getting accurate gravity readings during sparge

This may be just a noob question, but here it goes:

I was told that gravity readings are not very accurate if the runnings are very hot.
I was brewing last night, watching the gravity readings to ensure that I didn't go below the 1.008 - 1.012 reading but I know it couldn't have been completely accurate since the runnings were around 170F. I let it sit for a little to cool down but it didn't cool too much, too quickly.

What temperature does it need to be in the hydrometer test jar to ensure an accurate reading....
What do you guys do to make sure you get an accurate gravity reading?

Thanks in advance...

Most hydrometers are calibrated to 60F, check the documentation that came with yours.

To get it to that level quickly you'd have to get the sample into an ice bath and even that won't be very fast. I know I've seen calculators online for adjusting hydrometer readings based on high temperature but I haven't used them to be able to speak to how accurate they are.

I use an ice bath to lower the temperature of the sample. I only check it when I reach the preboil volume. I like to get the temp around the 100 degree range.

Here's a link to a simple chart of adjustments: http://www.ebrew.com/primarynews/ct_hydrometer_temp_correction.htm

I don't bother calculating the adjustments during sparging, I mostly just keep tabs on how fast the gravity is falling off during the sparging process.

BakerStreeBeers said:

Here's a link to a simple chart of adjustments: http://www.ebrew.com/primarynews/ct_hydrometer_temp_correction.htm

I don't bother calculating the adjustments during sparging, I mostly just keep tabs on how fast the gravity is falling off during the sparging process.

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Thanks for the link, that is very helpful!

what happens if you fall below the 1.008 mark?

boothbrew said:

This may be just a noob question, but here it goes:

I was told that gravity readings are not very accurate if the runnings are very hot.

Click to expand...

It's a non linear correction, so when your wort is hot your ability to accurately read the hydrometer at the same time getting the correct temperature is going to be the determining factor in getting the correction to be accurate. What I mean by this is that if you are off a degree or point in either measurement at say 180 °F it will yield a much bigger difference than when you are at room temp. I think the charts/calculators are correct/work properly, but I noticed early on that my readings were off when taken with hot wort. You have to 1) be very precise in your measurement and 2) take it with a 'grain of salt' as they say.

what happens if you fall below the 1.008 mark?

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You boil a little longer.

I just used a refractometer for the first time last weekend (my dad bought one for his wine making ) and it was AWESOME! I really liked being able to check my gravities throughout the brewday and have confidence in the sparge gravities. I did double check my readings with the hydrometer just to be sure.

The refractometer only uses one or two drops of wort so it equalizes temperature in a second and gives an accurate reading. It took about 12 minutes to get my hydrometer test jar down to 60 degF to verify the readings and they were spot on. I think I will be able to "borrow" this refractometer quite often .

I highly recommend getting one of these as it really did make taking measurement more fun and SUPER easy. I will definately still use my hydrometers for measuring my OG.

I am going to test the conversion calculators to account for alcohol next week and I will post something about how close it comes. It is just so much quicker and takes almost no volume to do a refracto reading.

Just my .02 Cheers

david_42 said:

You boil a little longer.

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why is that?

below 1.008 you will be extracting tannins and other astringent flavors into your beer. Needless to say this is not desirable. The longer you boil the more evaporation you have and your wort becomes more concentrated. If your gravity is low, you can boil longer to reach your target OG.

I generally take an aluminum sauce pan and keep it in the freezer to get the metal cold.

I fill a small amount of runnings in the sauce pan and put it back in the freezer for a few minutes. This drops the temp very quickly to take a sample reading.