Hydrometer vs Refractometer

Discussion in 'General Home Brew Equipment Discussion' started by MonkeyMick, Oct 15, 2019.

Help Support The Homebrew Forum UK by donating:

  1. Oct 15, 2019 #1

    MonkeyMick

    MonkeyMick

    MonkeyMick

    Active Member

    Joined:
    Jun 10, 2019
    Messages:
    93
    Likes Received:
    16
    Hey..

    Ive just aquired a refractometer and calibrated it using distilled water. When I've checked my lager and pale ales that should be ready, both are showing SG of over 1.020. Checking with my hydrometer shows them at 1.008 and 1.012 respectively.

    Ive checked the hydrometer in room temp tap water, and it was reading 1.000.

    Is it safe to assume the refractometer is goosed, or can they be repaired at all?

    Thanks!
     
  2. Oct 15, 2019 #2

    Horners

    Horners

    Horners

    Landlord. Supporting Member

    Joined:
    Jan 9, 2018
    Messages:
    503
    Likes Received:
    187
    Location:
    NULL
    Refractometer only really useful for measuring gravity of wort pre fermentation. The alcohol in solution throws it out. You can record samples over a number of brews and derive a wort correction factor but IMHO better sticking with hydrometer once fermentation underway.
     
    MonkeyMick likes this.
  3. Oct 15, 2019 #3

    MonkeyMick

    MonkeyMick

    MonkeyMick

    Active Member

    Joined:
    Jun 10, 2019
    Messages:
    93
    Likes Received:
    16
    Thanks! I also think I've gone wrong with using warm water to calibrate then measuring samples straight from the fridge..
     
  4. Oct 15, 2019 #4

    Horners

    Horners

    Horners

    Landlord. Supporting Member

    Joined:
    Jan 9, 2018
    Messages:
    503
    Likes Received:
    187
    Location:
    NULL
    The good thing about refractometer is that you only need a drop so even if use warm wort it adjusts to ambient temperature very quickly. I use mine to get a gravity reading post boil and then work out any necessary dilution to get down to required OG.
     
    MonkeyMick likes this.
  5. Oct 15, 2019 #5

    Davvy

    Davvy

    Davvy

    Active Member

    Joined:
    Mar 6, 2019
    Messages:
    47
    Likes Received:
    14
    When I started all grain brewing I bought a cheap one from Fleabay, and wanted it for post fermentation duties - but realised pretty quickly that the result was nothing like the hydrometer....
    It now lives in the cupboard where all my irrational and useless purchases from the internet reside....!!!
     
    MonkeyMick likes this.
  6. Oct 15, 2019 #6

    Norfolk79

    Norfolk79

    Norfolk79

    Landlord. Supporting Member

    Joined:
    Oct 7, 2016
    Messages:
    711
    Likes Received:
    251
    Location:
    Norwich
    You have to adjust for the alcohol in the sample, which as been said throws the readings out.

    Brewers Friend have a calculator on their website which does this athumb..
     
    Last edited: Oct 16, 2019
    MonkeyMick and Drunkula like this.
  7. Oct 15, 2019 #7

    Brewed_Force

    Brewed_Force

    Brewed_Force

    Member

    Joined:
    Sep 24, 2014
    Messages:
    424
    Likes Received:
    120
    Location:
    Liverpool, UK
    MonkeyMick likes this.
  8. Oct 15, 2019 #8

    Drunkula

    Drunkula

    Drunkula

    Landlord.

    Joined:
    Dec 1, 2017
    Messages:
    1,310
    Likes Received:
    790
    I absolutely love my refractometer. Because for large batches I have to make a thicker wort and water it down I can get an idea of efficiency an what gravity to expect as soon as I start the boil. You've got to learn how to use a refractometer like tilting the screen slightly upwards and lowering the screen slowly so all the bubbles are pushed to the top. You end up with a much sharper line between the light and dark doing that.

    My final gravity is always one point off a hydrometer reading using 1.0 as the correction factor when it's fermenting/ed.

    It cost £4.43 from Ebay. It says it's ATC, which means it's supposed to adjust for wort temperature but that's crap, and I think most of the ones under 20 quid are exactly the same. It'll shift a tiny bit as it cools. But don't let it cool with the windon open as water will evaporate leaving you with a higher measurement. So don't let very small samples cool on a spoon for the same reason.
     
    MonkeyMick likes this.
  9. Oct 16, 2019 #9

    private4587

    private4587

    private4587

    Member

    Joined:
    Sep 11, 2016
    Messages:
    348
    Likes Received:
    38
    Location:
    Middlesbrough
    I use my refractometer all the time after checking against my hydrometer and finding that results are the same after using refractometer correction factor. the program i use is an excel one can not remember the author i have attached the file.
     

    Attached Files:

    MonkeyMick likes this.
  10. Oct 16, 2019 #10

    woody1959

    woody1959

    woody1959

    Active Member Supporting Member

    Joined:
    Sep 10, 2019
    Messages:
    58
    Likes Received:
    18
    Location:
    London UK
    I have one of these cheapy ATC ones purchased from ebay and I use it all the time, BUT only to check if my brew is ready, if it shows that the gravity hasn't moved for 3 days then fermenting is done.
    Saves taking out 100ml each time for a trial jar and hydrometer test.

    I will use the hydrometer to confirm ABV but because I have the refractometer it now only gets used twice, once before I pitch the yeast and once before I keg.
     
    MonkeyMick and Sadfield like this.

Share This Page