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Hydrometer Corrections

I’ve been experiencing and lamenting beer that seemed to finish with a higher specific gravity than I wanted or anticipated. On my most recent batch of Hefe, I got the same result. This seemed really weird because like most of my beers that I have had this issue with, it didn’t taste like a higher finishing SG beer. Who knows why the light goes off when it does, but it did and I found the culprit to my problem.

We have talked about calibrating equipment before. And to be technical and anal about it… you can calibrate an hydrometer. Calibration implies the ability to reset an instrument to a set point. Whereas every reading made there after is correct. You can’t change the calibration on a hydrometer with any true precision. (Now don’t get me start on people you either add or remove weight to a hydrometer by either painting nail polish on it or lightly sanding away some of the glass. Highly difficult to dial in and be reliable.)

Nope with a hydrometer all you can do is devise a correction factor. A correction factor is a constant, or an equation or some sort of algorithm that you apply to the measurement after the test if completed by the otherwise offendingly off kilter measurement tool. In this case we are still talking hydrometers. To set an correction factor you would need to make a series of solutions of known concentration make the measurements and record in that range what the correction needs to be. Its not hard but you need to be able to make accurate test solutions of known value. In case you are wondering specific gravity is in grams/millileter.

End my diatribe about calibration and corrections.
There is another way! Wait for it…. Buy a new hydrometer!
So when I was getting perplexed I remembered that I had bought a back up hydrometer years ago. I dug it out, still wrapped in bubble wrap from shipping. Dropped it in the beer sample.. BOOM!!! sure enough I was on target with what I thought was more reasonable for the beer.

The moral of the story is to be sure you know what your tools are telling you. I had been scratching my head each brew wondering about ingredients, mash temps and process issues. Trying to solve the SG issues. Only to realize that my hydrometer was failing me. A quick replacement and I was back in business.

BREW ON! Hopefully more accurately.

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2 Comments

  1. Question: if I put my hydrometer in a known solution, for example water, and it reads 1.001 (.001 above what’s to be expected), will each subsequent wort reading be .001 above the ‘true’ reading, or might this offset change depending on the SG of the wort being tested. In other words, does the ‘offset correction value’ remain the same across the board, or might it increase in a linear fashion?

  2. This is too funny. I have been having a very similar problem with my beers for about the last 3 months. My FG would keep dropping , on beers that I knew no way had any sugars left to ferment. The last beers that I did were a blue moon clone using WLP320, and S-05 to Make a strawberry wheat. I split a 10 gallon batch in half to have 2 really different beers. The Lowest I was looking for was 1.012, but it kept falling and they both finished at 1.008. I even left them both in the Fermenters for a month just to make sure they would not drop any more.
    So, thanks for the suggestion, a new Hydrometer it is. I’ve had it for 5 years now, I guess it’s time for a new one.

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