# High FG

### Help Support Homebrew Talk:

#### bobtheUKbrewer2

##### Well-Known Member
My FG's are usually 5 to 5.2 BRIX. Today I was chatting to the chief brewer at my local microbrewey, and he said they usually get down to 2.0 to 2.5

My refractometer reads 0 with tap water, but to eliminate refractometer problems, can someone tell me how much sugar per litre to read 2,3,4,5 BRIX

assuming the refractometer is ok, any thoughts on why I am not getting below 5

I buy crushed pale malt and mash at 67 to 69 deg C for 1 hour. I use safale 04 yeast. Thanks.

#### ajf

##### Senior Member
You can't get a true Brix reading with a refractometer after fermentation has started.
The alcohol causes the refractometer to read high.
You can use the refractometer to determine when fermentation has finished (the reported Brix reading will stop dropping when it's done).
But to get an accurate final gravity, you need to take a hydrometer sample.

-a.

OP
B

#### bobtheUKbrewer2

##### Well-Known Member
thx - BUT the brewery measures BRIX they get 2 I measure BRIX and get 5 to 5.2

I dont want absolutes - I do use a spreadsheet to take account of alcohol

ANYWAY - the hydrometer is floating in alcohol solution mixed with maltose solution, with a hydrometer u should add 0.004 for an approx 4% ABV beer

#### ajf

##### Senior Member
How does the brewery measure Brix? I suspect they use a hydrometer or saccharometer , which measure specific gravity, rather than refractive index.
If the brewery is truly measuring Brix, which is defined as 1 gram of sucrose in 100 grams of solution, then their fermentation is not finished as sucrose is 100% fermentable.
I gave up on using a refractometer to estimate the FG many years ago, when the Promash calculator proved to be so unreliable.
I recently brewed a beer that had an OG of 1.0567 (14.40 Brix). I measured the OG with both a hydrometer and refractometer.
After fermentation was complete, I measured the FG with both a hydrometer and refractometer. It read 6.7 Brix and had an FG of 1.0085.
Using Sean Terrill's calculator it predicts an FG of 1.0111 (2.6 points off).
Using the Promash equivalent, it predicts an FG of 1.00811 (0.39 points off).

-a.

OP
B

#### bobtheUKbrewer2

##### Well-Known Member
the brewer was very specific - they use a refractometer. Actually he told me to bring a sample of my next all grain wort and my refractometer, and we would compare both instruments.

#### bryancorbett2

##### Well-Known Member
that place sounds pretty cool if he is willing to do that!

#### ajf

##### Senior Member
I don't doubt that the brewery uses a refractometer to get an idea of the gravity before fermentation has started as the two instruments are comparable in accuracy, but I don't think they will use a refractometer to judge the final gravity. He asked you to bring a wort sample, not a beer sample. By definition, wort is unfermented so you will not be able to compare the finished beer with the two refractometers. Ask him specifically how they measure the FG.

-a.

OP
B

#### bobtheUKbrewer2

##### Well-Known Member
the purpose of taking my refractometer to the brewery is to compare the 2 instruments, I will take unfermented wort and they will produce some finished beer so as to do the comparison on that. They only use a refractometer and this itself is calibrated against the annual laboratory tests for ABV that they have to carry out to comply with UK law.