| Author |
Message |
    
Mike Huss
Intermediate Member
Username: Mikhu
Post Number: 399
Registered: 03-2003
| | Posted on Friday, January 21, 2005 - 07:33 pm: | 
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So I figured out that my stupid hydrometer is bad. The good news is my efficiency isn't as bad as I thought and I can stop wondering why my FG's are coming out so low.
When I checked it in 60 deg distilled water it gave me a .992 reading. Question is, is that error off in a linear fashion vs temp? In other words, can I assume for my last batch where my FG was 1.004, is that really 1.012? And as for temp, what about my OG after the mash? Do I just add those 8 points no matter the temp?
I'm really just wondering what the true numbers were for this last batch so I can get a better idea on my efficiency. I plan on replacing that piece-o-crap before I brew again. |
Bill Pierce
Moderator
Username: Billpierce
Post Number: 1936
Registered: 01-2002
| | Posted on Friday, January 21, 2005 - 07:38 pm: |
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There was an article in Zymurgy a few years back about making reference sugar solutions for hydrometer calibration. I'll see if I can find the issue. |
Rob Farrell
Member
Username: Robf
Post Number: 232
Registered: 02-2003
| | Posted on Saturday, January 22, 2005 - 02:17 am: |
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The error is linear. If your hydometer is calibrated at 60 F, then just add 0.008 to your readings. Apply temperature correction (which is not linear) to the corrected reading. |
Mike Huss
Intermediate Member
Username: Mikhu
Post Number: 402
Registered: 03-2003
| | Posted on Saturday, January 22, 2005 - 03:24 am: |
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Thanks guys! |
Richard Nye
Advanced Member
Username: Yeasty_boy
Post Number: 509
Registered: 01-2004
| | Posted on Saturday, January 22, 2005 - 11:34 am: |
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Mike and Rob, not so fast. I have (had) a hydrometer that was off by 5% over the whole range! In fact, it read 0 when I put in 6oF water. But at 1.050 it read 1.055. The only way I can explain it is the paper inside the hydrometer (with the scale on it) may have been reduced during a photocopying process. I just bought 3 narrow range hydrometers then a refractometer. Those more accurate instruments cleared up a lot of questions I had about my brewing. |
Richard Nye
Advanced Member
Username: Yeasty_boy
Post Number: 510
Registered: 01-2004
| | Posted on Saturday, January 22, 2005 - 12:26 pm: |
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Oh, the other half of that post is I discovered this by making some sucrose solutions that Bill mentioned. A 10 degree Plato solution (1.040 S.G.) is 10% sucrose by weight and 90% water. Mix up the solution (making sure all of the sugar dissolves), measure this with your hydrometer and see what you get (after temperature corrections).
20 degree Plato = 1.083 = 20% sucrose by weight
Here's a good article to read from Brewing Techniques:
http://www.brewingtechniques.com/library/backissues/issue1.3/manning.html |
Bill Pierce
Moderator
Username: Billpierce
Post Number: 1947
Registered: 01-2002
| | Posted on Saturday, January 22, 2005 - 02:04 pm: |
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Thanks, Richard. When preparing solutions for hydrometer calibration, measure the sugar very accurately by weight, within 1 gram. And if possible measure the water volume to the nearest milliliter. |
Rob Farrell
Member
Username: Robf
Post Number: 233
Registered: 02-2003
| | Posted on Saturday, January 22, 2005 - 03:50 pm: |
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I had assumed the paper had slipped or the weight was off. I should have stated that. You know what they say about assuming. |
Richard Nye
Advanced Member
Username: Yeasty_boy
Post Number: 514
Registered: 01-2004
| | Posted on Saturday, January 22, 2005 - 06:03 pm: |
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Rob, that's probably what happened, but maybe not. Better to check. |
Brews and Views Archive 2005 
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