How accurate are glass hydrometers

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Kronos

Kronos

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How accurate are glass hydrometers, I have two different ones and when placed in tap water one reads 1.005 and the other one reads 1.007.

What should they read in tap water and is there a preferred make.
 
Clint said:
....what temp is your water? You can find a calibration guide online...
Click to expand...
The water is 25c, I will cool it down to 20c and test again. The only online calibrations guides I can see just say test at 20c and whatever you get + or - just add or subtract this from the actual beer test.
 
Try this...
How to measure Specific Gravity using a Homebrew Hydrometer - The HomeBrew Forum
You might have two different sorts of hydrometer. One measuring at the top of the meniscus, one at the bottom.
Best way to check is dunk them in tap water at 20*C and see what they read.
The Stephenson Reeves brewing/winemaking hydrometer is widely available and in my view is perfectly adequate for the homebrewer.
 
Both state test at 20c on them.

I have now tested at 20c and the ALLA hydrometer now reads 1.004 and the SR hydrometer now reads 1.006
 
Cheap hydrometers have a piece of paper with the scale on. To have 2 that are so far out makes me wonder if you are doing something to dislodge the paper. Do you shake them vigorously to dry them off or something?
 
Ale said:
Cheap hydrometers have a piece of paper with the scale on. To have 2 that are so far out makes me wonder if you are doing something to dislodge the paper. Do you shake them vigorously to dry them off or something?
Click to expand...
I don't shake them and look after them as well as you can.

Can you recommend a non cheap one.
 
Kronos said:
What does that mean?
Click to expand...

The below is how you usually read a hydrometer but on the wilko one the incorrect and correct reading of the below diagram is reversed (so you read the wilko one from the higher point or top of the meniscus,)

index.png
 
Just a thought on this, surely it doesn't matter where you read the hydrometer top or bottom of the meniscus as long as you are consistant?

I just put a few readings into this and adjusted up and down 2 either way & the ABV% was the same.
 
Smileyr8 said:
Just a thought on this, surely it doesn't matter where you read the hydrometer top or bottom of the meniscus as long as you are consistant?

I just put a few readings into this and adjusted up and down 2 either way & the ABV% was the same.
Click to expand...

Your ABV% will remain the same but the residual sugars left in the beer will be different. Now... whether you can taste the difference between a beer that finished at 1.014 to be dryer than a beer that finished at 1.016 is another question!

DA
 
Ale said:
Cheap hydrometers have a piece of paper with the scale on. To have 2 that are so far out makes me wonder if you are doing something to dislodge the paper. Do you shake them vigorously to dry them off or something?
Click to expand...

Also if you wash/clean them in very hot water, it can loosen the glue which holds the paper and let it slide up or down before the glue sets again.
 
DethApostle said:
Your ABV% will remain the same but the residual sugars left in the beer will be different. Now... whether you can taste the difference between a beer that finished at 1.014 to be dryer than a beer that finished at 1.016 is another question!

DA
Click to expand...

Thanks for the explantion, I never really got the whole you need to read from the bottom/top of the meniscus thing, as for residual sugars I doubt my palate is that sophisticated.
 

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