Refractometer

[daddies-beer-factory]

Hi, I got one of the refractometers from amazon this xmas as discussed on JBK (before xmas) & I am getting strange readings.

I calibrated it this morning to zero, off some distilled water off the inside of the kettle lid.

Refractomer - Hydrometer

1081 - 1070 1st Runnings
1032 - 1032 after 1st Sparge
1017 - 1017 after 2nd Sparge
1047 - 1044 Original Gravity
(refractometer reading 1st, then hydrometer reading)

I understand that the readings can alter once alcohol is present also but I thought the above readings would be more accurate ?
hydrometer readings were cooled to 18 C

Any help on understanding this would be appreciated ?

[oz11]

Take several readings with the refractometer, discard the lowest and highest, then take the average of the others.

See also here

[Jim]

Despite all the caveats re using the SG gravity scale on these things I've found mine tallies pretty well with my hydrometer.

Personally, I expect an approximate indication of SG rather than expecting it to be a precision measurement whatever method I use to measure it - why would you want any more in a HB situation? The cost of true precision in any measurement can be very high!

[BenB]

Did you take the hydrometer sample from the trial jar? Did you shake the trial jar before taking the refractometer sample? One thing I've found with hydrometers is that the small sample required (the whole advantage of using a hydrometer) makes them vulnerable to heterogeneity within the sample. When I've just taken a quick pipette from the top of the boiler after various runnings my samples have made no sense- needs a quick stir to make the sample more representative of the wort as a whole. This is exacerbated by the fact by definition the higher density runnings will tend to be first into the boiler and will tend to remain there with the "lighter" runnings just sat on top. At least until the boil- you would hope that would make things more homegenous.

Also- you mention the refractometer readings were done at 18 degrees- what about the hydrometer readings? Have you tested the calibration of the hydrometer? Compensation tables are no use if the hydrometer is off wack.

Very interesting though!

[Martin G]

Agree with the point about stirring, it takes more stirring than you'd think to get the liquids at different temperatures and with differing sugar concentrations to mix.

[daddies-beer-factory]

I kept the runnings from the brewday, and the next day with this advice took 5 readings from every sample and discarded the highest and lowest.

The samples were collected through the tap in the bottom of the mash tun/ boiler on brew day - Ben as you say the dense liquid is in the bottom.

The samples had 24 hrs at room temp , and 5 refractometer readings were taken and 1 hydrometer.

In conclusion I was much happier with the 2nd set of results being much closer to the hydrometer.

(the hydrometer is calibrated)