Refractometer

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beersoulman

Refractometer

Post by beersoulman » Wed Feb 01, 2017 4:18 pm

Anyone got anything good to say about these? I'm going back to hydrometer after really low readings on my wort.


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chefgage
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Re: Refractometer

Post by chefgage » Wed Feb 01, 2017 4:29 pm

I have only tried mine once and like you got a low reading compared to my hydrometer. But I had not calibrated it. I have now got some distilled water for zeroing it and some dme. I will take various readings at different SG using the hydrometer as a comparison to get the correction factor needed. This can then be pit in beersmith when taking readings. Hopefully this will sort things out. Did you calibrate yours?

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Re: Refractometer

Post by oldbloke » Wed Feb 01, 2017 5:27 pm

My refractometer agrees with my back-of-envelope known-sugars calcs better than my hydrometer does.
But I rarely use either. Exact ABV isn't that important to me. I just make sure I have enough sugars in whatever I'm making to get where I want.
Last edited by oldbloke on Wed Feb 01, 2017 6:43 pm, edited 1 time in total.

Matt in Birdham
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Re: Refractometer

Post by Matt in Birdham » Wed Feb 01, 2017 6:10 pm

beersoulman wrote:Anyone got anything good to say about these? I'm going back to hydrometer after really low readings on my wort.
I use my refractometer all the time and it always agrees with my hydrometer. Perhaps you got a dud, or it needs calibration?

I do still take one hydro reading at pitching, just because, really. I use the refract during fermentation too and adjust with an online calculator. The times I have tested this it has always been bang on, so I very rarely use the hydro now after pitching.

When they are working, I find refracts way more convenient to use, especially during the brewday.

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Re: Refractometer

Post by guypettigrew » Wed Feb 01, 2017 6:40 pm

+1 to Matt in Birdham's comment.

The refractometer takes a tiny amount of liquid so if you're checking the gravity of hot wort it takes no time at all for the refractometer to cool it down.

I always use the Brix scale on mine and convert it to gravity using this online calculator .

Guy
Last edited by guypettigrew on Wed Feb 01, 2017 10:14 pm, edited 1 time in total.

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Kev888
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Re: Refractometer

Post by Kev888 » Wed Feb 01, 2017 8:27 pm

Refractometers need to be calibrated before use, with water or distilled water. Even then though, they don't 'quite' give the correct reading, as they know nothing of (and so cannot account for) the make-up of the wort, which is not simply sugar-water. If you want to be precise about it then a small correction factor needs to be applied to their reading, which may be different for different worts. BUT the cheap chinese ones aren't especially accurate and can be hard to read precisely too, so for normal and lower gravity worts it may not be worth getting too hung up with precise correction factors.

As to agreeing with hydrometers, a lot of those are not especially accurate either, so agreement or otherwise means very little except as a rough sanity check of readings. Some hydrometers can be calibrated by (gently) tapping to move the paper scale up or down, and improved by testing wort at the correct temperature rather than compensating (with tables or calculators) for other temperatures, but even then the typical home-brew types are not hugely precise instruments - unless you happen to get a good one. If everything is in reasonably close agreement, it probably isn't broken.

Additionally, refractometers are fooled if there is any alcohol present, so (even with a wort correction factor) they are not accurate after fermentation has begun. There are calculators to help overcome this and to a degree they can, but methods/formulas vary and there are different results from different calculators. There are also apparently built-in misunderstandings or disagreements even on how to convert correctly between the different scales used. For our purposes, if the calculated result is roughly in agreement with a trusted hydrometer then thats probably as good as its likely to get.

Personally, I use a decent hydrometer for all my readings except when I want to quickly sample hot wort, as cooling a tiny sample is much easier. In some situations, such as the run-off from a fly-sparge, the refractometer is a great tool - things are changing minute by minute, so delays are unhelpful, and precise readings aren't needed as the minimum gravity is not a black-and-white figure to begin with.

Thats all very general, but without knowing 'how' low the refractometer readings are, and how accurate the hydrometer is, its a bit hard to say whether the OP is describing something normal or if its extreme.
Kev

beersoulman

Re: Refractometer

Post by beersoulman » Wed Feb 01, 2017 9:27 pm

Wow! Thanks for detailed replies! It's only a cheap Chinese one .. and I thought I could take original and final gravity with it. It it seems not. I've been using hydrometer for 40 years and have got quite intuitive about there behaviour . I only want to know strength within .5 percent and I reckon hydrometer and experience gets me there . I just thought the refractometer would be more convenient and sterile . Looks like I'd need 40 years to get used to its foibles and I don't think I'll live that long ! Thanks everyone


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tourer
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Re: Refractometer

Post by tourer » Wed Feb 01, 2017 10:10 pm

Checked mine with RO water a couple of days ago and it was out by 3 points. Adjusted it and i was a bit disapointed with the OG but thats down to me.

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Re: Refractometer

Post by chefgage » Thu Feb 02, 2017 9:55 am

When i first got mine i checked the zero with just tap water and if i remember correctly it was about 4 points to high. So i zero'd it and then used it to measure the SG pre boil and the the SG post boil and both times it was a lower value than the hydrometer by about 5 points.

Like Kev888 said the hydrometer is probably not that accurate but its what i have been basing all my brews on. With this in mind i am going to calibrate it properly with DME and distilled water and then appyly a correction factor to it so it tallies up with my trusty (cheap :) ) hydrometer, because i do like the idea of being able to quickly take lots of gravity readings throughout the process

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FUBAR
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Re: Refractometer

Post by FUBAR » Thu Feb 02, 2017 11:20 am

I never use a hydrometer now as my refractometer in conjunction with online calculators always agrees with readings taken with a variety of hydrometers at all stages of brewing right up to FG. It is so much easier to sanitise a pippet and just bin it afterwards.I certainty don't miss the faffing around sanitising a hydrometer and trial jar and cleaning afterwards everytime a gravity check is done.
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oldbloke
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Re: Refractometer

Post by oldbloke » Thu Feb 02, 2017 11:43 am

FUBAR wrote:I never use a hydrometer now as my refractometer in conjunction with online calculators always agrees with readings taken with a variety of hydrometers at all stages of brewing right up to FG. It is so much easier to sanitise a pippet and just bin it afterwards.I certainty don't miss the faffing around sanitising a hydrometer and trial jar and cleaning afterwards everytime a gravity check is done.
I only give the hydrometer and trail jar a quick rinse as I don't return the sample to the fv: too risky, just drink it.
The turkey baster I draw off the sample with gets boiling water through it though

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