10+ Point Difference in Gravity Readings?!

[boondocksaint]

Hi all,

I brewed a pale ale today on my electric HERMS set up. Everything went well but I was a little low on my pre-boil gravity so I decided to stop the sparge at 13 Gal instead of the usual 14 Gal. (I brew 10 Gal batches and try to put ~12 Gal in the conical to account for trub/hop loss, etc.)

Est. OG: 1.064

At the end of the boil I started pulling samples and was getting different readings. I decided to stir and make sure the wort was well mixed and try again. My refractometer was giving me 1.074. My old school hydrometer was giving me 1.062/1.063. I pulled three different samples and made sure they were cooled down: First to ~90 degrees and the next two to <80 degrees. I got the same readings:

-Refractometer 1.074 every time (I re-set it with tap [well] water and dialed it back in to 0 it out -Was not far off).

-Hydrometer 1.062/1.063 every time.

Decided to just roll with it rather than try to adjust. Sanitized everything. Recalibrated my Tilt floating hydrometer and it read 1.000 with plain old water. Pitched the Tilt in to the fermenter and got everything closed up. Checked the Tilt after a few minutes and it read 1.069.

Any of y'all know why there would be such a big gap in readings between the refractometer and hydrometer? Which one, if either can be trusted? I know there is a correction for the refractometer after fermentation but I thought it was an accurate way to measure gravity pre-fermentation. Somehow the Tilt decided to split the difference?

At the end of the day, it will make beer. I get that, but I don't like not knowing why I missed my numbers and why the three different tools to measure gravity were all three different. Plus, one of my goals and the reason I invested in building the electric set up was controllability and repeatability. Whiskey Tango Foxtrot, over...

 

[wepeeler]

I often get different readings between the refractometer and Tilt. I use the refractometer as a guide during the brewing process, and I honestly don't trust the Tilt OG readings very much. I use the Tilt as a guide during fermentation. More to see when fermentation slows for D Rest and whatnot (ie dry hopping). Honestly, I don't use my regular hydrometer anymore, at all. As long as I'm within 2-3 (usually 1-2) points on the refractometer, I roll with it. Once you make a recipe more than a few times, you should be able to be within a few points, for each measuring tool you use. As in, 1-3 points either way on the refractometer from recipe to recipe. Same for the Tilt etc.

 

[mashdar]

If it reads 1.000 in water, the hydrometer is likely very accurate.

What refractometer are you using? I've never used one, but I hear they require a bunch of adjustments.

It sounds like most people use tilts for relative measures, rather than absolute.

 

[boondocksaint]

I often get different readings between the refractometer and Tilt. I use the refractometer as a guide during the brewing process, and I honestly don't trust the Tilt OG readings very much. I use the Tilt as a guide during fermentation. More to see when fermentation slows for D Rest and whatnot (ie dry hopping). Honestly, I don't use my regular hydrometer anymore, at all. As long as I'm within 2-3 (usually 1-2) points on the refractometer, I roll with it. Once you make a recipe more than a few times, you should be able to be within a few points, for each measuring tool you use. As in, 1-3 points either way on the refractometer from recipe to recipe. Same for the Tilt etc.

Thanks. Yeah, I have typically had pretty accurate readings with the refractometer and have just never had such a huge gap in readings previously. Maybe PFM...

 

[day_trippr]

fwiw, I remember a ~10 point difference between refract and hydro with my chocolate stout on a batch years ago. Iirc the refract got it right and the colloidal mix of cocoa powder and wort upset the hydro...

Cheers!

 

[mashdar]

fwiw, I remember a ~10 point difference between refract and hydro with my chocolate stout on a batch years ago. Iirc the refract got it right and the colloidal mix of cocoa powder and wort upset the hydro...

Cheers!

Did hydro measure high? I would think suspended solids would increase density?

edit: i worry about that a lot on OG readings.

edit 2: wrote "wouldn't" instead of "would"

 

[day_trippr]

That's what appeared to be the case...

 

[Bramling Cross]

fwiw, I remember a ~10 point difference between refract and hydro with my chocolate stout on a batch years ago. Iirc the refract got it right and the colloidal mix of cocoa powder and wort upset the hydro...

Cheers!

I agree. Contemporary hydrometers have become really sketchy (even lab-spec--what does that really mean when there's so much Chinese price-point garbage sold at 4x the price masquerading as lab-spec equipment? And how do you tell the difference?). Plus, it's a drag to properly calibrate a hydrometer. Whenever I teach someone to brew, I strongly recommend a hydrometer.

Frankly, I've given up on my hydrometers--and I have some very old, very reliable, very accurate West German hydrometers. Unfortunately, they have enormous sample jars and I'm confident enough in my process that I'd rather have that beer in my keg.

The important thing is that your measurements agree with what your tongue is tasting. I've found that my refractometer is accurate enough for that regarding various mash, pre-boil, boil, and OG measurements. My TILTs are a complete disaster and require constant calibration off of my refractometer--but they're amazing and I wouldn't trade them for the world because they provide the all-important flatline indication that signals the cessation of active fermentation and the need to package.

I'll argue that absolute precision (what the hydrometer is supposed to be good at) is a lot less important than what the tongue perceives. In this respect, I think my tongue is a far better instrument than a hydrometer when judging a yeast's performance and resultant FG. Moreover, my tongue tends to agree with my upstream refractometer readings. Regarding the TILT... it might say 1.014 or 1.006, but that doesn't matter provided the beer tastes the way I intended it to.

What I'm getting at is this: The instruments don't matter, the results do. I've described what works best for me, that may not be the best thing for you. Keep iterating and discover what works best for you.

 

[boondocksaint]

If it reads 1.000 in water, the hydrometer is likely very accurate.

What refractometer are you using? I've never used one, but I hear they require a bunch of adjustments.

It sounds like most people use tilts for relative measures, rather than absolute.

It’s the Brix/Secific Gravity one that Northern Brewer sells for like $49.95

 

[hottpeper13]

I use a wine thief for sampling and the hydrometer floats in it. I will never give that up because of the 2-for I get. 1-A data point and 2- A sensory sample for quality control. What do you guys do for sensory with the refractometer,lick it?

 

[bwible]

Hydrometers are calibrated to different temps. I had one that was calibrated to 68 or something that got broken and the replacement I bought said it was calibrated to 60. If you haven’t already you might want to double check what it says yours is calibrated at on the paper it came with in the tube.

I measure my sample with my thermometer (assuming my thermometer is accurate) and then use this utility for conversion. Been pretty spot on.

https://www.brewersfriend.com/hydrometer-temp/
I never had a refractometer. Never used one. But I understand there is a shade or a line or something you have to read and interpret and its often tricky.

Don’t even get me started on the Tilt.

 

[hotbeer]

As far as hydrometers being calibrated at different temperatures...

Even 15° of temp difference from what a hydrometer is calibrated for will only make 0.001 difference in SG.

For most of us, we're lucky if we have a hydrometer that lets us read to within 0.002 or even less precision with any reliable accuracy.

 

[tracer bullet]

What I've found is that you need to let the wort settle to get a good refractometer reading. Hydrometer readings can have proteins, hop micro bits, etc. in them and still give accurate readings but refractometers don't like that stuff, it affects how they work (refracting light through the sample). Let that wort sit for a little while and you'll get a more accurate reading. One that I bet gets much closer to the hydrometer the longer you let it sit.

 

[MaxStout]

What I've found is that you need to let the wort settle to get a good refractometer reading. Hydrometer readings can have proteins, hop micro bits, etc. in them and still give accurate readings but refractometers don't like that stuff, it affects how they work (refracting light through the sample). Let that wort sit for a little while and you'll get a more accurate reading. One that I bet gets much closer to the hydrometer the longer you let it sit.

My refrac gives wonky readings if the wort sample has any solids floating around. I draw a sample, put it in a small glass and wait for it to cool to 68F. Then draw a bit with an eye dropper, being careful not to get any of the dregs. I get readings that concur to within 1 gravity point with my hydrometer.

Another thing about refracs--I find I have to cal mine with distilled water before every brew. Just sitting in its box, the damn thing can drift 2 or 3 gravity points.

Sensitive instruments are sensitive.

 

[mac_1103]

Even 15° of temp difference from what a hydrometer is calibrated for will only make 0.001 difference in SG.

Well yeah, but the OP might be dealing with a 20 or 30 degree difference.

I pulled three different samples and made sure they were cooled down: First to ~90 degrees and the next two to <80 degrees.

Sensitive instruments are sensitive.

Film at 11.

 

[boondocksaint]

Hydrometers are calibrated to different temps. I had one that was calibrated to 68 or something that got broken and the replacement I bought said it was calibrated to 60. If you haven’t already you might want to double check what it says yours is calibrated at on the paper it came with in the tube.

I have had/been using this hydrometer for the better part of 10 years and have never once looked at the paper that came wit it to see what temp it is calibrated to! Ha! Will have to check that out.

 

[boondocksaint]

What I've found is that you need to let the wort settle to get a good refractometer reading. Hydrometer readings can have proteins, hop micro bits, etc. in them and still give accurate readings but refractometers don't like that stuff, it affects how they work (refracting light through the sample). Let that wort sit for a little while and you'll get a more accurate reading. One that I bet gets much closer to the hydrometer the longer you let it sit.

Never thought of needing to let the wort settle before taking the sample. Makes sense

 

[DBhomebrew]

On the other hand, one must be sure to thoroughly mix the entire volume of wort just before sample collection in order to defeat stratification.

 

[MaxStout]

On the other hand, one must be sure to thoroughly mix the entire volume of wort just before sample collection in order to defeat stratification.

I usually draw a bigger sample than I need, filling the hydrometer jar to the top. Since I usually add a Whirlfloc to the boil, by the time the hydro sample has cooled, the trub settles to the bottom of the jar. Then I decant the sample into another hydro jar, give that a swirl and measure. I also use that same sample for refrac measurement.

 

[tracer bullet]

Regarding methods, I keep a pair of chilled shot glasses nearby. After thoroughly mixing the wort from the mash, I dip one glass in to get about a 2 ounce sample, hold that for maybe 20 seconds to cool some, then pour it into the 2nd shot glass and let it sit a while. This gets it to room temp pretty quickly.

I'm usually trusting that I'm "close enough" and so I go about getting ready for boil, upping the temps, getting hops weighed if I haven't already, etc. Maybe 15 minutes later I'm done with all that and ready to get back to the sample. The contents of the shot glass have settled quite a bit and so I take a refractometer reading with it, and next I take a pH reading. Last step is to take a sip of it and see what the wort tastes like!

 

[mggray87]

Hydrometers are calibrated to different temps. I had one that was calibrated to 68 or something that got broken and the replacement I bought said it was calibrated to 60. If you haven’t already you might want to double check what it says yours is calibrated at on the paper it came with in the tube.

I measure my sample with my thermometer (assuming my thermometer is accurate) and then use this utility for conversion. Been pretty spot on.

https://www.brewersfriend.com/hydrometer-temp/
I never had a refractometer. Never used one. But I understand there is a shade or a line or something you have to read and interpret and its often tricky.

Don’t even get me started on the Tilt.

dam i want the tilt pro but now u make me want to say no LOL