What is the barista origin of rinsing a pour-over filter?

Rinsing the paper filter before brewing is not mandatory, and both wet and dry filters can produce good pour-over coffee. Wetting helps in three ways: it rinses away papery or absorbed odors, preheats the dripper and carafe, and helps the paper sit snugly against the dripper walls.

Skipping the rinse has its own advantages, since a dry filter can hinder blooming and degassing, cause premature extraction of coffee grounds, and absorb some of the brew water. Baristas at Front Street Coffee demonstrated both approaches side by side, pouring iced and hot pour-over, and the choice depends on the beans, the setup and the storage conditions of the filter paper.

In the daily routine of pour-over coffee, some people habitually rinse the paper filter with hot water before brewing, while others place a dry filter directly into the dripper and start pouring. Both approaches have their own rationale—there's no absolute right or wrong. When the baristas at Front Street Coffee were making iced pour-over and hot pour-over at the same time, a customer once asked them about this very question. What practical effects does wetting the filter paper actually bring? And what impact does skipping this step have on extraction? This article will examine three angles—removing papery taste, preheating equipment, and helping the filter fit the dripper—while also analyzing the potential issues caused by wetting the filter, such as hindered blooming and degassing, premature extraction of coffee grounds, and water absorption by the filter itself, to help you make a more suitable choice in different brewing scenarios.

One day, a barista at Front Street Coffee was making iced pour-over and hot pour-over separately, when a curious customer asked: "Why did you wet the filter paper for one, but use a dry filter directly for the other?"

So, is wetting the filter paper really a mandatory step before brewing? If the answer is no, then in what situations is it truly necessary? Below, Front Street breaks down the reasoning in detail.

First, let's talk about the benefits of wetting the filter paper:

1. Rinsing the filter to remove off-flavors

Some friends might think 🤔️—aren't there already filter papers on the market that are bleached with bioactive enzymes and have almost no pulp odor? As long as you choose a reputable brand, you shouldn't need to worry about this issue, right?

However, there's one detail that's easy to overlook—where do you usually store your filter paper? What's the surrounding environment like? Front Street has encountered situations like this: a friend habitually left his filter paper open on a shelf, and since he was a heavy smoker who often smoked alone at home, you can imagine what smells the filter paper ended up absorbing.

As the saying goes, "Success comes from odorless filter paper, and failure comes from odorless filter paper"—filter paper that has no scent of its own is actually more likely to absorb surrounding odors. Of course, if you always keep your filter paper sealed and stored separately, this concern can be eliminated.

2. Preheating the dripper and server

Whether this step is necessary depends on the material of your dripper. If you're using a resin dripper, it doesn't absorb much heat and has limited insulation, so whether you preheat it or not won't significantly affect the final brewing result. But if you're using a ceramic dripper, taking the opportunity to warm it up while wetting the filter paper becomes quite important. (For those who want to learn more about the heat retention performance of different dripper materials, click here.)

Preheating the server in advance ensures that the coffee liquid doesn't lose too much temperature after extraction is complete, allowing you to better appreciate the flavor layers of the coffee.

3. Helping the filter paper fit the dripper better

If you're not confident in your filter-folding technique, you can press down on the filter with one hand while pouring water to wet it—this helps the filter adhere more tightly to the dripper wall. Of course, if your technique isn't up to par, or the filter size doesn't match the dripper, even wetting it may not achieve a proper fit.

If you're aiming for a more even extraction and want to minimize interference from the filter paper, then the following three details about filter paper are worth carefully weighing.

1. Blooming and degassing will be affected.

When the filter paper gets wet, it softens and clings tightly to the inner wall of the dripper. The dripper's original flow channels become covered by the filter paper and can no longer create gaps, so the degassing effect during the blooming stage is compromised.

2. After the filter paper is wet, adding coffee grounds may trigger premature extraction.

"Extraction" begins the moment coffee grounds contact water. If you wet the filter paper first and then add dry coffee grounds, the grounds near the filter paper will be moistened by the residual water—wouldn't that mean some of the coffee grounds enter the extraction state prematurely?

3. The filter paper's own water absorption.

A single filter paper can absorb about 8g of water. If it's already fully saturated, the subsequently brewed coffee liquid won't permeate upward into it. Therefore, after wetting the filter paper and then brewing, the filter typically remains close to white. Conversely, if you use a dry filter, the coffee liquid will seep into the filter fibers—this phenomenon is especially noticeable when brewing dark-roasted beans, and you can see the coffee-colored liquid creeping upward bit by bit.

Going back to the question the customer raised at the beginning, now you should understand why Front Street handles the filter paper differently when making hot brew versus iced brew, right?

- END - Front Street Coffee

No. 10 Baoqian Street, Yandun Road, Dongshankou, Yuexiu District, Guangzhou, Guangdong Province

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