Wort filtration generally happens in two stages. In the first stage, brewers use the spent grain bed as a filter layer and separate the wort from the mash. Brewers call this portion first wort, or first runnings. In the second stage, they wash the remaining soluble extract out of the spent grain with hot water, and the wort obtained is called second wort, or sparging wort. Understanding the first stage is essential because it sets the foundation for wort clarity and brewhouse efficiency.
What Is First Wort?
First wort is the wort separated from the mash before sparging begins. At this point, the spent grain bed acts as a natural filter, trapping solids while clear wort passes through. Because first wort contains the highest concentration of extract, its quality directly affects the final wort gravity, clarity, and flavor. In short, this step is not just a separation stage; it is the first real quality checkpoint in the brewhouse.
Operating Points Step by Step
1. Fill the bottom space with hot water. Pump hot water at 76–78°C into the bottom of the lauter tun until the space between the filter plate and the tank bottom fills with water, just covering the filter plate. This step expels air from the bottom space and prevents air pockets from disturbing the grain bed.
2. Pump in the mash and stir evenly. Pump the mash into the lauter tun and start the raking machine at an appropriate speed to stir the mash evenly. Uniform distribution helps the spent grain settle into an even filter bed.
3. Let the grain bed settle. Rest for 15–20 minutes so the spent grain settles onto the filter plate and forms a filtration layer. A well-formed bed is the basis for clear wort and stable flow.
4. Recirculate until the wort runs clear. Start filtration by alternately opening and closing the wort valve or central filter pipe. Discharge the turbid wort and pump it back into the lauter tun for re-filtration until the wort runs clear. Recirculation usually takes 5–10 minutes.
5. Open the filter cocks and start filtration. Open the filtration cocks in sequence and control the wort outflow rate to begin formal filtration. A steady, controlled flow protects the grain bed from compacting too early.
6. Loosen the bed when flow drops. After about half of the total first wort time, the filter bed compacts, resistance rises, and outflow speed drops noticeably. At this point, close the filtration cocks and run the raking machine slowly to loosen the bed.
7. Restart filtration and stop at the right moment. Restart filtration and pump the turbid wort at the start back into the lauter tun until it runs clear again. Continue filtration until the wort just exposes the spent grain, then stop. At this point, the first stage is complete.
Why This Stage Matters
This stage matters because it determines how much clear, high-gravity wort reaches the kettle. If the grain bed forms poorly or flow is uncontrolled, wort clarity drops, more turbid wort recirculates, and filtration time stretches longer. In short, good separation protects wort quality and keeps the brewhouse running on schedule.
First wort is the wort separated before sparging, and second wort is the wort recovered during sparging. To run this stage well, brewers should fill the bottom space with hot water, distribute the mash evenly, let the bed settle, recirculate until clear, control outflow speed, loosen the bed when flow drops, and stop filtration just as the grain is exposed. When operators follow these points, separation becomes faster, clearer, and more consistent.
