Paper filters have a reputation for giving your cup of coffee a cleaner and more vibrant flavour when compared to filters made from other materials, such as cloth and metal.

But with a range of paper filters on the market, all varying in size, shape, and thickness, it can be difficult to choose the best one for your brewer.

To learn more, I spoke with two Brewers Cup Champions: the 2018 Indonesian Champion, Hiro Lesmana, and the two-time Romanian champion, Gabriel Carol. Read on to find out what they said.

You may also like our article on how filter basket shape affects the flavour of your coffee.

What should you look for in your paper filter?

According to Hiro and Gabriel, people often don’t think enough about which paper filter to use when brewing pour over coffee. Understanding how they are made, which materials used in their manufacture, and how their composition affects extraction can all inform the brewing process.

But first, let’s take a step back and look at exactly what we want from our coffee filters.

A filter’s basic function is simple: it must separate the grounds from the brewing water during extraction to produce a clean-tasting filter coffee, with minimal or no sediment.

However, beyond this, the actual quality of paper filters can also vary significantly. Differing levels of thickness and porosity change how efficiently your paper will extract the aromatics and oils from ground coffee, ultimately altering the mouthfeel and flavours you experience in the cup.

Consider what your filter paper is made of, for starters. A range of raw materials are used to manufacture filter papers, from mineral fibre pulps and fibre crops to softwoods and hardwoods. 

Fibre length typically determines the porosity of the filter paper, which subsequently has an effect on the compounds and oils that are extracted into the final cup.

Bamboo and abaca (also known as Manila hemp) have the longest fibres of all of the common raw materials used to manufacture filter paper, and are consequently more porous (meaning more oils make their way into your cup). In contrast, eucalyptus pulp has the shortest fibres, and is the least porous of all the pulps used to manufacture filter paper.

Finally, you’ll need to think about the size and shape of the filter paper. Capacity and compatibility with your brewer are arguably the two most important factors here. Each filter will hold a varying amount of water and ground coffee, and each will be suited to a specific shape (such as a flat bottom or conical dripper, for example)

Flat bottom or conical?

Making sure your filters fit your brewing device should be a priority when making your choice. There are two main styles of pour over brewers – conical and flat bottom – and each have their own unique characteristics that affect extraction.

The Hario V60 and the Chemex are two of the most popular conical brewers available today, while the Kalita Wave and the Fellow Stagg X are common flat bottom brewers. Each uses their own corresponding shape of filter paper.

Cone-shaped brewers tend to extract more quickly, which Gabriel says brings out more vibrant aromas and “juicier” acidities. Conversely, he argues that flat bottom brewers tend to extract more slowly, bringing out more of a coffee’s body.

According to research from the SCA and UC Davis, there are substantial differences in the cup profile delivered by both flat bottom and conical brewers, in terms of the flavours and aromas extracted. 

The SCA and UC Davis study explains that the differences in shape between the two brewers influences the flow of water throughout extraction. As flow rate changes, it alters what scientists refer to as “mass transfer” – the speed at which water moves through the ground coffee.

The study found that for lighter roasts, flat bottom brewers yielded more sweet and floral notes, while conical brewers brought out slightly heavier and berry-like flavours.

For darker roasts, the flat bottom drippers brought out more chocolate, woody, and nutty notes in the cup. In contrast, cone-shaped brewers enhanced the bitterness.

How are paper filters made?

Filter papers can be fully plant-based or made using a mixture of source materials – which can be a combination of natural, synthetic, and even glass fibres.

“[Once you have the fibres], the papers are then press-heated together on the sides to make a conical shape, or whatever shape it needs to be,” Hiro says.

Once the fibres have been press-heated into a filter, the manufacturer will then decide whether or not to bleach them.

It’s easy enough to tell if your filters have been bleached during manufacturing; if they’re brown or have a distinct “natural” colour to them, then they’re unbleached. If they’re a uniform white, this indicates that either chlorine or oxygen have been used to bleach the fibres. 

While there is no research to suggest there is a difference in flavour between oxygen and chlorine-bleached filters, studies do indicate notable differences between unbleached papers and those bleached with oxygen. Most importantly, unbleached filters tend to give the final cup a “papery” flavour and aroma.

This is one of the reasons that both baristas and home coffee consumers “pre-wet” their filter papers before brewing. By wetting the paper with warm water, you rinse away any papery flavours; it also helps the filter fit into the brewer by eliminating any air pockets, and preheats the dripper and your vessel.

Today, most filter paper manufacturers lean towards oxygen bleaching. Oxygen-bleached paper biodegrades more quickly, as chlorine bleaching produces dioxins and other toxic pollutants which bond to carbon-based compounds – such as lignins – and remain intact for longer.

Adjusting your pour

Gabriel says that he thinks the majority of “experienced baristas” prefer unbleached paper filters, which have more tightly-knitted fibres. 

Hiro explains that the more tightly-knit the fibres are, the higher the paper’s density capacity will be. Denser papers provide more clarity in the cup, but are harder to use, according to Hiro.

He says this is because the drawdown during extraction takes longer than it does with less dense paper filters. “This means it would be easier for your brew to go wrong, causing overextraction or bitterness,” says Hiro. 

In contrast, loose-knit paper filters are easier to use because the drawdown is faster, but the end result means less clarity and vibrancy in the cup.

Both Hiro and Gabriel prefer abaca-based papers. According to Gabriel, these are designed to solve two problems brewers commonly encounter with their filters: the papery flavour in the cup, and the lack of resistance during extraction.

However, Gabriel also notes that extracting papery flavours into the cup is often a consequence of poor pouring control. He explains that it is normal for inexperienced brewers to have less control over their flow rate during the pour.

As such, Gabriel recommends using filters that are at least 0.15mm thick, because the higher density slows down the flow of water – resulting in less body but more pleasant acidity.

Thinner papers also should be used with coarser coffees and lighter roasts, but brew time should be extended. Hiro explains: “[It’s] harder [for coarser grinds and lighter roasts] to [dissolve], so they usually have a longer brew [time]”. 

In contrast, thicker paper filters are ideal for darker roasts and finely ground coffees, which are both easier to extract – meaning the total brew time is faster. Thicker paper filters will help to offset this.

For beginners, Hiro says it can be worth using steep-release immersion hybrid brewers, like the Clever Dripper or Hario Switch, with light and medium roasts.

“There’s no perfect recipe for succeeding at your coffee game,” he concludes. “The best will be the one that gives you the best result.”

Tips from champion brewers

Both Hiro and Gabriel say that experimentation is key when fine-tuning your extraction and brewing coffee to best suit your tastes. In line with this, they recommend trying different paper filters to see what works best for you.

“I use thick filter papers (0.28mm) [for dark roasts], thinner [filters] (0.15mm) [for medium roasts], and abaca filters for medium to light roasts,” Gabriel says. He recommends a brew time of 2:10 to 2:20 minutes, which he believes is the “sweet spot” for his brews. 

Gabriel suggests using 12g for medium or light roasts and 13g for dark roasts, at a medium grind. He says the water temperature for lighter roasts should be around 92ºC, and around 87ºC for dark roasts.

“Start pouring 30g of water and let it bloom for 30 seconds. Then pour into the centre of the dripper with a thin stream until it reaches 100g,” he says.

“Repeat that process, stop, and then keep pouring while maintaining the same speed. The last 90g of water should be divided into 2 pours (45g/45g).”

Hiro uses a different recipe: he says to start with 16g to 19g of medium-coarse coffee, and to aim for a total brew weight of 250ml to 300ml. The water temperature should be between 93ºC to 95ºC. For those who don’t own a temperature-controlled kettle, Hiro suggests leaving the kettle at room temperature for 5 minutes after boiling.

When pre-wetting his filter, Hiro uses a spoon to press the paper down into the dripper – this, he says, helps it to fit snugly into the brewing chamber.

To begin, he says to bloom with two to three times the weight of the ground coffee (for example, 15g would equate to 30ml to 45ml for the first pour). Your first pour should take no more than 10 seconds, and you should then gently swirl the brewer to saturate all the grounds evenly. 

After leaving the slurry to bloom for 30 to 50 seconds, Hiro then recommends pouring the rest of the water more vigorously, aiming for a final brew time of between two and a half to three minutes.

While there’s already no shortage of things to consider when calibrating your brew recipe – including grind size, dose, and brew time – thinking about your filter papers can help you fine-tune the resulting cup profile.

Next time you’re shopping for filters, maybe think about trying something new: maybe a different material or a slightly thicker paper? Record the differences somewhere and reflect on how it changes the flavours and aromas in your cup. You never know – the results might surprise you.

Enjoyed this? Then read our article four ways to make “paperless” coffee at home

Photo credits: Gabriel Carol, Hiro Lesmana, Taste Coffee Shop

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