Refractometer

[NickThoR]

So... Im clumsy. I just broke my second hydrometer by knocking it and the tube of beer it was in on the floor. I always assumed refractometers were pretty expensive, but i found this one for under 20$ with free shipping.

http://www.ebay.com/itm/Hand-Held-F...SE-/291544034783?_trksid=p2141725.m3641.l6368

Has anyone by chance bought one of these? Im sure its china made whatever but It seems like it should work fine, and only 12 bucks more than the standard glass hydrometers. Any thoughts or suggestions?

 

[PapaFoxtrot]

This is the one that I bought a few years back. Works fine, but be advised that the inexpensive ones are graduated in Brix, not SG - so you'll need to do the conversion. No big deal, I have a spreadsheet that I use for brew day(strike water temp, etc) and I included the Brix to SG calc on it.

 

[flars]

You will still need a hydrometer for accurate measurement of FG. Refractometers don't work to well in the presence of alcohol.

My method for saving hydrometers. (Still have the first one purchased in the late 80's.)
The sample glass, for tasting, holds the sample tube and is in a quart size margarine container. The hydrometer rests in the margarine container. After testing the hydrometer goes back into the margarine container, it is never laid on a flat surface. Flat surfaces are never flat, and hydrometers roll very easy.

The real key is to never have the hydrometer anywhere near where you will be reaching, or moving, something over the top of it.

 

[Likefully]

You will still need a hydrometer for accurate measurement of FG. Refractometers don't work to well in the presence of alcohol.

Half true - at lower alcohol volumes the refractrometer will give you a reasonably accurate reading (but you need to some maths to get the FG), at higher alcohol volumes (from about 9% up) the alcohol starts to throw them off a bit.

Besides, I am not too fussed about getting a precise FG reading, what matters more to me is that i know it is terminal and the refractrometer can tell you that ... and all you need is a few drops of beer - thats the real bonus of them!

 

[NickThoR]

hmmm, i didn't know they weren't accurate. to what level are they not accurate?
As likefully mentioned, i am mainly looking to now when a beer is finished, but i would like to now reasonably close what the abv is, probably within at least half a percent. (ie, if i can say, this beer is 4.5-5% abv, thats close enough for me.)

 

[flars]

Half true - at lower alcohol volumes the refractrometer will give you a reasonably accurate reading (but you need to some maths to get the FG), at higher alcohol volumes (from about 9% up) the alcohol starts to throw them off a bit.

Besides, I am not too fussed about getting a precise FG reading, what matters more to me is that i know it is terminal and the refractrometer can tell you that ... and all you need is a few drops of beer - thats the real bonus of them!

It depends upon how accurate you need to be. With kegging there is no worry about bottle bombs.

 

[jrcrilly]

Be aware that some inexpensive imported units do have an SG scale, but it is incorrect. This is either because they were made for some other use, or (my theory) that someone in China made a huge batch of them with an incorrect conversion in the artwork and are dumping them on Amazon and eBay. You can tell; a good one will show 20 Brix in line with 1.083 SG. The "bad" ones show 20 Brix in line with 1.077 SG. 1.083 is correct.

 

[jrcrilly]

If you know the original gravity (either in Brix or SG) you can get a reasonably accurate FG from a refractometer by using one of the many online calculators out there. If you don't know the OG, the refractometer really comes in handy because you can derive a decent approximation of abv by plugging in both Brix and SG (from a hydrometer) into other online calculators. Can't do that with just a hydrometer.

 

[Blue-Frog]

Just to be clear...

The only problem with the "bad" refractometers is the SG scale readings?
The Brix scale can be trusted, and converted accurately to SG by some other chart, formula or program.

Is this correct?

and the 20 brix line-up at 1.083 SG. is the same thing as what Sean Terrill
is saying here, but perhaps less neatly:

For a quick check, look at what SG corresponds to 25°Bx.
It should be about 1.106.
If it’s more like 1.100, they used the “multiply by four” rule,
and the SG scale won’t be accurate above about 1.050.


jrcrilly;
To safe-en my search, could you cite one or two that you have in mind here? Thanks...

If you know the original gravity (either in Brix or SG) you can get a reasonably accurate FG from a refractometer
by using one of the many online calculators out there.

If you don't know the OG, the refractometer really comes in handy because you can derive a decent approximation of abv by plugging in both Brix and SG (from a hydrometer) into other online calculators.

 

[jrcrilly]

Yes, the ones with the incorrect conversion still read Brix correctly (at least, the one I have does). Sean is describing a different situation, which I haven't seen. Refractometer users generally do the conversion in their heads, by multiplying the Brix by 4 and then dividing by 1000 and adding 1. Thus, a reading of 10 Brix would translate to an SG of 1.040. As the Brix reading approaches 15, this approximation begins to accumulate errors. That's why 20 Brix is 1.083 rather than 1.080. The units I have seen are worse than what Sean describes because they apply the correction, but in the wrong direction!

Here's a calculator for converting a post-fermentation refractometer reading to FG and abv.
http://www.brewersfriend.com/refractometer-calculator/

 

[Likefully]

. As the Brix reading approaches 15, this approximation begins to accumulate errors.

My understanding is the brix reading becomes less accurate (reliable) the higher the alcohol content of the beer. Alcohol changes the way the light refracts (something like that) and therefore affects what you see on the scale.

In my experience there is hardly any noticeable difference between using a refractometer (and the conversion) and a hydrometer for beers up to about 6%. I made a 11.5% stout a while back and the difference between the hydromoter reading and the refractometer reading was about 1% ABV.

 

[DU99]

http://www.brewersfriend.com/brix-converter/ i use this