Pre-boil gravity vs OG

[smccarter]

I've been noticing something recently and wanted to post here to see if it's normal, or if it's something that I need to resolve somehow...

I really never took a pre-boil gravity reading until recently. Always just waited to take a gravity reading after cooling the wort, so I guess I never picked up on it. Below are the readings from the last six beers I've brewed. Notice that pre-boil gravity is much higher than post-boil OG. Not sure if this is normal or not. I just attributed it to the clarifier - less solids after cooling the wort, so a lower gravity.

Thoughts and opinions are apreciated:


Beer..............Pre-Boil.......post-boil
Blond - pils......1.073..........1.062
Blond - 2 row.....1.058..........1.043
Bel Trippel.......1.082..........1.083
Bel Trippel.......1.074..........1.057
Ger Alt...........1.049..........1.046
Surly Cynic.......1.056..........1.046

 

[JDGator]

i'm not really sure how you got those numbers either. it should be the other way around. atleast in all my brews.

What temp are you taking a hydrometer test?

Are you topping up with a bunch of water after you take a reading?

 

[Yooper]

It's not possible that your preboil SG is higher than the post boil SG.

One of two things happened- either the preboil reading wasn't cooled to under 100 degrees before reading and temperature correcting it, or water was added to the post boil reading. There really isn't anything else that could have happened.

One of the readings is incorrect, and I assume it's the preboil OG.

 

[smccarter]

Who knows? It's puzzling to me, that's why I posted here.

 

[duboman]

Who knows? It's puzzling to me, that's why I posted here.

Right, but if you don't provide any answers to the questions or describe your process no one can help you any further.

As stated, what you are experiencing is basically not possible so something is amiss in your readings or how you are making your beer.

 

[vinylrooster]

Who knows? It's puzzling to me, that's why I posted here.

Are you taking your post boil reading after topping up your fermenter?

Maybe it would help if you listed all of your volume readings that you took when you took your SG readings

 

[smccarter]

i'm not really sure how you got those numbers either. it should be the other way around. atleast in all my brews.

What temp are you taking a hydrometer test?

Are you topping up with a bunch of water after you take a reading?

I'm letting the wort cool to as close to 80 as I can, then making the temperature corrections as described.

Not topping up with any water at all.

 

[smccarter]

.. edited

 

[Yooper]

No help necessary from duboman. You've got it man... you are a superior brewer and shouldn't bother with the likes of anyone beneath you. Brew it well my man.

Whoa. Cool it on the attitude.

You posted readings that can not be true. It's obviously an error, and we're trying to help you figure out where it is. It's got to be a measurement error, and we're actually trying to ask you for more information to help you find where. Since YOU are the one asking for help, and you are saying that your readings are accurate, then we are the ones trying to gently convince you that there is no possible way to have the readings you do. In other words, you are making a mistake somewhere.

To cop this attitude with people who are trying to help you will not win you friends.

It's also a very quick way to get uninvited from participating in our forum.

You state that you are "then making the temperature corrections as described", but in no way describing how you are cooling and correcting the preboil readings.

None of us have ESP, but we do know that your readings are incorrect. My guess was preboil readings, but without knowing the cooling method or how you got it to 80 degrees before temperature corrections, it's just a wild ass guess.

 

[smccarter]

Ahh..

Thanks for the help. Brew it well my man. Great forum.

 

[GotPushrods]

Well that was confusing.

 

[duboman]

Whoa. Cool it on the attitude.

You posted readings that can not be true. It's obviously an error, and we're trying to help you figure out where it is. It's got to be a measurement error, and we're actually trying to ask you for more information to help you find where. Since YOU are the one asking for help, and you are saying that your readings are accurate, then we are the ones trying to gently convince you that there is no possible way to have the readings you do. In other words, you are making a mistake somewhere.

To cop this attitude with people who are trying to help you will not win you friends.

It's also a very quick way to get uninvited from participating in our forum.

You state that you are "then making the temperature corrections as described", but in no way describing how you are cooling and correcting the preboil readings.

None of us have ESP, but we do know that your readings are incorrect. My guess was preboil readings, but without knowing the cooling method or how you got it to 80 degrees before temperature corrections, it's just a wild ass guess.

Thank you

 

[jojobrewing]

Ahh..

Thanks for the help. Brew it well my man. Great forum.

on a separate note, i cannot believe you live in Milton, FL. My mom and stepdad moved down there to retire a few years ago and its such a tiny place. small world

 

[ajf]

I would guess that the problem is with your pre boil reading as those gravities look extremely high for pre boil gravities.
After the sparge, your wort in the kettle will be heavily stratified, with the densest (highest gravity) wort at the bottom, and the least dense (lowest gravity) wort at the top.
If you take your pre boil sample from the bottom of the kettle without mixing, it will have a much higher gravity than the average. The solution is to stir the wort well before taking the sample in order to eliminate the stratification problem.
Other possible solutions are:

• Your wort chiller is leaking water, and diluting your beer.
• The humidity in Florida is so high, that you extract more water from the atmosphere than you boiled off while you are cooling.
• You live in an alternate Universe, where the laws of physics don't apply.

-a.

 

[smccarter]

I would guess that the problem is with your pre boil reading as those gravities look extremely high for pre boil gravities.
After the sparge, your wort in the kettle will be heavily stratified, with the densest (highest gravity) wort at the bottom, and the least dense (lowest gravity) wort at the top.
If you take your pre boil sample from the bottom of the kettle without mixing, it will have a much higher gravity than the average. The solution is to stir the wort well before taking the sample in order to eliminate the stratification problem.

That was my thought. I'll use this advise today.. brewing two old ales. I'll stir the wort before taking the sample. That makes sense actually. Good advise, and thanks.

Sorry if I seemed miffed early on in this thread. Bad days lead to bad interpretations of typed messages in a forum.

 

[vinylrooster]

That was my thought. I'll use this advise today.. brewing two old ales. I'll stir the wort before taking the sample. That makes sense actually. Good advise, and thanks.

Sorry if I seemed miffed early on in this thread. Bad days lead to bad interpretations of typed messages in a forum.

Wouldn't hurt to recalibrate your thermometer and write down specific temperatures for each SG reading

 

[smccarter]

That was it. Stirred the wort, pre-boil. Gravity checked out.

Thanks again.

 

[ron,ar]

I also am guilty of not getting true readings too, and like you I usually just take an OG and an FG reading but have started doing the preboil reading just to have more info on each brew record. Some of my inaccurate readings come from taking my gravity reading from a sample from the bottom of the boil kettle. This is because I forget to get a sample from the middle of the kettle beforehand. Then I cool, pitch the yeast and seal, only to find that I don't have a viable sample to measure, so am stuck with the "dregs" in the kettle. Where we get our sample does matter, good clean wort versus bottom of the kettle makes a lot of difference. I suspect the first runnings versus the full sparge volume makes a difference too. It's a learning experience.

 

[smccarter]

I cleaned my refractometer about 2 months ago. Water got inside the device and I wasn't able to read my sample, so being the guy that I am, I disassembled the thing to clean it, so I've been using the hydrometer ever since. That's pretty much the same time I started taking pre-boil readings to calculate efficiency. I'll probably just bite the bullet and buy a new refractometer.

A very interesting hobby, this home brewing.