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Hydrometers and temperature

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Cwrw666

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I always new hydrometers were calibrated for 20c, but didn't realise how much effect temperature as on the reading.
Yesterday I did a brew in the morning and left it no-chilling. Normally I take a hydrometer reading and pitch the yeast just before going to bed but I was going out to a folk music session last night and took a hydrometer reading before going - it was 1043. The brew was still too warm to pitch the yeast so I left it and went out, intending to pitch when I got back. Anyway I forgot and woke up at about 4 this morning and went to do it. The beer was at a nice 20c or thereabouts so I decided to check the hydrometer reading as well as pitch the yeast. This time it was 1052. That's a hell of a difference.
 

terrym

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That's an interesting observation. :hmm:
I too would not have expected such a large difference.
Looked at this which is for water and the difference for SG for water between 4*C and 20* is <1%, and 20*C to 80*C is only 3%.
http://water.usgs.gov/edu/density.html
I would guess this directly compares to wort and consequently to hydrometer readings.
Were the contents of the FV properly mixed at the start, did you you use spray malt at all?
What OG reading were you expecting?
 

Cwrw666

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Who was playing?
It was just a session, in other words anyone who turned up with an instrument. My daughter works in the pub in question and organizes it.
This was from a couple of weeks ago, last night there were loads more of us.

Plash Inn (2)1-11-16.jpg
 

Cwrw666

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That's an interesting observation. :hmm:
I too would not have expected such a large difference.
Looked at this which is for water and the difference for SG for water between 4*C and 20* is <1%, and 20*C to 80*C is only 3%.
http://water.usgs.gov/edu/density.html
I would guess this directly compares to wort and consequently to hydrometer readings.
Were the contents of the FV properly mixed at the start, did you you use spray malt at all?
What OG reading were you expecting?
It was an AG brew so no issues with mixing. I was expecting somewhere around 1050 based on the grain bill and previous brews, so I was a little disappointed when I only got 1043. At a guess I'd say the temperature was about 40c. Glad I took the reading in the middle of the night.
 

terrym

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Ah well. Whatever the reason you got there in the end :thumb:
 

Cwrw666

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Just tested my hydrometer with water at various temperatures:

Fahrenheit centigrade hydrometer

54 ----- 12.2 ----- 1.002
80 ----- 26.6 ----- 1.000
95 ----- 35 ----- 0.998
120 ----- 48.9 ----- 0.994
145 ----- 62.8 ----- 0.990

So I guess the 0.009 difference I had between my wort readings just goes to show my guesstimate of it's temperature was more than a bit out, so the original reading must have been at about 60c.
 

Lord0

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I've noticed too that readings change with temp. Thought it was just me being :drink:
 

Paddyg84

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Simply Google hydrometer temperature correction calculator. You'll get a site that will help. I use this to calculate the sg before I do my boil. This way I know if it's a little weak to boil more vigorously or vice versa.
 
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