Hydrometer readings at differant temperatures

[Matty A]

Hi Guys,

 

Just from reading the forums i have noticed that depending on the temperature will determine whether the hydrometer reading would be a little incorrect.

 

Is there a formula or a general rule to go by to determine how out the hydrometer is.

 

I am mainly thinking that if I test it on a cold day it will say that it is a specific OG. Then I test in on a warmer day and it says the same reading where as it is still fermenting and the slight error is coming into play.

 

I come from a wierd location near Orange and Bathurst where it was snowing a couple of weeks ago and now it is close to 25 degrees.

 

Just let me know if I am trying to make this more scientific than it needs to be as well [biggrin]

[Matty A]

Although when I say the temparature varies so much. The fermanter temperature has varied from around 16 degrees to 22 degrees

[Kearnage]

There are a number of online calculators. Most seem to be in that weird fahrenheit thing, and adjusted to 60 F (15 deg C) but the Coopers kit hydrometer is calibrated to 20 C.

Here is a calculator someone else on the list linked to a while back:

Hydrometer temp correction

 

So check what your hydrometer is calibrated to (ie the temp in water where you get a reading of 1000), it should be on it or with the instructions, then put in your sg reading, temperature it was taken at, check 'celsius' and put in the calibration temp (eg 20 deg) in the bottom box, and hit 'calculate'

It's easier than I made it sound!

 

 

[Matty A]

I was just having a play with the calculator and even 8 degrees doesnt make that much of a differance to the reading.

 

Do you guys think it is necessary to worry this much about doing this sort of thing. My last brew I wasn't overly worried as it was in plastic although I have left this brew alot longer knowing that it will be my first glass brew.

 

I think the key would be to just leave it in the fermenter until I am 100% sure it is ready to bottle.

 

Thanks,

 

Matt

[PB2]

15C subtract .001

20C

25C add .001