Fermentation stuck or refractometer weirdness?

[benoj]

Hey all,

I have a NEIPA which started of fermenting VERY actively. The OG was 1.080 measured with a hydrometer. I have been dry hopping this week and took a measurement with my new refractometer - it shows that the current gravity is 1.035 - however I would have expected to hit my FG of 1.018 by now (day 9).

I had a look around and saw a few things saying you _can't_ measure FG with a refractometer. Is this true, should I take a new reading with my hydrometer or is that just hopeful?

Thanks,

Ben

 

[LittleRiver]

The presence of alcohol throws off refractometer readings. There are online calculators that will compensate, or just use a hydrometer.

Use the refractometer on brew day to measure OG, before there is alcohol present.

 

[Yooper]

Right- alcohol skews the refraction of light, which is what a refractometer measures. Use the above calculator to get a decent estimation of the FG (it's in the Part II portion).

 

[ravhawk2000]

Just my own 2 cents worth, hydrometer is always the best option I've ever either used or seen used by breweries. That's really your best best.

 

[VikeMan]

Just my own 2 cents worth, hydrometer is always the best option I've ever either used or seen used by breweries. That's really your best best.

Lots of comm'l breweries use refractometers. I've been fortunate to look under the hood of many, and I can't recall one that didn't use refractometers, at least in some situations.

 

[ravhawk2000]

Maybe, but a lot of people on both sides use both first of all. 2nd, once fermentation begins, the refractometer is far less reliable. But tbh, its really to each their own. Plus its looks like you know what your doing holding a refractometer vs a hydrometer, lol.

 

[dmtaylor]

Refractometers are quite accurate for FG if you use the right equation. The best one is Brewer's Friend, linked above by @LittleRiver. Based on my last ~20 batches, I find it averages within 0.002 of a hydrometer which is close enough for most intents and purposes. And if you're crazy about calibrating both your hydro and refractometer before and after every use like I tend to do, then I was able to bring that average error lower than 0.001. Good enough for me.

A ton of great discussions as well as my standard guidance for anyone interested in using refractometer for FG:

https://www.homebrewersassociation.org/forum/index.php?topic=28544.15

The OG was 1.080 measured with a hydrometer. I have been dry hopping this week and took a measurement with my new refractometer - it shows that the current gravity is 1.035 - however I would have expected to hit my FG of 1.018 by now (day 9).

Using Brewer's Friend, it looks to me like your FG is closer to 1.010:

 

[benoj]

Hi all,

In the end I used a hydrometer to check this and it was .1012!

Thanks for the help - beer is conditioning well and looking forward to trying it

Ben