxygenbrewing.com/brewing-science-and-technology/the-reality-of-oxygen-ingress/

This LODO topic invites insecure brewers to troll because they don't want to be told their standard methods are inadequate.
The truth is that great beer can be made either way.
Bottom line: Stirring the wort won't hurt one bit if you are using standard brewing practice.

Cheers

 

[AZCoolerBrewer]

I think that they are talking about stirring in the sugar for bottle conditioning. That’s why I thought that you were being sarcastic when you said “stir as much as you want”. I know that excessive oxygen can be added in the bottling bucket from experience and so would not recommend vigorously stirring in priming solution in the bottling bucket. This Brülosophy exBeeriment does show that oxygen exposure happens during bottling and that minimizing exposure may be warranted.

http://brulosophy.com/2018/03/12/th...oning-on-new-england-ipa-exbeeriment-results/

 

[RPh_Guy]

Sorry, I got mixed up ...

I thought they were responding to this since the thread was about mismatched pre- and post-boil s.g.

So just give the kettle a good stir before taking that sample and starting the boil?

Definitely avoid vigorous stirring/splashing in the bottling bucket