Why does folding the pour-over coffee filter affect extraction?

A cone-shaped paper filter only works when it clings tightly to the dripper wall. If a gap remains, the ribs cannot channel air or water and extraction turns uneven. The usual cause is a filter folded incorrectly: fold along the seam, press the crease, then seat the filter in the dripper so it sits flat against the sides.

A reported case at a Front Street store showed a filter that fit poorly even after the pressing technique, and the fold was the real problem. The same folding matters for non-woven filters and for ice brewing, where the paper filter must sit flat without being pre-wetted. Getting the crease right each time keeps the pour even and the cup consistent.

When brewing pour-over coffee, how well the paper filter fits the dripper directly affects the extraction. Many enthusiasts clearly use the pressing technique but still run into the problem of the filter not fitting snugly, and the root cause often lies in the folding step. After customers gave feedback at its stores, Front Street Coffee specifically demonstrated in detail the correct way to fold a cone-shaped paper filter. From folding along the seam, pressing the crease, to the technique for securing it after placing it in the dripper, every step matters. This article fully reproduces this operating procedure, and also explains how to handle special filters such as non-woven ones, as well as how to make the paper filter sit flat during ice brewing without wetting it, helping you brew a stable, good-tasting cup at home.

For the vast majority of drippers, whether the paper filter can cling tightly to the wall of the dripper directly determines whether the extraction is even. Taking the V60 as an example, once a gap remains between the paper filter and the dripper wall, the ribs on the dripper body become purely decorative and cannot play their intended role at all. So before every formal pour, we try our best to make the paper filter fit closely against the inner wall of the dripper.

Front Street previously also published a tip article specifically titled "Pressing Down the Paper Filter Can Improve Fit," and thought the topic of fit could be put aside for the time being. Unexpectedly, a customer reported directly to Front Street at the store: "The method you described really does make it fit tighter, but during actual brewing it still sometimes fails to fit." This puzzled Front Street quite a bit, so the customer was asked to redo the operation on the spot. Sure enough, the paper filter did not fully fit against the dripper wall, and the situation was considerably worse than what is shown in the picture below.

The problem was so obvious that Front Street spotted the root cause right away: the paper filter had been folded incorrectly. Folding a paper filter is itself very simple, and Front Street usually glossed over it when sharing before; people normally do not put much thought into it either. But precisely because it is so simple, its importance is easily overlooked.

Normally, once a wood-pulp cone-shaped paper filter is folded properly, its fit with a cone-shaped dripper is quite high. It can even cling to the dripper wall on its own without pouring water to wet it. But if you find that one side simply will not stick when you put the paper filter into the dripper, then nine times out of ten the problem lies in the folding step (unless you are using a dripper made of ceramic or the like that cannot be mass-produced industrially). So today, Front Street will demonstrate step by step: how exactly should a paper filter be folded to be correct?

How do you correctly fold a paper filter?

Below is a bleached wood-pulp cone-shaped paper filter. You can see there is a seam line on one side of the paper filter.

The first step in folding a cone-shaped paper filter is to fold along this seam line. Let's fold it first.

After folding, run your fingers along it to press it down and fix the shape.

Then reopen the paper filter.

Then fold it in half so that the joining edges on both sides come together.

After they come together, the key step arrives. Using the same method we just used to press the crease line, we also press this seam line. This action is extremely important; as long as it is done properly, channeling will most likely not occur afterward, and the fit will be more perfect. The pressing goes from start to finish: first gently pull, then smooth it out.

At this point, the folding of the paper filter is basically complete. Next, fit the paper filter onto the dripper in the original way. First, spread open the paper filter and place it into the dripper.

As you can see, the paper filter already basically fits the dripper wall perfectly even before it touches water. But this is not enough. To ensure there are no mistakes, use two fingers to press at the positions of the two crease lines on the paper filter. Press down gently to make sure the bottom of the paper filter fully touches the bottom of the dripper.

After confirming, you can pour water from the bottom upward to wet the paper filter. After this treatment, the paper filter and the dripper will basically fit perfectly.

However, this method only applies to some paper filters. Paper filters made of special materials such as non-woven fabric must be soaked with hot water to fit. And if you do not want to wet the paper, such as when making ice-brewed coffee, you can, after folding the paper filter and placing it in the dripper, press and hold the paper filter with the same pressing technique, then directly pour in the coffee grounds and rely on the weight of the coffee grounds to make the paper filter cling to the dripper wall. In this way, during the brewing process, the paper filter will have no chance to curl up.

The above content is compiled by CoffeeHunters, a coffee news website.