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So I've brewed between 6-10 batches of beer at home using partial boil methods but have never managed to get accurate gravity readings.

The issue I have is that my readings somehow always seem to be way higher than most gravity-abv charts ive seen allow for, even when i try and account for temperature.

For example, today I brewed something akin to a DIPA which used 9 lbs of liquid malt (6 pilsner, 3 amber) in a 5 gallon batch. After adding a hops, chilling and adding water to get to the desired 5 gallons, I extracted some and got an OG reading of 1.12 which puts me in the running for maybe a 15% abv beer, which seems hard for me to believe.

Is this a reasonable number considering how much malt I used? Something I have noticed is that in my OG readings theres always a very large amount of sediment since I usually extract the liquid soon after everything is in my fermentation chamber. Could this sediment be affecting my readings?

as a small aside, i've been trying to use a wine thief to get readings and it always seems to get clogged due to high amounts of sediment in the fermentor. Is there a way around this aside from getting something akin to a turkey baster?

Thanks for the help!

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Have you tried using another hydrometer? Is it possible it's badly calibrated and floats high? –  Mere Development Mar 16 '13 at 23:29
    
Possible duplicate of homebrew.stackexchange.com/questions/1650/… –  MalFet Mar 17 '13 at 0:24
    
@MereDevelopment, yes this is the second one ive had issues with, last one i cracked by mistake. and malFet, thanks for the link ill check it out –  MSEoris Mar 17 '13 at 0:31
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2 Answers 2

Here's some tips on getting an accurate hydrometer reading:

  • check the hydrometer is calibrated, by checking that water reads 1.000 at the calibration temperature (either typically 65F or 20C). I've tried both distilled water and tap water and by both read the same.

  • when taking a sample from a extract-based brew, particularly partial boil where top up water has been added, ensure the wort is mixed thoroughly, or the wort will be stratified with high density extract at the bottom and lower density water towards the top.

  • take the gravity sample from the middle to top of the fermentor. This helps avoid taking up any sediment.

  • if any sediment does make it into the sample, wait for it to settle out before taking a reading

  • wait for the sample to reach calibration temperature. Although charts can be used to correct for different temperatures, they are only approximate - SG change over temperature depends upon the specific content of the wort.

  • when taking the reading, ensure that the hydrometer does not touch the sides of the test cylinder, and read with eye level at the liquid level.

  • it's also a good idea to spin the hydrometer to release any tiny air bubbles that may be trapped underneath

In your case, it does sound like a mixing problem. 9lbs of extract in 5 gallons should come out at 1.065. Assuming you've checked your hydrometer for accuracy, then I think it's to do with mixing. It's best to put the lid on, and shake the carboy to get oxygen into the beer. This will also homogenize the wort so that there are no high or low density parts, and your gravity sample will be more truthful.

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All this is great advice, but the only thing I know that could account for a reading that's double the expected OG is inadequate mixing after the top up water is added. Sediment, miscalibration, innaccuracy of temp/gravity charts -- these could give a few points deviation for a true reading, but not 60 points. –  Tobias Patton Mar 17 '13 at 15:36
    
Very true, Tobias. –  Denny Conn Mar 17 '13 at 17:55
    
Did you see my last paragraph? I do say is a problem with mixing the wort. The other points above are to answer the actual question asked - how to ensure an accurate hydrometer reading. –  mdma Mar 17 '13 at 18:05
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An OG reading of 1.12 seems about double what you would expect for that grain bill, and gravity is only really affected by dissolved solids. Obviously the first thing you should do is check your hydrometer to make sure it is accurate, that is almost certainly the cause of the error.

In water the specific gravity should read 1.00 since specific gravity is just the relative density of some substance compared to the density of water. If your hydrometer is significantly different from 1.00 it is probably poorly calibrated. Another easy one to check is milk, it should have a specific gravity of around 1.035 (but obviously this can vary greatly, it is only a rough estimate).

If you want another accurate reference point, you can mix, by weight, 10% sugar with 90% water and you should get a specific gravity of 1.04 (e.g. 10 grams of sugar with 90 grams of water).

As for the thief issue, you should be able to steal some wort without stirring up too much sediment. Due to it's design, you don't need to touch the bottom with it to get it to fill, so as long as you are careful while opening the bucket and don't stir the bottom you shouldn't get too much sediment. One trick if the thief isn't immediately filling is to shake it up and down a little while submerged and that should get the stopper to open.

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a lot of useful into there. one correction - it's 10 parts sugar to 100 parts water, not 90. 1.040 is about 10 brix, which by definition is 10% sugar solution - 10 parts sugar to 100 parts water. see en.wikipedia.org/wiki/Brix –  mdma Mar 17 '13 at 1:22
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"One degree Brix is 1 gram of sucrose in 100 grams of solution". Doesn't that mean 1 gram of sugar and 99 grams of water to make 100 grams of solution? –  Tobias Patton Mar 17 '13 at 15:33
    
ah, my bad. You're totally correct, it just sounded wrong when I read it. To be sure, I did a test - dissolved 10g sugar in 40g water - the refractometer shows 20 brix (and not 25.) It seems strangely non-linear that the water decreases and the sugar increases, but that's how the scale is defined. –  mdma Mar 17 '13 at 16:45
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