Brewing your own beer can be very rewarding. In the first place because of the product, you create, but what might matter just as much: for the skill, knowledge, and creativity you put into it. The process starts by selecting ingredients and heating them in a controlled manner to extract all the sugars (mashing). After cooling down, fermentation begins by adding yeast. When fermentation has finished, you can add hops (dry hopping) or other ingredients to further develop the flavor. Finally, you bottle your brew and wait for it to reach its final form (lagering). Along the way, there’s a lot of cleaning and monitoring involved, to ensure that your beer shines the way you intended it.

Measuring sugar concentration is a key indicator of how your fermentation is progressing. During fermentation, sugars are primarily converted into alcohol and CO₂. Th CO₂ escapes from the liquid and causes the density to decrease. By tracking the sugar concentration, you can see how far along the fermentation is. It’s hard to determine sugar concentration accurately because of all the other components in the wort. Instead, the density of the wort/beer can be measured, as this is mainly influenced by the changes in sugar concentration. Brewers often use the term “Specific Gravity” (SG), which is the density of the wort compared to the density of water. Alternatively, the wort can be measured optically; the refractive index changes as the sugar concentration changes. This measurement is often expressed in degrees Brix (°Br) or degrees Plato (°P). Although measurement principles are not the same, SG can be converted to °Br or °P and vice versa to give the brewer an indication of how fermentation is progressing. There are additional measurands used for tracking fermentation and on our My Brewbrain platform, you can choose your preferred display unit. So wherever you read SG in this blog, you can substitute it with your preferred measurand.

What does a typical fermentation curve look like?

The image above is from an actual brew from the My Brewbrain platform. This brew was based on a recipe for a Weizen beer. My Brewbrain shows real-time fermentation data as gathered by your digital hydrometer.

Let’s first go through the phases of a typical beer fermentation. I’ve laid them out on top of the graph to help visualize them:

• I Lag phase (0-24 hours): yeast is pitched into the wort. The yeast slowly starts adapting to its surroundings. After that the yeast starts multiplying to reach a high enough population to begin converting sugars. In this phase sugars are only consumed in small amounts and so only a small change in specific gravity can be observed.
• Primary fermentation (1-7 days):
  • IIa Start: The yeast is getting it on and eating all that sugar. The SG will drop with increasing speed. Krausen is formed and your airlock will become very active.
  • IIb End: Tough luck for the yeast’s sweet tooth; the sugars are being decimated and converting the last ones takes more effort. You will see the SG drop with decreasing speed, and finally come to a standstill as there are hardly any sugars left to convert.
• Secondary fermentation (1-2 weeks):
  • III Most sugars are converted, but the yeast has other work to do! It will convert other nutrients into flavors that give your beer character. Specific gravity usually remains constant in this phase.

How does the fermentation curve help me?

Ideally, everything goes well with your brew. You’ve checked regularly and went to bed comfortably, knowing your beer is going to end up just fine! In this case you can use the fermentation graph from your brew as a reference for the next time you make a (similar) brew. If you use an off-the-shelf ingredient kit or a recipe made by someone else, you will likely be advised what starting SG and final SG to look for. Check the start and final specific gravity and compare them to what you expect from your fermentation. If all is well, you can follow the next step in your recipe’s instructions (dry hopping, bottling etc.).

But if something goes wrong during fermentation, you want to act quickly. Here are some examples of issues that you can detect during primary fermentation, when using a Float Pro. The examples won’t cover everything, but hopefully they will help you interpret the data in your graph.

How can I see if fermentation has started?

Specific gravity should start dropping after 1-2 days. If this is not the case, you might still be able to save your brew. Typical causes and actions:

• Temperature too low or too high; check the advised yeast temperature and cool/heat to the target temperature
• Under-pitched yeast or old/unhealthy yeast; add the yeast nutrient or pitch additional active yeast.
• Poor oxygenation: your yeast needs more oxygen, gently shake the fermenter and get the yeast back in suspension

Has fermentation stopped early?

The specific gravity seems to stabilize well above the expected final value. Typical causes and actions:

• Temperature issue; if the temperature went too far off the target, the yeast might have issues performing. Check temperature and cool/heat to correct this.
• Yeast flocculated early; yeast clumps together and so it has less exposed area to the nutrients in the wort/beer. Gently rouse the fermenter or stir with a cleaned tool to resuspend the yeast. Consider increasing the heat slightly to increase activity.

Is my brew fermenting too fast?

Hold your horses! The specific gravity is going down way too fast. This is likely accompanied by a strong temperature rise. Typical causes and actions:

• High temperature; at higher temperatures, the yeast works faster. Cooling the fermentation slightly can reduce fermentation speed
• Overpitching yeast; because there was too much yeast in the lag phase, converting sugars started early. Cooling the fermentation slightly can reduce fermentation speed

Check your brew often

Every brew is different. Even when using the same ingredients and amounts thereof, there are other factors that will influence the process. If you check the graphs on My Brewbrain often, you will start noticing subtle differences between each brew. The Float Pro digital hydrometer is your visual aid during fermentation.

Get started with automatic measurements of your fermentation!

How to learn faster by sharing your fermentation data?

Track your fermentation with the free My Brewbrain platform. You can even share your brews with your friends. Compare brews and learn from each other! We brewers love to share our knowledge.

This post should give you an idea of how you can look at your fermentation graph. Keep checking our blog as we will write more about what you can learn from your fermentation data.

We love to stay in contact with our brewers so feel free to comment on this blog. Or reach out to us via email at support@brewbrain.nl. We’re there to provide support and are always welcoming your ideas on what to improve next.

Have fun fermenting!

Cheers🍻

Eric Stricker
(Founder/Engineer)

Our journey that became Brewbrain with its digital hydrometers, started in 2017, in the evenings after work. We wanted to combine our love for measuring and creating sensors with brewing beer. I personally love how nature and technology can contrast with each other and at the same time work together in harmony. Brewing is a creative process and, just like making music, you must feel the result you are creating. With that in mind, we set out to improve the brewing process by making products that give more control and insight into what you are doing.

The step towards Float Pro

The Float digital hydrometer was released in 2020 and we have learnt a lot from our brewers. And so the time was right to create a new version that performs even better and is usable by the pros. Being the nerds that we are, we poured our heart and soul into the design. We wanted to pack wireless charging in there and make the design as smooth as a good beer going down your throat. We felt that when using a digital device with no screen, you need more feedback on what’s going on, so we included a neat multi-color lid that lets the Float tell you if everything is going like it should. We had developed a custom simulation that models at which angle the device Floats, so that we could optimize the weight and center of gravity to get more accurate readings. The housing is sealed by a seamless ring that stays in place due to its unique design. No hassle when (un)tightening the lid and you can trust the seal to do its job when fermenting under pressure.

Interested in our Float Pro, the best digital hydrometer?

So, what’s next?

There’s so much more I would like to tell you about the development of this digital hydrometer, so I will, in the upcoming blog posts. Follow our blog for deep dives into all the aspects of the design. We will also be telling you how to get the most out of your Float Pro and we will announce all the updates that we will be giving for the device and our online platform my.brewbrain.nl.

We love to stay in contact with our brewers so feel free to comment on this blog. Or reach out to us via support@brewbrain.nl. We’re there for support and are always welcoming your ideas on what to improve next.

Last but not least: The best wishes for 2026🎉. Make this an awesome year and your beers even better!🍻

Cheers🍻

Eric Stricker
(Co-owner)

You’ve been using the first Float for quite some time now and you know exactly how to use it to get the best out of your fermentation. But there’s always room for improvement.

We’ve learned a lot from the Float, we’ve used your feedback to create the Float Pro! We’ve optimized for ease of use, so you can brew like a PRO.

Is setting up Float Pro really that easy?

We want your upgrade to be worthwhile, and if the Float Pro doesn’t deliver clear value within 30 days, you can return the product and get your money back.

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