Milk Stout refractor reading vs Beersmith calculation

Brewing Processes
1

My refractor is reading 1.116 SG1.028 FG. BeerSmith calculated 1.065/1.016 – By refractor says 13% where BeerSmith says 6.5%–a big difference. Any ideas on the major difference.

Thanks

2

Beersmith’s FG prediction is inaccurate in my opinion. I’ve sent Brad a note asking about it. Maybe it’s me.

BeerSmith’s OG estimate is based on your equipment profile. If it is not dialed in it will be inaccurate. Measure volumes accurately, use a hydrometer to get OG for a few batches to get estimated efficiency, etc.

I recommend using a hydrometer or refractometer to get OG. However, if you’re using a refractometer to get FG it will also be inaccurate due to the alcohol present. A more accurate measurement will be a finish hydrometer. I believe there’s a conversion calculation to use a refractometer for FG but I’ve never used it.

1 Like
3

Thanks Dwain
In the past, my refractometer has been acceptable for my use (order of magnitude). I have an app to convert FG. The refracto is generally close to Beer Smith’s numbers for the OG and in the neighborhood for FG for my IPA, PA, some belgians, blonds,“regular” stouts/porters, etc. This beer is a holiday beer so amping up the flavor. Did not know if the added juice, brandy and lactose was messing with the numbers. Appreciate your response.
Betty

4

1.116 vs 1.065 is a huge disparity in gravity.

Did you double check the 1.116 reading with any other instrument? How often to check the calibration on your refractometer? Was your post-boil volume off significantly? Are there sugar additions that aren’t factored into the calculated 1.065?

1 Like
5

No, I did not back check against any other instrument. The last time I used the refracto was a couple of weeks ago for a biere de gard and the numbers were right on. I made 2 batches of the milk stout and the numbers for Batch 1 and Batch 2 were identical- way high. I plugged every ingredient into the software. I am at a loss.

6

Possibly the added Brandy threw it off. I don’t think unfermented juice would but I guess it could

1 Like
7

I have also had variations with BS3 FG calculations. But not nearly as far off as Identified here in this thread.

Also, I use a refractometer for “basic” readings while sparging and during the boil. Then, after the boil I measure the SG as well as the FG with a calibrated hydrometer. Personally, I would never trust a refractometer on a fermented beer. That’s just me.

1 Like
8

If software accurately predicts your FG, it’s a fluke.

2 Likes
9

Some questions and comments:

  • Are you reading s.g. directly from the refractometer, or Plato? The specific gravity scale is off on pretty much all refractometers out there, so I always measure in Plato/Brix and then convert.
  • That said, the above issue won’t account for what you mentioned. I would recalibrate (plain tap water is fine - make sure you are zeroed out) and see how your next batch reads. I always calibrate my refractometer multiple times; it doesn’t take long, and is a cheap insurance policy against bad measurements.
    • A quick test with plain tap water should read 1.000, and it is reading way high that may explain your problem right off the bat.
  • I suppose it’s possible your gravity is just super high…but not likely?
  • The f.g. on BeerSmith (and probably pretty much all software) is of variable utility. For a down-the-middle grain bill with an “average” mash temperature that has minimal unfermentables, I get pretty accurate estimates. For anything that involves a lot of crystal/roasted/unfermentable grains, you’ll end up with a mismatch on the final gravity.
    • For example:
      • A pilsner I did with 94% pilsner malt and 6% melanoidin+carapils predicted f.g. of 1.010 and hit an actual of 1.011.
      • An American stout with 81% 2-row+Maris Otter and 19% crystal/caramel/roasted predicted an f.g. of 1.013 and had an actual f.g. of 1.021.
    • At some point I should probably work out an equation for this correction, but that’s a problem for future me (or someone else).
1 Like
10

I am reading directly from the refractometer then use an app to convert abv. I am thinking the gremlins were out for this recipe. I am a small batch brewer; between not wanting to “waste” as much beer using a hydrometer or introducing another variable for contamination I have just wanted a general idea of the alcohol level.

1 Like