Author Topic: Gravity measuring BS  (Read 1219 times)

Offline yso191

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Gravity measuring BS
« on: August 06, 2015, 10:04:46 PM »
I ranted about this a year ago or so, but I want to get it off my chest again because of a new situation.

I brewed a RIS yesterday and was shocked by a wild miss on the OG.  It should have been 1.092 and it came out at 1.077!  I learned part of that lesson.  I need to decrease the efficiency for bigger beers.  BUT,

I have three gravity measuring devices: a refractometer, and four hydrometers, one of which is a full scale model and three are narrow range models.

I used the high range hydrometer to get the 1.077 OG.  A couple of minutes ago I decided to enlist the others.  The refractometer and the broad range hydrometer were within 1 point of each other...at 1.086!

This makes me crazy.  It's like having an elastic yardstick.  I don't swear very often but this tempts me.
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Offline Pinski

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Re: Gravity measuring BS
« Reply #1 on: August 06, 2015, 10:32:43 PM »
I ranted about this a year ago or so, but I want to get it off my chest again because of a new situation.

I brewed a RIS yesterday and was shocked by a wild miss on the OG.  It should have been 1.092 and it came out at 1.077!  I learned part of that lesson.  I need to decrease the efficiency for bigger beers.  BUT,

I have three gravity measuring devices: a refractometer, and four hydrometers, one of which is a full scale model and three are narrow range models.

I used the high range hydrometer to get the 1.077 OG.  A couple of minutes ago I decided to enlist the others.  The refractometer and the broad range hydrometer were within 1 point of each other...at 1.086!

This makes me crazy.  It's like having an elastic yardstick.  I don't swear very often but this tempts me.

Assuming the temperature has been static on the samples, something is out of calibration.  Did you calibrate the refractometer to zero with distilled water? Do the hydrometers give the same reading in distilled water at the same temperature?
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Offline majorvices

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Re: Gravity measuring BS
« Reply #2 on: August 06, 2015, 11:53:02 PM »
Be sure there is no water in your sample pulling device. If there is some water or sanitizer in there it will throw off your reading. Sometimes a bit of sanitizer gets trapped in the pocket of my zwickle and if I take a sample I have to run out a half pint because the reading will be off. I also recently switched to a digital refractometer that is way more accurate than the old hand held one. Expensive but way worth it!

Offline Stevie

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Gravity measuring BS
« Reply #3 on: August 06, 2015, 11:57:09 PM »
Digital refractometers aren't too expensive compared to the nicer traditional versions. I can't remember which version, but one of the Milwaukee units is often $10-15 cheaper than the normal brix unit, but works just as well.

Edit - I think the normal unit is the 871 which goes to 85 brix. The other is the 884. It has a smaller range, but still within the range needed for brewing and is often cheaper. I've seen it as low as $80 on Amazon.
« Last Edit: August 07, 2015, 12:00:17 AM by Steve in TX »

Offline hopfenundmalz

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Re: Gravity measuring BS
« Reply #4 on: August 07, 2015, 11:56:03 AM »
Check all for zero with water. Then if you have time, you can mix a 10P solution of water and sugar, and see which ones read closest to 1.040.

You have different devices that need to be calibrated. If you have 2 clocks, or two thermometers, do you expect them to be the same?  ;D
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Offline David Lester

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Re: Gravity measuring BS
« Reply #5 on: August 07, 2015, 06:36:37 PM »
I remember your last rant.

This is a good subject to remind us to calibrate. From what I remember Hydrometers can be off and final readings have to be adjusted to the calibration. Would you agree that the little piece of paper in the hydro can move around? I ask because I'm not sure

DL

Offline David Lester

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Re: Gravity measuring BS
« Reply #6 on: August 07, 2015, 06:38:28 PM »
Check all for zero with water. Then if you have time, you can mix a 10P solution of water and sugar, and see which ones read closest to 1.040.

You have different devices that need to be calibrated. If you have 2 clocks, or two thermometers, do you expect them to be the same?  ;D

+1 good idea

Offline Pinski

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Re: Gravity measuring BS
« Reply #7 on: August 07, 2015, 07:09:43 PM »
Would you agree that the little piece of paper in the hydro can move around? I ask because I'm not sure

It's certainly possible.
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Offline HoosierBrew

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Re: Gravity measuring BS
« Reply #8 on: August 07, 2015, 07:19:11 PM »
Would you agree that the little piece of paper in the hydro can move around? I ask because I'm not sure

It's certainly possible.

+2. It can and will. One of my hydros reads .002 high because the paper noticeably shifted. I check every time now.
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Re: Gravity measuring BS
« Reply #9 on: August 07, 2015, 08:35:42 PM »
I used the high range hydrometer to get the 1.077 OG.  A couple of minutes ago I decided to enlist the others.  The refractometer and the broad range hydrometer were within 1 point of each other...at 1.086!

So it's probable, but by no means certain, that your high-range hydrometer is out of whack. I'd calibrate all three with a ~1.080 sucrose solution.
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Offline pete b

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Re: Gravity measuring BS
« Reply #10 on: August 09, 2015, 12:08:44 PM »
It seems to me there would be a market among home brewers for higher quality hydrometers. I certainly would be happy paying $50+ for one that stayed calibrated for years instead of &15 for a crappy one with paper that slips. Are they out there? The paper slipping problem seems kind of inexcusable, that seems easy to fix yet its very common.
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Offline a10t2

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Re: Gravity measuring BS
« Reply #11 on: August 09, 2015, 03:09:08 PM »
Hydrometers are about as cheap as labware gets. That said, your LHBS should be able to order these: https://bsgcraftbrewing.com/plato-saccharometers0-85-9364 The set of three runs about $120.
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Offline pete b

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Re: Gravity measuring BS
« Reply #12 on: August 10, 2015, 11:33:37 AM »
Hydrometers are about as cheap as labware gets. That said, your LHBS should be able to order these: https://bsgcraftbrewing.com/plato-saccharometers0-85-9364 The set of three runs about $120.
Do you have these and if so have they stayed calibrated longer than the cheaper ones.
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Offline Scot (one T)

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Re: Gravity measuring BS
« Reply #13 on: August 10, 2015, 01:50:55 PM »
The way they are handled factors in how long they stay calibrated.  The paper is not glued in place and will move when bumped.  If you drop them into the sample jar and they bounce off of the bottom, the paper will likely move. 
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Offline Stevie

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Re: Gravity measuring BS
« Reply #14 on: August 10, 2015, 02:03:59 PM »

The way they are handled factors in how long they stay calibrated.  The paper is not glued in place and will move when bumped.  If you drop them into the sample jar and they bounce off of the bottom, the paper will likely move.
My current hydrometer appears to have a dab of glue or wax holding the paper at the beginning of the stem.