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Preboil gravity VS Original gravity

 
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biglakewill




Joined: 30 Dec 2012
Posts: 69
Location: NC

Drinking: Barley Wine

Working on: Weissbeir


PostLink    Posted: Mon May 19, 2014 6:50 pm    Post subject: Preboil gravity VS Original gravity Reply with quote


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Looking for some thoughts and/or ideas:

I have brewed 5 batches to date on my system. 2 electric pale ale, a Janet's brown ale, a wheat and Hop Slam Clone, all of which have come out GREAT and had great reviews from friends.

My problem, which makes no sense, is that on each batch my preboil gravity is significantly higher than my original gravity after the boil.

I take my preboil sample from the bottom valve after I have collected my boil volume. Filling my BK is done through my whirlpool fitting so I assume it is well blended. I take the original gravity after the boil and the wort has been transferred to the fermenter, before added the yeast.

My last batch, electric pale ale, the preboil was 1.065 (which I can't believe). The OG was 1.048 a bit low, but believable. I use a hydrometer and let the wort cool to close to 60 F before reading.

Any thoughts???

Thanks

Bill
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huaco




Joined: 05 Apr 2012
Posts: 1506
Location: Burleson Texas


PostLink    Posted: Mon May 19, 2014 7:09 pm    Post subject: Reply with quote

Sounds like maybe the valve has some first running still in it. Try to run a pint of wort out of the valve first (returning it back to the top of the kettle), then take a sample from it.
Also, If you fill the kettle through the whirlpool and are sparging slow like is outlined in Kal's brew day instructions, the whirlpool won't have enough velocity to actually get things stirred up very well. Give it all a good stir with a spoon...
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biglakewill




Joined: 30 Dec 2012
Posts: 69
Location: NC

Drinking: Barley Wine

Working on: Weissbeir


PostLink    Posted: Mon May 19, 2014 8:34 pm    Post subject: Reply with quote

Huaco

Good points. I will give it a try. Didn't give much thought to the velocity. But you are right, at the slow sparging rate it would not be enough to blend the wort up.

Thanks for the ideas... I will let you know how the next brew goes.
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Holter




Joined: 07 Oct 2011
Posts: 221
Location: Los Angeles, Ca


PostLink    Posted: Tue May 20, 2014 1:39 am    Post subject: Reply with quote

I am never able to get an accurate pre boil gravity until the wort is near boiling which mixes up the liquid well. I use a refractometer.
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Holter
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kal
Forum Administrator



Joined: 12 Dec 2010
Posts: 11116
Location: Ottawa, Canada

Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter


PostLink    Posted: Tue May 20, 2014 12:10 pm    Post subject: Reply with quote

+1. You need to stir well before taking a pre-boil gravity reading. I usually just float my hydrometer in the kettle, and if I don't stir it first, it'll be too low.

Kal

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huaco




Joined: 05 Apr 2012
Posts: 1506
Location: Burleson Texas


PostLink    Posted: Tue May 20, 2014 12:19 pm    Post subject: Reply with quote

Kal, do you just perform a temp correctionnon the hydrometer floating in that hot wort?
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kal
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Joined: 12 Dec 2010
Posts: 11116
Location: Ottawa, Canada

Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter


PostLink    Posted: Tue May 20, 2014 12:30 pm    Post subject: Reply with quote

Yup. Really simple to do in software. I just float and measure, simpler than taking a sample/cooling. You can see it floating on the right in this picture:



Then in Beer Tools Pro I enter the SG reading, wort temperature (68F in the screenshot below, but would be more like 140-150F in this case), and hydrometer calibration temperature (60F for my hydrometer):



Only caveat as mentioned above is that you have to stir first to make sure to get the thicker wort off the bottom. I use my mash paddle and gently go back and forth for a few seconds. It doesn't take much.

See here for hydrometer details: http://theelectricbrewery.com/parts-list-using?page=7

Kal

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We ship worldwide and support our products and customers for life.
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Last edited by kal on Tue May 20, 2014 1:12 pm; edited 2 times in total
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biglakewill




Joined: 30 Dec 2012
Posts: 69
Location: NC

Drinking: Barley Wine

Working on: Weissbeir


PostLink    Posted: Tue May 20, 2014 1:00 pm    Post subject: Reply with quote

Thanks all, appreciate the thoughts and ideas.

And Kal....thanks again for the great system! I have a few beer fanatics as friends. The beers I have made to date with your system and recipes have all gotten rave reviews.
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mnoltimier




Joined: 10 Oct 2011
Posts: 60
Location: Berthoud, CO

Drinking: Big Nut Brown Ale, Sky Pond Pale Ale, Smashin' Punkin, Berlinner Weisse, Vienna Lager, Hopulence IIPA, Helles Angels

Working on: Maude Flanders Red, Gallagher's Watermelon Wheat


PostLink    Posted: Thu Aug 21, 2014 6:30 pm    Post subject: Reply with quote

The preboil gravity will never be higher than the post boil gravity. You are boiling out water making your wort more concentrated thus making the post boil gravity higher. The only way your post boil gravity (OG) will be higher than the preboil gravity is if you add water when you are done boiling. I have learned that refractometers can be all over the place due to their small sample size. Hydrometers are way more consistent. It is a process problem.
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