Why Wet the Filter Paper for Pour-Over Coffee? What Is the Purpose of Pre-Wetting the Filter Paper?

One day, when FrontStreet Coffee's baristas were separately brewing a pot of iced pour-over and hot pour-over coffee, a customer asked: "Why did one of you wet the filter paper while the other started brewing directly without wetting it?"

Is wetting the filter paper a necessary step before brewing? If not, when exactly do you need to wet the filter paper? To understand the specific reasons, let FrontStreet Coffee break it down for you.

The Purpose of Wetting Filter Paper:

1. Cleaning the Filter Paper and Removing Odors

Some might wonder 🤔️, aren't there already odorless filter papers bleached with bioactive enzymes? As long as you buy from reliable filter paper brands, this shouldn't be a concern, right?

However, everyone might be overlooking something: How do you store your filter paper? What's the storage environment like? FrontStreet Coffee once encountered a friend who left filter paper openly on a shelf, but he was a heavy smoker who often smoked at home alone. One can only imagine what the filter paper would become in that situation.

It can be said that "odorless filter paper can be both a blessing and a curse" – odorless filter paper actually absorbs odors more easily. Of course, if you store your filter paper sealed and separate, you don't need to consider this point.

2. Preheating the Filter Cup and Server

This point needs to be considered in relation to the material of your filter cup. If you have a resin filter cup, which doesn't absorb heat and has poor insulation properties, preheating doesn't significantly affect the brewing process. However, when using a ceramic filter cup, wetting the filter paper while preheating the filter cup becomes quite necessary. (For those interested in the insulation properties of different filter cup materials, click here)

Preheating the server ensures that when coffee extract comes out, its temperature won't drop too much, allowing for better appreciation of the coffee's flavors.

3. Better Fit with the Filter Cup

When you're not confident in your filter paper folding technique, you can press the filter paper with your hand while adding water to wet it. This can help the filter paper fit more snugly against the filter cup. Of course, if the technique is poor or the filter paper doesn't match the filter cup, wetting it still won't achieve a proper fit.

Considerations for Optimal Extraction

If you want your coffee extraction to be more uniform and reduce the influence of filter paper factors, the following three points about filter paper are worth careful consideration.

1. Bloom Degassing

After being wetted, filter paper softens and clings tightly to the filter cup. The grooves on the filter cup can't support the paper, which affects the effectiveness of bloom degassing.

2. Pre-extraction When Coffee Grounds Meet Wet Filter Paper

"Extraction" begins the moment coffee grounds come into contact with water. If you wet the filter paper and then pour dry coffee grounds into it, the coffee grounds near the filter paper will get moistened. Doesn't this cause some coffee grounds to be extracted in advance?

3. The Water Absorption Capacity of Filter Paper

A single sheet of filter paper absorbs about 8g of water. If completely wetted with water, the coffee extract won't seep upward. Therefore, after wetting the filter paper when brewing coffee, the filter paper remains nearly white. Without wetting the filter paper, the coffee extract will seep into the filter paper. This phenomenon is particularly noticeable when brewing dark-roasted beans – you can see the coffee-colored liquid gradually seeping upward.

Returning to our original customer's question, do you now understand why FrontStreet Coffee treats filter paper differently when brewing hot versus iced coffee?

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FrontStreet Coffee

No. 10 Bao'an Front Street, Yandun Road, Dongshankou, Yuexiu District, Guangzhou, Guangdong Province

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473