too high an efficiency

[RandalG]

A friend of mine did a partial mash Bender clone the other day from NB. His target og was 1.060. When he was finished he topped with 1.5 gallons and shook vigorously for 2 minutes. He took two separate hydro readings and got 1.090 which I think is physically impossible because of his grain bill. He went to NB the next day because he lives by them and they couldn't figure out how it was so high.He even bought another hydrometer. When he got home he took another measurement with both hydros and they were both at 1.060. I thought somehow he pulled a concentrated sample some how but he shook it first so it should have been mixed well. For the life of me I can't figure out what happened. What do you guys think?

 

[losMythos]

The only thing I can think of is if the readings were done at the same temp. I believe a higher temp causes a false high reading.

 

[prohl84]

If it read 1090 @ 180*F then it would read ~1.121 @ 60*F. High temps cause a low reading since the fluid is expanded low temps cause a false high reading since the wort is more dense.

What was the temperature of the sample? If he had just dumped top off water in it couldn't be that hot.

Sorry I can't help much OP that sure is a head scratcher.

 

[Rkoory]

Actually I believe it works the opposite. High temperatures reduce the density of the wort, reducing the gravity reading. If you read 1.06 at 90 degrees its actually 1.063 at 68 degrees.

That however, does not answer your questions. There are a few peculiarities which can give a off reading, but nothing that I know of that would bias it upward by 30.

My assessment, his hygrometry was upside-down. 060 not 090.

 

[RandalG]

I forgot to mention the sample was at 70 degrees.


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[RandalG]

That's funny that's what I said he read it standing on his head.



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[billl]

This is a very common problem with extract brewing and topping off. Even if you think you are mixing it well, a hydrometer will show you you aren't. It is very, very common to get a non-uniform sample and have the readings be way high or way low.

 

[bleme]

What billl said. When you make a Black and Tan, it separates because the two difference beers are two different densities. That is amplified even more when topping off with water.

On a side note, if he is aerating by shaking, 5 minutes is highly recommended.

 

[prohl84]

Actually I believe it works the opposite. High temperatures reduce the density of the wort, reducing the gravity reading. If you read 1.06 at 90 degrees its actually 1.063 at 68 degrees.

That however, does not answer your questions. There are a few peculiarities which can give a off reading, but nothing that I know of that would bias it upward by 30.

My assessment, his hygrometry was upside-down. 060 not 090.

Yeah that's what I said- density is reduced so the hydrometer sinks deeper= lower number.

EDIT: I used Beersmith hydrometer adjust for my numbers. Agree with stratified wort diagnosis.

 

[losMythos]

Yeah that's what I said- density is reduced so the hydrometer sinks deeper= lower number.

EDIT: I used Beersmith hydrometer adjust for my numbers. Agree with stratified wort diagnosis.

The higher the temp the higher the gravity reading. High temp does not give you a false low reading. Although thats not the issue as it would take a significant temp difference to drop from 1.090 to 1.060.

 

[duboman]

What Bill said,

Because the top off water and the wort were poorly mixed the hydrometer reading was way off. There is still the question of actual efficiency regarding the partial mash part of the equation as depending on how well extraction occurred the readings could still be either high or low but not to the degree stated.

 

[Rkoory]

The higher the temp the higher the gravity reading.

Agree to disagree on this one losMythos.

However, yeah I agree on the reading bias. Too big of a difference to be a temp issue.

 

[RandalG]

This is a very common problem with extract brewing and topping off. Even if you think you are mixing it well, a hydrometer will show you you aren't. It is very, very common to get a non-uniform sample and have the readings be way high or way low.

So what's the best way around this other than doing a full boil? Obviously waiting a day worked but there has to be a better way than that. I guess topping off in the kettle would work if you have room. Being able to stir it would work better than shaking a carboy I would think.

 

[duboman]

So what's the best way around this other than doing a full boil? Obviously waiting a day worked but there has to be a better way than that. I guess topping off in the kettle would work if you have room. Being able to stir it would work better than shaking a carboy I would think.

You also have to remember the recipe is designed as a partial boil so if you alter the method to avoid top off water the recipe needs to be adjusted as well.

If using all extract with maybe some steeping grains the OG reading will ALWAYS be what the recipe states assuming you hit the correct final volume into primary because extract has a fixed gravity contribution.

Partial mash splits this, meaning you need to calculate your efficiency of extraction as the other half of the OG basically....

Assuming you do both these things, regardless of the mix you can assume the recipe's OG is correct, not what you read on the sample


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[billl]

"So what's the best way around this other than doing a full boil?"

Just measure before you top off. The math is really straight forward to figure it out OG by the volumes.