Hydrometer Correction

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Gavagai

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I tested my hydrometer in distilled water at ~65F (hydrometer is calibrated at 68F). It read 1.003, so I've been adjusting my hydrometer readings accordingly. But the corrected readings just don't seem right. I've got an all malt pale ale (single infusion @ 152) fermented with US05 that's reading 1.010. After correction that would be 1.007, but it really doesn't taste that dry, and I certainly wasn't expecting that level of attenuation.

What do you think? Is my hydrometer inaccurate as well as mis-calibrated? It is a cheap model.
 

Kaiser

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check your hydrometer with a 20 Plato/Balling/Brix solution. You can make it by mixing 40g table sugar with 160g water. Then dilute that solution by taking 100g of it and mixing it with 100g water (go by weight). the result is a 10 Plato/Bailling,Brix solution. You can keep going with this and make 5 and 2.5 Plato solutions. Check your hydrometer with that.
 
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Gavagai

Gavagai

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How much attenuation is that IOW what was the OE?
OG was 1.052 (1.055 without correction). So 1.007 would be 86% apparent attenuation.

I will check my hydrometer as you suggest, Kai. Thanks for your help.
 
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Gavagai

Gavagai

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Huh. The hydrometer seems to consistently read 0.5˚ Plato high. I guess the pale ale really is under 1.010.
 

ajdelange

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That is very high attenuation for sure.

I think you can assume there is a 3/4 °P bias. The paper can slip in the tube (and you can try tapping the hydrometer at the appropriate end to move it back to where it should be with as much vigor as you feel comfortable with understanding that you may break it) but it won't stretch so a slope error can't occur (there will, in fact, be a small slope error as the scale isn't quite linear).

Attenutation that high is suggestive of contamination with some hyper attenuative yeast strain or bacterium. It tastes OK though?
 
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Gavagai

Gavagai

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The beer is very good. No off-flavors that I can taste, and there's a lot of malt flavor from the 20% Munich in it. Nor is it overly thin. It's also only been fermenting for a week, and my experience with hyperattenuation due to infection has been that it takes a bit longer. It is possible, though. Fingers crossed.

The other explanation is that my mash tun loses a lot of heat (true, I think the mash dropped to 146 or so by the end), and during my 90 minute mash I just ended up with a very fermentable wort.
 

Kaiser

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but it won't stretch so a slope error can't occur (there will, in fact, be a small slope error as the scale isn't quite linear).
That's what I wanted him to check. Maybe cheap hydrometers can have a manufacturing flaw where the diameter of the tube is not to spec.

Kai
 
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Gavagai

Gavagai

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Not this one, apparently. I checked it at 10K and 2.5˚ and it was 0.5-0.75˚ high for both.
 

WoodlandBrew

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Perhaps the water used to calibrate the hydrometer wasn't clean? Or perhaps the temperature of the water used to calibrate wasn't the same as the beer that was measured? Kai's method of testing is a good way to check it. AJ's right that there could be a few points of variance from stratification. Can you check the beer with a refractometer as well. With a final hydrometer and refractometer measurement the ABV and OG can be estimated. That might give you some confidence on your OG reading.
 

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