Can you use a refractometer for both OG and FG measurements?

I just took a reading on my batch a few minutes ago. It's been about 9 days and airlock activity has stopped and the krausen has fallen. To my dismay my FG is WAY off the mark. My OG was 1.055 and currently it's at 1.024. I used my new refractometer that I got for XMAS for both readings. I believe I came across something a few weeks ago that mentioned them not working well to learn your "true" FG measurements. But maybe it's just hopeful thinking at this point. I did calibrate it with distilled water if anyone is wondering.

Any insight on this?

Side question: If it doesn't drop in the next week anymore will it be drinkable? I have never had a beer that far off. I assume it's going to be really sweet.

Thanks

 

If you've got a hydrometer then can you use it to take a reading and compare? If not then maybe get one because it's always good to have a few sources for results just incase you're unsure on the accuracy.

 

No, not final gravity as the alcohol causes problems. There is a paper or thread that explains it somewhere on the site. If I find it, I'll link it.

 

Alcohol changes the refractive index, so you can't get a correct reading, no. That's why it seems so high.

Either use a hydrometer, or there are conversion formulas out there. Sean Terril's calculator was at one point the go to http://seanterrill.com/2012/01/06/refractometer-calculator/

But I think there are newer options out there.

I don't ever use a refract cold side, so I have no experience or opinion on the options. But people swear by them. Personally I'd rather read directly and not use a calculator.

There are other options out there beyond hydrometer and converted refract reading. Some high tech gizmos marketed to homebrewers, and some higher tech ones used by pros (the latter tending to be prohibitively expensive, although Anton Paar makes a density meter geared to nanos and rich gadgety homebrewers).

 

That was the link I just found, beat me to it

 

I use one for both because I make small 2G batches and like that a refractometer only needs a few drops. For FG I use the calculator linked above to correct for alchohol presence. Brewers Friend also has one. At bottling time I often use my hydrometer to take a reading with some of the extra beer that is not enough for a bottle and have actually found the result (in my case) to be very close to the corrected refractometer reading.

 

I only use the refractometer for OG and FG. Works great and doesn't waste any beer. The online conversion tool (Brix WRI) on Brewers Friend is easy to use. Just make sure you're putting in Brix.

 

A refractometer may be used for both OG and FG. When I first started using mine years ago I compared the hydrometer and spectrometer for every batch I made and not once had a discrepancy, so I no longer use the hydrometer. However, I will note that I use the "refractometer tool" in BeerSmith to do this. There are no manual calculations required. I select "fermenting wort gravity" and enter the OG. I then take a current reading of the fermenting beer and record the brix. I enter that number and get the current gravity. It's that easy.

 

I've been doing the same. Took out my hydrometer to compare with refractometer after 5 batches and they were still in line.

+1 to the ease of use of the BeerSmith tool

 

I personally agree with @MrHadack too. I'm not going to even try to argue with the research and information from Sean Terrrill's site or the many others on this forum that will tell you how and why it cant be done.

My personal experience from my own testing with side-by-side measurements with my refractometer and hydrometer samples tell me that they are the same.

You do need to use a conversion calculator for FG. I cant speak to the BeerSmith tool but the one I use is here: http://onebeer.net/refractometer.shtml
In fact, I've found the results from Sean Terrills tool to disagree with my hydrometer. Again, just my findings...


Whatever the case, this is what works for me and I love the simplicity of the refractometer and greatly reduced waste of beer from testing.. (yes, I will drink the hydrometer sample but it can be pretty yeasty till its done! lol)

 

I appreciate everyone's help! What a relief!

 

No

The refractometer uses light and a prism to measure the ratio/density of sugar to water in a liquid - more sugar/higher reading (pre-fermentation) means it will be a boozy beer. Once alcohol is introduced to the solution, it skews the measurements, however there are formulas and websites you can use to help you convert pre and post fermentation if you only want to use a refracto.

This one i've used before: https://www.northernbrewer.com/pages/refractometer-calculator

You should keep a hydrometer handy and double check any refraco readings that you take pre or post.

 

Is it possible to match up the SG and FG gravity readings with the Brix side? If so it looks like I was around 14 Brix and now 8 Brix which would put me at a 1.016 FG.

I was shooting for 1.010 to 1.015 so that's well enough.

 

The question has been answered but....
yes it can with the conversion.
I recently got a refractometer, I've used it on a couple batches so far, backing it up with my hydrometer. So far, plugging it into the conversion thing I found has matched up within .002 or so, so I'm calling it good. I'll double measure a couple more batches to make sure though.
The one I use is on the Brewers Friend site
https://www.brewersfriend.com/refractometer-calculator/#
There's also a pretty god article about using them.

 

Sorry I think I was confused on the conversion part (FG to Brix) in regards to just looking across the refractometer scale. Not using any kind of calculator. And ya I am glad I posted as now I know I can use the tool throughout the entire process (thank you) as the waste of beer using the hydrometer sucks.

 

Interesting thread. When I got into brewing a year ago, I read that it cannot be used. Now it looks like you can, with a conversion. In retrospect, I wish I had bought a refractometer last year instead of a Wine Thief. Now that I'm getting into BIAB, I'll be getting one anyway. It'll be nice only wasting a few drops of wort.

 

When starting out homebrewing, there can be advantages to starting with a single source of well curated information (aka a book). For example: HtB, 4e, appendix A covers how to use refractometers to measure FG "with a reasonable degree of accuracy". Obviously, no single source of information is 'perfect' and home brewing changes (slowly) over time.

It may also be possible that there are specific brands / models of refractometers that don't work well with wort / beer.

 

Quoting myself... Strange... LOL

I just wanted to report that I have looked at the BeerSmith tool while entering a fermentation progress sample and found it to match the onebeer.net site exactly!

I have to say that I'm sold on this BeerSmith feature now!

 

Mobile app Brewzor Calculator.... It's a pretty good mobile app for brewing.

 

It also has a starting gravity reading from finished beer. You would use it dial in the parameters a little tighter.

 

Not to beat a dead horse, but...
The presence of alcohol in fermenting beer will impact a refractometer measurement in a specific, repeatable manner-- the same as how temperature differences will impact a hydrometer reading in a specific, repeatable manner. In other words, a conversion formula is all you need in either situation. Physics / chemistry isn't going to fluctuate batch to batch, and the readings obtained with each (following the proper procedure) are equally accurate.

Honestly, I think we're all saying the same thing is this thread. That is:
A hydrometer will take accurate readings when compensating for temperature of the sample.
A refractometer will take accurate readings when compensating for the presence of alcohol.
One of the great things about brewing is that, in controlled situations, results are extremely predictable. X + Y will always result in Z, provided X and Y are accurate / on target.

 

I do think there might be Brix difference in the extremes like 100 pilsner vs a stout wort.


If you know you're gonna take multiple readings along the way. It's good to do both just to calibrate.

I used to just take readings at mash time to verify my extraction. Then let's it go three weeks. Now that I plan to spund its more important to take small readings every day with a fast ferment test.

Worthwhile reading...
http://beersmith.com/blog/2010/11/02/how-to-use-a-refractometer-brix-and-beer-brewing/

 

* sorry - kind of high jacking the thread - i'll leave this here and make another post

Looks like I need my own advice

I've had 15g of a blonde fermenting for like 2 weeks, and made one of them into a raspberry blonde.

I took a couple readings with my refractometers as my hydrometer broke in between readings. I also suspect that it was broken on brew day as I noticed a couple of cracks and water leaking into the area where the weight is toward the bottom.

The issue is that just now I only took reading with my refracto, and the final readings are 1.012 (about 3 Brix); on my brew log I have 1.045 as (I THINK) post-boil original gravity/reading (about 10.5 brix)

When I plug the numbers into a calculator I get an ABV that doesn't make sense

With this calc: https://www.northernbrewer.com/pages/refractometer-calculator
I get 6.4 abv

while here :
http://seanterrill.com/2012/01/06/refractometer-calculator/
I get 5.1

Its meant to be a low abv beer, so i'm leaning toward the later

Any ideas?

 

Sorry to wake up an old post, but I have found some issues using the onebeer converter.

Being European, I will typically use a decimal comma instead of a decimal point.

However when using the onebeer converter, this is apparently of some importance.

Entering a Original Brix of 12.25 and a Final Brix of 6.5 and varying the usage of decimal commas and point, I get the following table:
OB = 12.25; FB = 6.5; FG=1.01096; ABV = 5.09
OB = 12,25; FB = 6,5; FG=1.00851; ABV = 5.27
OB = 12.25; FB = 6,5; FG=1.00787; ABV = 5.48
OB = 12,25; FB = 6.5; FG=1.01159; ABV = 4.87

As you can see, two apparently identical values result in four somewhat different values. Does anyone have an explaination as to what is the reason. And which value should I trust?

I did a quick check with Sean Terrill's converter and the NB converter. Terrill's has the same bug. NB will only allow me to type in decimal points.

Thanks in advance.

 

I would trust the results when using a decimal point instead of a decimal coma. There are probably some folks on this forum that can explain the problem on a technical level but it looks like an input validation bug of some sort. It seems NB is doing the right thing by rejecting the decimal comma.

EDIT: Doing a little research,this is an input validation bug. Or rather, the tools aren't masking the "decimal comma" as the intended decimal point. It seems that the "decimal comma" is being interpreted as a thousand separator.
e.g. 12,25 is being interpreted as 12,250.00

 

I think you are closer than I am to the right answer, however, I just checked your hypothesis without any , or .

Here the values are, understandably, off the charts.

 

I bought 3 hydrometers - I'm going to put the refracto on the shelf for a while

Brewed a couple of batches since then - all spot on with the ol trusty hydro