Learn from past batches and keep your records¶
Comparing fermentation curves¶
The Compare page lets you overlay fermentation curves from up to five batches on a single chart so you can spot differences at a glance.
Selecting batches¶
Open the Compare page from the navigation menu. Every active and completed batch appears as a selectable badge. Tap a badge to add that batch to the chart; tap it again to remove it. You can select up to five batches at a time. If you need to swap one out, deselect it first to free a slot.
How the chart works¶
Each batch starts its curve at hour zero, regardless of when fermentation actually began. The system takes every reading for a batch, sorts them by timestamp, and measures the elapsed hours from the first reading. This normalization lets you compare a batch that started in September against one from January on the same horizontal axis.
The vertical axis shows specific gravity (SG). Each batch gets its own colour so you can trace individual curves through the overlay.
Archived batches¶
Archived batches do not appear on the Compare page. The batch list excludes them by default to keep the selector manageable.
If you need to compare against an archived batch, open that batch's detail page and change its status back to completed (unarchive it). It will then appear in the comparison selector. You can re-archive it when you are done.
Understanding the comparison stats¶
Below the chart, a table summarizes key metrics for each selected batch. Here is what each row means and why it matters.
OG (original gravity)¶
The first gravity reading recorded for the batch. In winemaking, OG reflects the sugar concentration of your must and determines the potential alcohol of the finished wine. Comparing OG across batches tells you whether starting sugar levels were consistent from year to year.
Current SG (specific gravity)¶
The most recent gravity reading. During active fermentation this number drops as yeast converts sugar to alcohol. For completed batches it represents the final gravity.
Estimated ABV¶
Alcohol by volume, calculated as (OG - SG) x 131.25. This provides a quick estimate for wines fermenting to dryness. The result may differ slightly from a lab analysis, but it is reliable for day-to-day monitoring.
Attenuation¶
The percentage of available sugar that has been consumed, calculated as (OG - SG) / (OG - 1.000) x 100. An attenuation near 100% means the wine fermented to dryness. Lower values can indicate residual sugar, which may be intentional (off-dry style) or a sign of a stuck fermentation.
Gravity change (48-hour)¶
The rate at which gravity dropped over the most recent 48-hour window, shown in points per day. A negative value means gravity dropped (normal during active fermentation). A value near zero on a batch that has not reached dryness can signal a stall.
Days fermenting¶
The number of days since the batch's start date. Comparing this across batches helps you calibrate expectations: if last year's Riesling took 14 days and this year's has been going for 21, that warrants investigation.
Estimated days to dry¶
A projection based on the current 48-hour velocity and a target gravity of 0.996. The system divides the remaining gravity points by the current daily drop rate. If velocity has slowed or the batch has already reached the target, this column shows a dash instead.
Temperature range¶
The minimum and maximum temperatures recorded across all readings for the batch, in degrees Celsius. Comparing temperature ranges helps you assess whether fermentation environment differed between batches, which can explain differences in fermentation speed or flavour profile.
Readings¶
The total number of gravity readings collected for the batch. A batch with very few readings may have less reliable velocity and projection values.
Getting your data out¶
Each batch detail page has a Download CSV button. Tap it to get up to two spreadsheet-ready files — one for readings and one for activities.
Readings file¶
The readings file is named {batch-name}-readings.csv and contains one row per
gravity reading, sorted oldest to newest.
| Column | Description |
|---|---|
| Timestamp | UTC date and time of the reading |
| Gravity | Specific gravity value |
| Temperature_C | Temperature in Celsius (blank if not recorded) |
| Source | Where the reading came from (for example, tilt or manual) |
Activities file¶
The activities file is named {batch-name}-activities.csv and contains one row
per logged activity, sorted oldest to newest.
| Column | Description |
|---|---|
| Timestamp | UTC date and time the activity was recorded |
| Stage | Fermentation stage when the activity occurred |
| Type | Activity type (for example, addition, note, or measurement) |
| Title | Short description of the activity |
| Details | Additional structured data as JSON (blank if none) |
File format¶
Both files use standard comma-separated values with a header row. Fields that contain commas, quotes, or line breaks are enclosed in double quotes. The files open directly in Excel, Google Sheets, Numbers, or any spreadsheet application.
When to use comparison¶
Vintage review. After bottling, compare this year's batch against the same wine from previous years. Overlaying the curves reveals whether fermentation followed a similar trajectory or diverged. Differences in OG, velocity, or days to dry can prompt you to revisit your process notes.
Troubleshooting a slow fermentation. If a batch seems sluggish, select it alongside a batch of the same variety that fermented normally. The overlay makes it easy to see where the curves diverge. Check the temperature range and velocity columns for clues: a cooler fermentation environment or a steep velocity drop often explains the difference.
Comparing varieties or treatments. If you split a lot into two fermenters with different yeast strains or nutrient regimens, the comparison chart shows the effect side by side.
When to use export¶
Record-keeping. Download your readings and activity logs at the end of each batch to keep an offline archive. The CSV files serve as a permanent record that does not depend on the application.
Sharing data. If you want to discuss a fermentation curve with another winemaker or a supplier, the CSV gives them the raw numbers. They can chart it in a spreadsheet without needing access to your account.
Further analysis. Import the CSV into a spreadsheet or statistics tool to run calculations that go beyond what the dashboard provides, such as plotting gravity against temperature or computing custom velocity windows.