Somone is lying! Hydrometer vs Refractometer, Pro advise needed

Okay, so I got a new refractometer (blue box, model RSG-100ATC) so that I could easily grab PBG and OG. Previously I just used a floating hydro. Here is the deal. I have pure RO/DI water for my fish tank so I calibrated the refractometer with that (per the instructions) and verified its at 0.

To do this side by side verification I actually took a cup of pre-boiled wort and cooled finished wort and then measured them side by side after the brew day (this means the PBG was measured about 3 hours after it was pulled from the kettle if this matters, but was sampled @ 72 degrees)

Hydro readings: PBG: 1.039; OG: 1.050
Ref readings: PBG: 1.048; OG: 1.056

Can I get some pro tips here or at least a lie detector? I am still working out my process and only have 6 all grains under my belt (8 brews total) so any and all advice is 100% welcome.

Thanks brewers!

pretty sure you need to use some sort of brewing software that has a Refracto calibration. you need to use your hydro to calibrate it.

-=Jason=-

How many measurements did you take with the refractometer? You want to take 3 and average them if they are close, or throw out the outlier if they are not. You also want to stir just before taking the refract reading so that you get a well-mixed sample. Finally, it's also important to get a sample that is free from particles (hops, protein, etc) and air bubbles.

You should also be aware that the brix to SG conversion factor isn't exactly 4 (it's very close to it though), and that refractometer readings aren't perfectly accurate since they aren't designed for use in wort. To compensate for that, you need to calculate your correction factor, which is usually between 1.02 and 1.06. A good software or spreadsheet will help you figure all the math out easily and dial it in.

Don't forget that a hydrometer is usually calibrated at 60 degrees, so you have to do a temp calculation on that as well

In your opinions, which would/do you use for measurement. It sounds like hydrometer is the easier/more reliable way to go?

I would also check the hydrometer for calibration, along with doing the temp calc at 60 degrees. My RM says to check with distilled water, don't know if that makes a difference or not. Both should read the same if calibrated correctly.

Remember if you use the RM for final gravity, you have to do another equation to figure out the SG. Download the free spreadsheet from Morebeer to do this easily. I have cross tested this on several batches and it is right on.

bushwilliams said:

In your opinions, which would/do you use for measurement. It sounds like hydrometer is the easier/more reliable way to go?

Click to expand...

When i remember to take readings, I usually use the refract on brew day and hydro after fermentation. I am hoping to convert over to using a refractometer only, but I am still not convinced that it gives me the accuracy I want for post-fermentation readings, even with the new adjustment formulas.

Does your refractometer have automatic temperature adjustment. I assume it does but make sure.

Yeah that one has it. End of the model # ATC = Automatic Temperature Compensation. I just bought the same unit but havent verified it yet against the hydro. Seems kinda strange, they should be lining up and that extra 12 degrees isn't going to amount to much of a hydro correction. Hmmm, now I'm wondering about mine.

I think Hydrometers are more reliable, but you do need to check it at the correct temp. 72 is a little high, but not enough to change the OG six points.

What were the brix readings for the refractometer samples?

-a.

I rarely use my hydrometer at all [heck, I almost never check FG], but today I wanted to check FG on a saison to figure out whether it was done fermenting.

I pulled a sample for the hydrometer tube, and first checked it with my refractometer. I had a brix reading of 7.1, which Beersmith tells me that for an OG of 1.067 calculates out to an FG of 1.004.

I then checked it with the hydrometer, which read in the range of 1.008. Knowing it had come from the (warm) fermenter, I checked the temp, and it was 82 degrees. Using the temperature correction, that gives me a FG value of 1.011.

Obviously there's a problem here.

So I checked the hydrometer in water. 1.003. Measured the temperature; it was also just above 80 degrees. So I had to correct that value as well, which gives me 1.006.

So my refractometer was spot on: it was my hydrometer that was 0.006 points off!

did you calibrate the refractometer? Mine is dead on.

Yes, I did calibrate it according to the instructions. I am going to run a couple more tests with some starter wort @ correct temps and see if I can get to the bottle of this.

There is a difference between temperature correction/callibration and actual calibration. If you take a scale and measure out 9 grams of water and then add to that 1 gram of white sugar ( docent have to be special) mix until all sugar is dissolved then measure with your refract and again with spindle. If they are more
Different than 10.0% than you can adjust the scalemin your refract... It's broke.
Important to remember that any fermented wort will wildly throw off your refractometer readings and any carbonation will wildly throw off hydrometer spindle readings. The difference is that alcohol/refractometer readings cand be compensated for fairly reliably if you make some assumptions about the alc content ( that's what the programs i have used are doing with post-pitch refract readings)

Celticway said:

I would also check the hydrometer for calibration, along with doing the temp calc at 60 degrees. My RM says to check with distilled water, don't know if that makes a difference or not. Both should read the same if calibrated correctly.

Remember if you use the RM for final gravity, you have to do another equation to figure out the SG. Download the free spreadsheet from Morebeer to do this easily. I have cross tested this on several batches and it is right on.

Click to expand...

+1, ALL of my hydrometers are off. Once you check them and know, you can apply that factor to your readings. Also make sure you are at your cal temp.

Just keep taking samples with both the hydrometer and refractometer and comparing the results. Eventually you will get the knack? the understanding? I don't know what it is... but your refractometer will become the main tool you use and the hydrometer will just become a 6 ounce sample of beer to taste. I really don't use the hydrometer till I am ready to keg. I don't have any surprises when I do.

I don't know that I have verified my refractometer against a hydrometer for OG in a long time. That aside there was a podcast on Basic Brewing Radio with Sean Terrill where he found his FG readings to always read lower than they truly were with his refractometer. He verified this with several independent brewers in an experiment, He has created a correction sheet that he claims comes up with a more accurate FG reading. http://seanterrill.com/2011/04/07/refractometer-fg-results/

For what it is worth I was getting FG readings that were unnaturally low on many batches with my refractometer. Since using his spreadsheet my FG readings make a lot more sense to me. You'll have to decide for yourselves. I have not verified the results as my hydrometer is MIA, but the readings with his sheet come much closer to what I am expecting and tasting than the readings did in Beersmith.

Cheers