Sticky Fingers

[orlando]

My brand spanking new Refractometer arrived yesterday accompanied by instructions in Engrish and I have a question for the brethren that use such sophisticated kit.

I used GW's calculators in Beer engine for both hydrometer readings and refractometer. They were as follows:

Hydrometer: 1.020 @ 74.5c post boil, adjusted to 1.044.2

Refractometer: 10.8 Brix adjusted to 1.042 sample taken from same trial jar.

The only thing I can account for in the difference is that I have not yet calibrated with distilled water but other than this should there be any other reason for the difference that I should be aware of?

[Kev888]

It could well be the uncalibrated refractometer; mine changed by a few points when i calibrated it.

Nothing is perfect though so there may be other influences: theres some debate about brix-to-gravity conversions, neither the hydrometer nor the refractometer are likely to be 'perfectly' accurate, and temperature compensation that far off the hydrometer's design temperature can also be a bit less precise. Also, this probably won't apply to you, but some people have used the wrong calibration for their hydrometer - some are designed for 20c and others for (IIRC) about 16c.

Cheers
Kev

[Martin G]

Yep, I had a similar experience. My refractometer (set with tap water) read 1.039 and the hydromter was 1.043, my hydrometer reads tap water as 1.004. A mate tested my wort with a calibrated hydrometer, 1.041.

[gregorach]

temperature compensation that far off the hydrometer's design temperature can also be a bit less precise.

Yeah, I've never found a hydrometer temperature compensation curve that actually worked worth a damn for more than 10 degrees off design temperature.

[DeadFall]

I got my cheap Chinese refractometer over the weekend and everything is either stuck or the refractometer is crap. It reads a shade over 1 with Edinburgh tap water, which is about what I'd expect. I suspect that I do have stuck ferments, the samples tasted sweet and it's been pretty cold where I do my fermenting. I'll get some aquarium heaters and some method of insulation sorted out next pay day. But I'll make some sugar solutions up and test how it performs later today. I'll use the g/l scale here as a guide. (My hydrometer went bang a few days ago...)

But what a revelation a refractometer is compared to a hydrometer, so much easier to use.

[Kev888]

But what a revelation a refractometer is compared to a hydrometer, so much easier to use.

Yes I agree, especially for testing the runoff during fly sparging.

That said, I'm more and more reverting to my hydrometer post-fermentation, as it just seems more easy/certain than the compensations the refractometer needs when there's alcohol in there.

Cheers
Kev

[AceMcAce]

It reads a shade over 1 with Edinburgh tap water

Buckfast?

[gregorach]

It reads a shade over 1 with Edinburgh tap water

Buckfast?

No, that's the west side of the country. I guess you have no idea how much difference that makes...

[gti1x]

We don't all drink Bucky here on the West - some of us drink Bells and Irn-bru!

GTI

[DeadFall]

Can you even buy Bucky in Edinburgh? Or do the neds lap it up too quickly?

[orlando]

Well I got some distilled water and the Refractometer was spot on 0. It claims to have built in temp correction so I now have to assume that it is the inherent difficulty of converting Brix to gravity. When I checked my wort coming to the end of fermentation the divergence was even greater. My Refractometer said it was 5% = 1.016 using GW clculator, Hydrometer was more like 1.011.

Finally down to 1.010 according to Hydrometer so I'm ignoring the Refractometer and going with that. Crash cooling to 6c then kegging tomorrow.