Yet Another Fg, Hydrometer/refractometer Thread

[vykuza]

Hi everyone,

I've had something interesting happening with my latest BIAB brew. I made one of Ross' Nelson Sauvin Summer Ale (in a half size 12L batch) and have a puzzler of an FG problem. It's been in the fermenter for 2.5 weeks, about 1 week in it hit 1.020 and stuck. (OG was 1.045). Beersmith gave me an estimated FG of 1.013, so I tried to get it lower.

I went through the usual moves, some yeast nutrient, swirling, stirring, raising the temp and a small hit of simple sugars. Nothing. Nada. Zip. Zilch. 1.020 it was. I measured this with my new refractometer, and recalibrated it after all the kerfuffle. 1.020.

I figured it wasn't going any lower, so today I bottled in 6L tap-a-draft big brown bottles, with plenty of headspace in case it took off again. Out of interest, I took a sample and measured it with my old hydrometer, and got a 1.011. Who's telling fibs here?

I picked up a refractometer because I am pretty down on the hit-and-miss measurements I've had in the past with a hydrometer. But could I be barking up the wrong tree? Both measure 1.000 in water, by the way. How else could I go about checking their accuracy? Any way of creating a known SG liquid accurately?

 

[raven19]

100grams of DME in 1L of water will give you 1040 iirc.

Refractometer takes only a small sample size, hence could be distorted.

Others suggest using a Refractometer for Brew Day, then Hydrometer once in the Fermentor.

Personally I broke my last hydrometer, now only havea Refractometer, and its great.

Maybe take 2 or 3 samples each time to check for accuracy of reading...?

 

[Adamt]

Hi everyone,

I've had something interesting happening with my latest BIAB brew. I made one of Ross' Nelson Sauvin Summer Ale (in a half size 12L batch) and have a puzzler of an FG problem. It's been in the fermenter for 2.5 weeks, about 1 week in it hit 1.020 and stuck. (OG was 1.045). Beersmith gave me an estimated FG of 1.013, so I tried to get it lower.

I went through the usual moves, some yeast nutrient, swirling, stirring, raising the temp and a small hit of simple sugars. Nothing. Nada. Zip. Zilch. 1.020 it was. I measured this with my new refractometer, and recalibrated it after all the kerfuffle. 1.020.

I figured it wasn't going any lower, so today I bottled in 6L tap-a-draft big brown bottles, with plenty of headspace in case it took off again. Out of interest, I took a sample and measured it with my old hydrometer, and got a 1.011. Who's telling fibs here?

I picked up a refractometer because I am pretty down on the hit-and-miss measurements I've had in the past with a hydrometer. But could I be barking up the wrong tree? Both measure 1.000 in water, by the way. How else could I go about checking their accuracy? Any way of creating a known SG liquid accurately?

Once your brew starts fermenting (and alcohol is in the beer) you need to compensate for this with your refractometer reading, have you done so? It's not clear from your post but I'm guessing not.

 

[Fourstar]

when reading with a refrac you need to account for the alcohol in solution (light density changes)

See link:
http://brew.stderr.net/refractometer.html

E.g. if you have a beer with an OG of 1.050 and your reading is say 7brix, it is not actually 1.028, but 1.014 due to the alcohol content.

 

[vykuza]

Once your brew starts fermenting (and alcohol is in the beer) you need to compensate for this with your refractometer reading, have you done so? It's not clear from your post but I'm guessing not.

Considering I've never heard of that, you can be very sure I haven't been compensating for alcohol content in the beer. How do I do it? Instructions that came with the refractometer don't mention it at all.

 

[Fourstar]

Considering I've never heard of that, you can be very sure I haven't been compensating for alcohol content in the beer. How do I do it? Instructions that came with the refractometer don't mention it at all.

see my link or use beersmith (i think promash can do the calculation too)

 

[Maple]

Considering I've never heard of that, you can be very sure I haven't been compensating for alcohol content in the beer. How do I do it? Instructions that came with the refractometer don't mention it at all.

There is a spreasheet on here somewhere, I'll see if I can dig it up, but it was posted by one of the guru's on AHB. Things started making a whole lot more sense after I started using this.

Edit: found it

 

[HarryB]

http://www.primetab.com/formulas

if you want the actual formula

 

[raven19]

Aaaah! There is the issue then.

Will look for a linky to some relevant threads.

Beersmith has a good tool for taking into account alcohol, and there are also some online webpages too.
Edit - Linky to thread

 

[vykuza]

You guys are the best :super:

Having a play with Beersmith's refractometer tool now. This makes a lot more sense now!

Thanks very much!