벨카 – Belka

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The real brewing dynamics that a recipe can’t capture

Recipes tell you what to do, but they don’t show what actually happens during extraction.
PORTAL is a concentration (EC)-based coffee brew profiler for espresso and pour-over. It helps you see when and how coffee is extracted in real time, so you can compare brews, improve consistency, and learn faster.

View EC Log Guide

On brewing server or espresso cup.

The first model by Belka, the Belkafilter, was designed exclusively for espresso. However, PORTAL features a sleek funnel shape that can simply be placed over a coffee cup or server to let coffee pass through. It measures espresso, pour-over, even automatic, or capsule coffee.

Different brews, different logs

The x-axis represents time, while the y-axis shows concentration (blue) and temperature (yellow).
These are two overlapping logs from consecutive pour-over brews. The closer the light and dark lines are to each other, the more consistent the brews are. Larger gaps between the lines usually indicate lower consistency.

From our experience with many users and testers, we have repeatedly observed that brewing skill often appears clearly in the logs. When two logs matched closely, the taste was usually very consistent too. When the logs varied significantly, the taste difference was often clear as well.

Real-time brew concentration & temp.

As coffee flows through PORTAL’s funnel, the sensor measures EC (electrical conductivity) and temperature in real time. The data is displayed instantly as a brewing log.
PORTAL uses EC to estimate concentration. In general, liquids with more dissolved substances conduct electricity better. While EC is not the same as TDS, it maintains a consistent relationship in most coffees, so the EC log closely reflects the overall concentration pattern during brewing. Unlike refractometers, EC can also measure flowing coffee in real time.
Temperature is measured with a fast and highly accurate RTD sensor.

Accuracy

Blue line: Real-time EC from PORTAL
Red circles: EC measured with an industrial EC meter
Green X: TDS measured with a refractometer

During a pour-over brew, we collected coffee samples at specific moments and compared PORTAL’s real-time EC data with measurements from an industrial EC meter and a TDS refractometer.

In Chart 1, PORTAL’s real-time EC closely matches the actual EC measurements, even though EC and TDS are not the same values.

To compare their overall patterns, we applied one consistent scale and offset to all TDS values. As shown in Chart 2, the EC and TDS curves follow very similar trends.

Battery

It charges via a USB-C port.
The battery fully charges in 3 hours, and when recording brew logs continuously, it can log around 100 pour-over coffee brews.
Portal will standby for about a week or more in sleep mode.

Cleaning

The funnel and sensor cover can be detached, allowing you to clean them separately from the body.
The PORTAL body is water-resistant, so it can be washed under running water. As long as you avoid harsh scrubbing, using soap is perfectly fine.
The charging connector is waterproof, but you should still be careful to prevent water from entering. If water has entered, you can plug in the charging port after wiping off any moisture.