Refractometer, Hydrometer, Gravity.... Oh My!

[kirbcheck]

First, I wasn't sure if this belonged in Brew Science or Fermentation as it is directly related to Fermentation.

Here's the situation.

A few weeks ago I brewed a DIPA. This is also my first brew using my new refractometer. Post boil I had a gravity reading of 1.07 with my calibrated refractometer.

At 10 days I had a gravity reading of 1.02 with the same refractometer. I added 1.5# of sugar, a week later it was at 1.035. I checked every couple of days the same way. Gravity never changed. I freaked out thinking I had a stuck fermentation that was way too high.

I had read that amylase would drop it. So I said "What the hey, I'll do anything!" so I added it in the directed manner. It was 1.5 Teaspoons per 5 gallons. Which in a few days dropped it to 1.031. Where it's stayed.

After adding the amylase I got a feeling that I acted too hastily. Not enough research prior to action. After actually researching, I now KNOW I did.

I've since learned that alcohol makes the reading on the refractometer unreliable. So I dusted off my hydrometer, calibrated it then took a reading.... the gravity read 1.003... OOPS!

What's the best way to reliably use refractometer readings for post fermentation readings?

 

[schematix]

What's the best way to reliably use refractometer readings for post fermentation readings?

Put it on the shelf and get a hydrometer.

 

[day_trippr]

[...]What's the best way to reliably use refractometer readings for post fermentation readings?

Use a correction calculator, like this one...

Cheers!

 

[pdxal]

I like Sean Terrill's refractometer correction calculator:
http://seanterrill.com/2012/01/06/refractometer-calculator/

 

[hottpeper13]

My order of the day would be to make 5.25 gal min. in primary so you have enough to take the correct samples. My 65$ tool sits on the shelf too.

 

[kh54s10]

Use the hydrometer post fermentation!

 

[jddevinn]

Refraction adjustment calculations use a constant that is beer dependent. I use a refractometer post fermentation only on recipes that are proven repeats that I have calculated the correct wort correction factor for.

 

[schematix]

You can use it to reliably to check for change, but its a crap shoot as far as an accurate measurement.

I only use mine to check pre-boil gravity to make sure i don't have any gross efficiency errors. After that i get out the lab grade precision hydrometers.

Those compensation calculators will get you close, but don't be surprised if a hydrometer disagrees by up to +/- 5 points.

 

[jeremy0209]

I only use mine to check pre-boil gravity to make sure i don't have any gross efficiency errors. After that i get out the lab grade precision hydrometers.

Those compensation calculators will get you close, but don't be surprised if a hydrometer disagrees by up to +/- 5 points.

^^^This^^^

I use my refractometer to get a good idea of what's going on after the mash and during the boil, but my hydrometer has the final word on OG and FG.

 

[jerbrew]

Get something like this.

https://www.williamsbrewing.com/BREWERS-EDGE-BOTTLING-HYDROMETER-P529.aspx

 

[schematix]

I've got 3 narrow range precision hydrometers that I use. Only regret is i didn't buy these day 1 (about $100 for all 3).

1. Final FG Hydrometer (0-8.5 Plato, readable to 0.1 Plato)
2. Mid Range Hydrometer (7.5-16.5 Plato, readable to 0.1 Plato)
3. High Range Hydrometer (16-23.5 Plato, readable to 0.1 Plato)

They all have a built in thermometer with correction offset right on them. They are extremely accurate. I made several calibration solutions and they were all dead on at reference temp, colder, warmer, and even in the crossover range they matched each other. There is also a mark on the hydrometer where the top of the paper strip should be so if it ever slips you'd know right away. Love them.

 

[jerbrew]

I've got 3 narrow range precision hydrometers that I use. Only regret is i didn't buy these day 1 (about $100 for all 3).

1. Final FG Hydrometer (0-8.5 Plato, readable to 0.1 Plato)
2. Mid Range Hydrometer (7.5-16.5 Plato, readable to 0.1 Plato)
3. High Range Hydrometer (16-23.5 Plato, readable to 0.1 Plato)

They all have a built in thermometer with correction offset right on them. They are extremely accurate. I made several calibration solutions and they were all dead on at reference temp, colder, warmer, and even in the crossover range they matched each other. There is also a mark on the hydrometer where the top of the paper strip should be so if it ever slips you'd know right away. Love them.

Can you share where you got that set?

 

[schematix]

Can you share where you got that set?

LHBS.

I think this is what they are: https://www.fishersci.com/shop/prod...ined-form-brix-sugar-hydrometers-10/p-4414447

I'll have a look when i get home later and see if there is a part number on them. I paid like $35/$35/$30 for the low/med/hi range.

 

[jerbrew]

awesome, thanks i'll shop around I could use a good high gravity hydrometer.

 

[schematix]

I'm trying to find exactly what I have but having a hard time. These are the same hydrometers but mine did not come with the NIST certificate. Maybe if you look hard enough you can find someone selling almost the same thing at a lower price point.

Here is a link to the set on amazon: https://www.amazon.com/dp/B00YYLURQI/?tag=skimlinks_replacement-20

Individual models:
2515SB - FG hydrometer
2516SB - Mid range
2517SB - high range

 

[kirbcheck]

Thanks everyone. Lots of good stuff here. For now I will use the refractometer for monitoring change. Then when everything stops I will take an actual hydrometer reading. Now the question of the day. Should I rebrew the same recipe without dropping it out to 1.003...?

 

[jddevinn]

Assuming that you had enough amylase extracted from the grain adding more shouldn't do much to further the fermentation.

I originally missed that you added sugar. Was this because you thought it was stalled or because it was part of the original recipe? How large was the batch size?

 

[kirbcheck]

Assuming that you had enough amylase extracted from the grain adding more shouldn't do much to further the fermentation.

I originally missed that you added sugar. Was this because you thought it was stalled or because it was part of the original recipe? How large was the batch size?

I typically design recipes in a formulaic manner. I always add 1-1.5# of sugar per 5 gallons of DIPA. To dry it out.

 

[kirbcheck]

Quick update for those with interest, the beer is better than I expected, but that's not saying much. It's obvious it would have been better had I not dropped it so far. That being said, I plan to drink it.