A question for the forum. I use a Tilt hydrometer to monitor my fermentations and I have found that the readings differ from my floating hydrometer and refractometer readings, sometimes wildly. My thoughts are, that even if the tilt is wrong, the OG and FG readings from it are still valid for ABV calculations. Thoughts?
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Maybe the OG, but I wouldn’t trust the FG. They’re great for showing trends, not so much for absolute readings.
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Got a few things going on here:
- Tilts (and the other floating hydrometers) are great for relative tracking purposes, but they’re hard to trust for your final number because of how they can get gunked up by various aspects of fermentation (trapped gasses, yeast coats, etc)
- Refractometers give readings skewed high when alcohol is present. I still use them with a calculator (just remember your OG!) to be “good enough” because I’m not trying to be super precise
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Many instruments are only as accurate as the time spent checking calibration. Tilts will read accurately when there’s no gunk adhered and when properly calibrated. Don’t expect a factory-calibrated Tilt to read accurately – maybe it will, but only with additional comparisons with a traditional hydrometer will you find out for sure.
And as for refractometers… I have spent many dozens of hours learning how to interpret results accurately. When done right, the conversion calculators are good within 0.001-0.002 specific gravity unit. But… well… The main key is to use the right conversion calculator. I find that below 1.014, Sean Terrill’s calculator is more accurate, and above 1.014 then I find that Petr Novotny’s calculations (which is what Brewers Friend uses) are more accurate. A good summation of my experience can be found below, and there are links to a couple more rabbit holes within. If you really want to use a refractometer, you can – HOWEVER… yeah…
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My experience is largely the same.
I like my Tilts for tracking fermentation progress and determining when I’ve hit FG without pulling a bunch of samples. I do small batch brewing — so even just a handful of, say, 4-oz samples eats into my final volume for packaging.
And their FG is accurate enough for my purposes — the ATF isn’t going to fine me if my ABV calculation is off a bit.
But if you really, really want to know FG precisely, you’ll probably want to verify with another instrument.
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The last couple of brews my factory-calibrated Tilt had FGs and OGs ±0.002 compared to my refractometer (using different formulas). Considering that this is their stated accuracy, I think it isn’t that bad. During the fermentation itself it is quite off but that usually settles down as fermentation slows.
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Thanks all. What I was wondering is if it is off by X amount on the OG, wouldn’t it be off the same amount for the FG? And if it off by the same amount, you would still be able to calculate ABV.
That’s how I use ’em.
Considering that they recommend a multi-point calibration, I wouldn’t be confident that the error is constant across the range. Otherwise a single-point calibration should be sufficient.
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I have to calibrate the Tilt at 4 different points across a broad range for it to accurately interpolate. YMMV
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As I am a lazy brewer, I check my Tilt’s calibration only every once in a while. And because my beers are mostly for me, I don’t care how precise the Tilt is. Worrying about the precision of my instruments is not worth my time. But more power to you if it is.
I periodically calibrate my Tilt across three data points per the mfr YouTube instruction. Then, I zero it out in water and check OG with a hydrometer inputting a ‘known’ gravity in the app on brewday.
Still, I only use it to track progress so I know when to increase the temp by a few degrees about 5-10 points prior to anticipated flatline. I then use the length of time it takes from OG to flatline to rest at the increased temp allowing the yeast a chance to clean up any byproducts. (HtB table 6.2)
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So…you may think that this is overkill, but is use a Tilt, EasyDens, and SmartRef and record numbers throughout my brew days on all these devices. I notice that my Tilt, SmartRef, and, EasyDens usually align on the OG and I am confident on the Tilt readings for the OG. I do use the tilt as a compass to make sure that things are proceeding in the right direction throughout the fermentation. However, as the fermentation nears the end, I can’t really rely on the exact readings from the tilt, but it is a good barometer to understand when things draw to a close. This is because as krausen increases and if you dry hop, all those particles/bubbles/etc in the beer can effect the the Tilt’s angle in the beer. For FG or ABV I rely on the SmartRef and EasyDens. To sum things up…I believe in the Tilt’s OG, but would use some other instrument for FG.
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Ive found my tilt to be spot on on most of my beers that are in the low to mid abv. When i start above 1.055 it strays the farther up in gravity I go and diverges from floating hydrometers. It then struggles with FG in higher gravity beers and typically overestimates. I just use it as a trend line and sample for more accurate readings.
I use a Smartref and take readings every so offten during the ferment. I got fed up with inaccurate Tilt readings and sprung for the SR. It is expensive, but saves a lot of grief. I have NOT ponied up for the Easydens yet.
I think the underlying question is: is the Tilt worth it?
Everyone has to decide for themselves. I believe it is because of the trend-line data used for decisions made during the fermentation.
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I think the real purpose of the Tilt is to give you some peace of mind. Many brewers look at airlock activity but, as we know, there’s more to it than that - and the Tilt tells you what’s actually happening. I like how they graph data points, but ultimately it won’t make your beer any better.
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I usually break my tilts out for things like my saisons and anything long aged just so I can have some piece of mind that everything is still moving. 
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So in a nutshell if for example your tilt is reading 1015 FG probably actually 1019?
If there is dried krausen on the top it will make it lean more and give a higher reading than is correct. The amount of krausen can vary, so the accuracy will also vary.