Hydrometer Adjustments

[Bottoms_Up]

I was wondering if anyone adjusts their Final Gravity readings when using a refractometer? There is a significant difference between the measured reading and the actual reading of the beer gravity when using a hydrometer.

 

[Kickass]

If you’re using a refractometer for FG, you need to use a correction calculation. Otherwise, it’s inaccurate.

 

[mac_1103]

For instance. Personally, I find it easier to just use a hydrometer for my FG readings. It's not wasteful since I'm going to taste it anyway.

 

[IslandLizard]

I was wondering if anyone adjusts their Final Gravity readings when using a refractometer?

Not just for final gravity readings.
As soon as alcohol is present in your sample, a refractometer correction formula is needed. This due to alcohol having a much lower refractive index than water. The higher the fraction of alcohol in your sample, the larger the difference between the reading and the corrected (accurate) value.

Here are some refractometer correction calculators:
https://www.brewersfriend.com/refractometer-calculator/
http://seanterrill.com/2012/01/06/refractometer-calculator/
There are others.

 

[Bottoms_Up]

For instance. Personally, I find it easier to just use a hydrometer for my FG readings. It's not wasteful since I'm going to taste it anyway.

True, but sometimes it's convenient to check the SG during fermentation, for example when starting the Diacetyl rest. At that time, the taste is not as important, and a small sample would be preferable.

 

[Bottoms_Up]

Not just for final gravity readings.
As soon as alcohol is present in your sample, a refractometer correction formula is needed. This due to alcohol having a much lower refractive index than water. The higher the fraction of alcohol in your sample, the larger the difference between the reading and the corrected (accurate) value.

Here are some refractometer correction calculators:
https://www.brewersfriend.com/refractometer-calculator/
http://seanterrill.com/2012/01/06/refractometer-calculator/
There are others.

In the Brewer's Friend calculator, shouldn't the wort correction factor be 1.04 rather than 1.0?

 

[mac_1103]

shouldn't the wort correction factor be 1.04 rather than 1.0?

You can change it to whatever you want. It's actually specific to your own refractometer and each wort, not one size fits all. But I think a lot of people just use an arbitrary 1.04 (or 1.03 or 1.02 or...).

 

[kevin58]

Just get a quality hydrometer and be done with it. You can't beat the ones made by Brewing America:
https://brewingamerica.com/products...es-triple-scale-hydrometer-by-brewing-america

Edited to include the correct link.

 

[IslandLizard]

Just get a quality hydrometer and be done with it. You can't beat the ones made by Brewing America: https://www.amazon.com/Hydrometer-A...hy=107252&hvtargid=pla-4583589133214260&psc=1

Oops... That link sends us to a Proof and Tralle hydrometer, used in distilling to measure the % of alcohol in distillates (and no sugars present)!

Here's a link to the same brand (Brewing America) hydrometer: which is what you'd need to measure sugar content (gravity) in wort/beer:
https://www.amazon.com/dp/B001X27L9...ome-garden&sp_csd=d2lkZ2V0TmFtZT1zcF9kZXRhaWw

Although these are fine instruments, from a good brand, $30 can be a bit of a steep price. But you'll get a jar and cleaning brush with it.

You could probably get a very similar one at your (local) homebrew store for between $10-15 plus ~$5 for a plastic jar that won't break easily when knocked over by accident.

Notes:
If you go the generic route (no fancy brand), look for a hydrometer with an easy to read all-white scale (no color patches on it!) with a scale between 0.990 - 1.100.
A longer physical length of the scale makes reading the values easier. Even only a 1 cm longer physical scale (between 0.990 and 1.100) can make a big difference in the ability to read it. Some cheap ones that tend to come with kits tend to have a shortish scale with color patches, that are not easy to read.

 

[Yooper]

True, but sometimes it's convenient to check the SG during fermentation, for example when starting the Diacetyl rest. At that time, the taste is not as important, and a small sample would be preferable.

Then you could use the correction calculator. Just fill it out appropriately with the OG, current SG and use the ‘with alcohol present’ choice.

For the wort correction factor, that’s easy. Measure your wort with a calibrated hydrometer (checking it is 1.000 with RO water), then check your calibrated refractometer (use RO water and make sure it is 0, and if it’s not, adjust it). I’ve had to redo my refractometer several times as bumping it has changed it.

Then, do the wort correction factor. Repeat several times (more is better) after several batches of beer with cooled wort. Then, do this: https://www.brewersfriend.com/how-to-determine-your-refractometers-wort-correction-factor/

My WCF was not far off from 1.04 but that’s really not much different than 1.0 in the big picture so I just ignore that usually. However, while there is not a huge difference between an OG of 1.048 and 1.046 (what that 1.04 vs 1.0 gives), for higher gravity worts it could be more significant.

 

[kevin58]

Oops... That link sends us to a Proof and Tralle hydrometer, used in distilling to measure the % of alcohol in distillates (and no sugars present)!

Here's a link to the same brand (Brewing America) hydrometer: which is what you'd need to measure sugar content (gravity) in wort/beer:
https://www.amazon.com/dp/B001X27L9...ome-garden&sp_csd=d2lkZ2V0TmFtZT1zcF9kZXRhaWw

Thank you for the correction. True story about the Brewing America hydrometer: I dropped my test sample tube on a concrete garage floor. Shattered tube right? They are made of glass after all. Nope. The glass rim around the bottom on which you stand the tube up with broke and that's all. I was able to cut a piece of thin (1/8") Luan plywood and epoxy it to the bottom as a new base. That was three years ago and it's still rockin'.

 

[Bottoms_Up]

Then you could use the correction calculator. Just fill it out appropriately with the OG, current SG and use the ‘with alcohol present’ choice.

For the wort correction factor, that’s easy. Measure your wort with a calibrated hydrometer (checking it is 1.000 with RO water), then check your calibrated refractometer (use RO water and make sure it is 0, and if it’s not, adjust it). I’ve had to redo my refractometer several times as bumping it has changed it.

Then, do the wort correction factor. Repeat several times (more is better) after several batches of beer with cooled wort. Then, do this: https://www.brewersfriend.com/how-to-determine-your-refractometers-wort-correction-factor/

My WCF was not far off from 1.04 but that’s really not much different than 1.0 in the big picture so I just ignore that usually. However, while there is not a huge difference between an OG of 1.048 and 1.046 (what that 1.04 vs 1.0 gives), for higher gravity worts it could be more significant.

The Brewer's Friend Calculator seems to use an old conversion formula that is not as correct as Sean Terrill's formula. For example, for a Brix of 16.7, Brewer's Friend calculates the S.G. as 1.069. Sean Terrill's formula calculates it as 1.066.

 

[dmtaylor]

Terrill assumes WCF 1.04, Brewer's Friend assumes 1.00. Personally, based on my own data over dozens of batches, I know that the WCF of my refractometer is precisely 0.995. YMMV

Also in comparison, Terrill's calculator is more accurate when SG is less than 1.014, and Brewer's Friend is more accurate above 1.014. This likewise is based on many dozens of hours of data analysis of dozens of batches comparing refractometer to hydrometer.

Based on these conclusions, I typically no longer use my hydrometer, knowing my refractometer is accurate within plus or minus 0.0015 SG average. Now I compare the two instruments maybe a couple times per year just for the extra data.

 

[mac_1103]

For example, for a Brix of 16.7, Brewer's Friend calculates the S.G. as 1.069. Sean Terrill's formula calculates it as 1.066.

Terrill assumes WCF 1.04, Brewer's Friend assumes 1.00.

And if you enter 1.04 into the BF calculator, the result is 1.066. Isn't it nice when things have explanations?

 

[Bottoms_Up]

I just checked the FG of my current beer, at room temperature, and after degassing it. The results:

Tilt: 1.006 (not fully calibrated and read before degassing).
Hydrometer: 1.012
Older Refractometer: 1.025 (BRIX 6.6 with corrections)
Newer Refractometer: 1.026 (BRIX 6.8 with corrections)

The Hydrometer reading seems most reasonable, as it should. The Refractometers - with the corrections - are totally out to Lunch! They might be OK at OG, but IMO are useless (unreliable) at FG. Part of the difference may be because I mashed the beer so that the resultant beer would be a little sweeter than normal. The unfermentable sugars may account for some of the difference, but it's hard to imagine that it would account for all of the difference.

 

[Yooper]

I just checked the FG of my current beer, at room temperature, and after degassing it. The results:

Tilt: 1.006 (not fully calibrated and read before degassing).
Hydrometer: 1.012
Older Refractometer: 1.025 (BRIX 6.6 with corrections)
Newer Refractometer: 1.026 (BRIX 6.8 with corrections)

The Hydrometer reading seems most reasonable, as it should. The Refractometers - with the corrections - are totally out to Lunch! They might be OK at OG, but IMO are useless (unreliable) at FG. Part of the difference may be because I mashed the beer so that the resultant beer would be a little sweeter than normal. The unfermentable sugars may account for some of the difference, but it's hard to imagine that it would account for all of the difference.

What did the two different correction calculators say, though? Of course with alcohol in the mix, you have to do that correction once you take the reading. Since alcohol skews the refraction of light (which is what the refractometer reads, after all), using the correction formula for your WCF is usually pretty spot on.

 

[dmtaylor]

Older Refractometer: 1.025 (BRIX 6.6 with corrections)
Newer Refractometer: 1.026 (BRIX 6.8 with corrections)

This is confusing.... These readings might not be corrected for presence of alcohol. You must use Terrill or BF calculators including the OG as part of the calculation, not just the FG. Unless you're reporting the Brix readings themselves, you might be closer to 1.009, not 1.025. Is the 6.8 Brix the actual reading from the refractometer? Or does your refractometer read in SG in addition to Brix?

 

[Bottoms_Up]

What did the two different correction calculators say, though? Of course with alcohol in the mix, you have to do that correction once you take the reading. Since alcohol skews the refraction of light (which is what the refractometer reads, after all), using the correction formula for your WCF is usually pretty spot on.

The correction is made on the BRIX reading, and accounts for the alcohol and other distortions in the reading. I forgot to include the OG readings, so that would account for the difference (see next post).

 

[Bottoms_Up]

This is confusing.... These readings might not be corrected for presence of alcohol. You must use Terrill or BF calculators including the OG as part of the calculation, not just the FG. Unless you're reporting the Brix readings themselves, you might be closer to 1.009, not 1.025. Is the 6.8 Brix the actual reading from the refractometer? Or does your refractometer read in SG in addition to Brix?

View attachment 880379

You're right. I forgot to include the OG numbers. Thanks for that. With the correction, the FG comes out to 1.0123, exactly the same as the Hydrometer reading (1.012)!

 

[jaspermonroe10]

Yes you should definitely adjust FG readings when using a refractometer, since alcohol affects the reading. I usually use an online calculator to get an accurate result, it makes a big difference compared to a hydrometer.

 

[Kickass]

same as the Hydrometer reading

Alright! We made it friends! Somebody should have said something up around post #2.

 

[Peebee]

Making up?

I can't be having that, so I'll stick my oar in ... that's guaranteed to wind things up again ... I don't know why, but it just does (is it me?).

Refractometers don't have to be adjusted for FG because of any fault of that technology, hydrometers are affected by alcohol too. Not as much, but more importantly because they are what we're used to. Refractometers aren't adjusted to read "correctly" but are adjusted so they "emulate" a hydrometer.

I can't use hydrometers, and refractometers are easier but still dodgy (I can't "fix" my vision quickly, nothing glasses can correct, so "peripheral" vision is the norm) so I must rely on an even older technology (back to basics ... mass/volume). And believe me ... hydrometers come with a whole range of "issues" that must be "fixed". Temperature is the main one. So, hydrometers "emulate" the older technology. Most notably shown by "specific gravity".

"SG" was never created for "hydrometers", they just borrow it. "SG" is a temperature compensation (that'll confuse some). You might see evidence of it on some of the better hydrometers; they'll be marked "60°F/60°F" or "20°C/20°C", or the like. For cheap bits of tat, hydrometers do something remarkable: They can "weight" differences in an "incompressible" medium (liquid) as it compresses and expands. A more valuable use of hydrometer technology is: