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4 min read

Tilt Hydrometer Accuracy Testing (Part 1)

Yes, I realized the logo was upside down while taking this

Ever since I began brewing, I’ve been fascinated by electronic specific gravity sensors. Early in my brewing journey, I tried building my own using various technologies, but eventually I discovered the Tilt Hydrometer. The Tilt provided exactly what I was looking for—a real-time window into my beer’s fermentation progress. Because it could show me how the gravity was changing over time, I never worried too much about its absolute accuracy. However, despite the Tilt’s promises of accuracy (even when fermenting under pressure), I’ve always been a bit skeptical.

With the upcoming release of TiltBridge, I needed to develop a new calibration workflow, which turned out to be the perfect opportunity to test how accurate Tilts really are during active fermentation. Over the years, I’ve collected one of each generation of the Tilt Hydrometer (Gen 1, Gen 2, Gen 3, the Tilt Pro, and the Tilt Pro Mini), and my plan is to test them all side by side in the same fermentation.

Equipment and Calibration Phase

This experiment tested most of the generations of Tilt Hydrometer (see note below about Gen 1) in a ferment of a sugar-water mixture using typical brewing yeast. The experiment was divided into two phases: Calibration and Ferment.

Equipment

  • Tilt Hydrometers: Original Tilt generations 2 and 3, Tilt Pro, Tilt Pro Mini
  • 5 lbs Table Sugar
  • Water
  • Anton-Parr DMA 35 Density Meter
  • Spike Flex conical fermenter (with PRV)
  • TiltBridge (connected to Fermentrack)
  • Yeast: Omega Labs Oktoberfest Lager Yeast

Calibration Phase

During the calibration phase measured amounts of sugar and water were blended to create three mixtures which could be used to calibrate the Tilt's specific gravity readings. Pure water was used for the first reading, with two sugar-water mixtures used for additional data points.

Mixture 1 (Pure Water)

Pure water was added to the fermenter alongside the Tilt Hydrometers and allowed to reach room temperature. The specific gravity of the water was then read as was the specific gravity transmitted from each of the Tilts. The water was then drained from the fermenter.

Mixture 2 (2lbs Sugar)

2 lbs of table sugar was added to a pitcher, which was then filled to the 1 gallon mark with warm water and poured into the fermenter. A second gallon of cold water then added to the fermenter. The specific gravity was read from the water at the top of the fermenter, as was the specific gravity transmitted from each of the tilts.

Mixture 3 (3 lbs Sugar)

3 lbs of table sugar was added to a pitcher, which was then filled to the 1 gallon mark with warm water and poured into the fermenter (which already contained Mixture 2). The specific gravity was read from the water at the top of the fermenter, as was the specific gravity transmitted from each of the tilts.

Calibration Results

As expected, the specific gravity readings of each Tilt were reasonably in line with the measured gravity from the DMA 35:

Initial Calibration Data

This is good news, as it means that - in line with Tilt's claim - no calibration is required out of the box.

Next: Ferment Phase and Part 2

I performed the Calibration Phase last night, and ended the evening by adding the yeast to the sugar-water mixture. No activity has been seen as of now (roughly 14 hours in) but I do have a few observations so far which I think it's important to note:

Graph of the Yellow Tilt Pro (Gravity in red)

First, interestingly, the gravity has appeared to climb over the past 14 hours. There's a few reasons I can think this might have happened:

  • There was sugar in the Omega Yeast pack
  • The water density rose at the temperature dropped, and the Tilt is not accounting for this
  • I didn't blend the water-sugar mixture well as I added it to the existing mixture in the fermenter

...except the gravity didn't actually rise:

Assuming the yeast kicks in here soon, this has the promise to be a very interesting experiment!

Last Note: About the First Gen Tilt

As an owner of a first generation Tilt, I had originally intended to include this in the comparison as well. Unfortunately, prior to the start of the experiment I had to change the battery on the Tilt and realized during the Mixture 1 test that the seal was no longer water tight. I dried out the inside, added a new battery, and tried again – but water again was able to get inside.

I bought this tilt back in 2016, and my guess is that over the past eight years the seals have dried out. Since I use this Tilt to test TiltBridge I didn't want to risk any further damage over the course of the test, and decided to pull it out. For what it's worth: the Gen 1 Tilt registered 1.000 in plain water - in line with the others.