Filter Coffee: Numbers, Myths, and the Paper Filter Effect

Filter coffee is the most consumed and worst-documented brewing method there is. Almost every number that circulates about it – 4 to 8 minutes, 1.15 to 1.35 percent, the Golden Cup Standard – is either no longer accurate, or was never quite as accurate as it's been passed down. Here they are, with dates and sources.

Up front: none of this tells you how your coffee should taste. Numbers make a result repeatable, not right. If a coffee outside every target range tastes better to you, that's not a mistake – you've just found your range.

What Is Filter Coffee, Exactly?

Filter coffee means water runs through a bed of ground coffee, and the finished coffee is separated from the grounds in the process. Technically, that's percolation – the water moves through the coffee bed and constantly meets fresh material as it goes. The counterpart is immersion: with a French press, or during Specialty Coffee cupping, the coffee sits in the water and is only roughly separated at the end.

This difference isn't just academic. It determines how many fine particles and how much oil end up in the cup – and with that, the body, the clarity, and, as you'll see further down, your blood lipids.

Who Invented the Coffee Filter?

Melitta Bentz, 1908, in Dresden. That's well documented, but it's told wrong almost everywhere.

On June 20, 1908, she filed a utility model, described as "a coffee filter with a base that is curved and recessed on the underside, with obliquely angled flow holes." It was registered on July 8, 1908, on page 1145 of the Imperial Patent Office's Patentblatt in Berlin. On December 15, 1908, the commercial register entry for the firm "M. Bentz" followed, at Marschallstrasse 31 – starting capital, 72 Reichspfennig.

Two details regularly get twisted here: it was not a patent, but a utility model. And it was not the 19th century, but 1908. The dates come from the German Patent and Trademark Office (DPMA).

Where Do the Numbers on Filter Coffee Come From?

From the 1950s, and from a single research program, to be precise. Around 1952, the US National Coffee Association founded the Coffee Brewing Institute. Its first director was Ernest E. Lockhart, a food scientist who had earned his doctorate at MIT in 1939. In 1957, he published The Soluble Solids in Beverage Coffee as an Index to Cup Quality – which gave rise to the Brewing Control Chart that still hangs on the wall of every café today.

You'll often read that the chart was "developed at MIT." The sources don't support that: MIT is where Lockhart earned his doctorate; the coffee research itself was carried out at the Coffee Brewing Institute. We found no source confirming where the research took place.

What's striking is how thin the underlying evidence is. A research group at the University of California, Davis re-examined the chart in 2023 and writes that neither the chart itself nor the source material makes clear which people actually found the coffee at the center of the chart ideal. Their verdict on the "ideal" coffee marked there: misleading, and possibly simply inaccurate.

Is the Golden Cup Standard Still in Effect?

Not as a numbered standard. And that's more than splitting hairs.

Golden Cup and what applies today

Schematic. The diagonals of the original chart (brew ratio) have been omitted here.

The familiar figures – 18 to 22 percent extraction yield, 1.15 to 1.35 percent dissolved solids – appear in the SCA document Coffee Standards, Revised 2018, section 5.1. That document is still on the SCA website, but it no longer appears in the current standards catalog and carries no SCA number.

Today's catalog has no standard for brewing parameters. Published standards cover cupping (SCA-102 through SCA-105), equipment (SCA-310 for home brewers, SCA-320 for grinders, SCA-350 for espresso machines), training rooms, and the qualification of judges. A brewing-parameter standard isn't among them – nor is one in development.

To be upfront about it: we found no explicit statement from the SCA that the Golden Cup Standard has been withdrawn. All that's documented is that it's missing from the current catalog. That conclusion is drawn by this article, not by the SCA.

It gets curious when you compare the numbers: the range the SCA certifies home brewers against today is 1.15 to 1.55 percent – considerably wider at the top than the classic 1.35. So if someone cites "the SCA figure," they need to say which one they mean.

What Brew Temperature and What Ratio?

The three numbers that matter

The current equipment standard, SCA-310-2021, is specific here. A certified machine must be between 90 and 96 degrees at the latest by the time a third of the water has been sprayed on – measured in the coffee bed itself, with three floating probes, not in the tank. As a standard ratio, the standard works with 55 grams of coffee per kilogram of water, or roughly 17 grams per 300 milliliters.

For the carafe afterward: 80 to 85 degrees over the first 30 minutes, never above that. If you've ever left coffee sitting on a hot plate, you know the rest.

How Long Should Filter Coffee Brew?

As long as it needs to. There's no valid requirement for this – and that surprises most people.

The famous four to eight minutes comes from the requirements of the SCA's home brewer certification program from 2017. It stated, literally, that contact time had to be "more than 4 minutes, but less than 8 minutes." The successor standard, SCA-310-2021, no longer includes any brew-time requirement. Run time is still measured, but only to determine the point at which temperature is measured.

That makes sense, too: in a percolation brew, brew time is a result of grind size, filter, and pouring technique – not a dial you can turn directly. For how to put that to use in practice, see our V60 guide.

Is Filter Coffee Healthier Than Unfiltered Coffee?

On one point, there really is a documented difference, and it has to do with the paper.

Coffee contains two diterpenes, cafestol and kahweol. Hot water dissolves them, but most stay trapped in a paper filter. In controlled studies, cafestol measurably raised cholesterol levels: in a randomized trial from 1997, total cholesterol rose by around 31 milligrams per deciliter over four weeks at a dose of 61 to 64 milligrams of cafestol daily. A 2012 meta-analysis of twelve controlled studies with just over 1,000 participants found, on average, just over 8 milligrams per deciliter more total cholesterol – with the larger increase in unfiltered coffee.

What the paper filter holds back

Very small sample sizes per category (three to eleven samples). Paper-filter coffee contains little cafestol, not none.

Just how large the difference between brewing methods is shows up especially clearly in a Swedish 2025 measurement series. Scandinavian boiled coffee had a median of 939 milligrams of cafestol per liter, homemade paper-filter coffee just 12. The same boiled coffee poured through a cloth filter dropped to 28.

At the level of entire lifespans, a Norwegian cohort study looked into it in 2020: 508,747 people, followed for an average of 20 years. Filter coffee was associated with lower all-cause mortality than no coffee at all; unfiltered coffee performed worse than filter coffee.

How do official bodies classify this? Norway is the only country where we found an explicit recommendation: the Norwegian Directorate of Health states that one to four cups of filtered coffee a day can be part of a healthy adult diet, and in the same breath defines boiled coffee and plunger (press-pot) coffee as unfiltered. The Nordic Nutrition Recommendations 2023 advise against high consumption of boiled coffee.

For the European Food Safety Authority, Germany's Federal Institute for Risk Assessment (BfR), and the relevant Swiss authorities, we found no statement on coffee diterpenes – there, the focus is exclusively on caffeine. That doesn't mean none exists; we simply didn't find one. And needless to say, this section doesn't replace a conversation with your doctor.

What Grind Size and What Bean?

For grind size, direction matters more than the number. The SCA equipment standard gives a target range of 425 to 850 microns for conical filters and 589 to 1,198 microns for flat-bottom filters – roughly speaking: about like coarse sea salt, noticeably coarser than for espresso.

In practice, you don't need a sieve analysis for this, just two observations: if the coffee runs through very fast and tastes thin and sour, grind finer. If the water sits for a long time and the coffee turns scratchy and dry, grind coarser. What you need for that is a grinder with reproducible settings – you'll find a selection among our coffee grinders.

When it comes to the bean, there's no right answer. Lighter roasts show more fruit and acidity in the filter, darker roasts more chocolate and body. How any given arabica variety tastes also depends on origin and processing – and ultimately on you. If you want to know what that score on the bag actually means: Specialty Coffee.

What Water?

Here, the evidence gets messy, and we'd rather say so than hand you a single number.

The 2018 SCA document lists target values of 150 milligrams of dissolved solids per liter, calcium hardness around 68 milligrams per liter, alkalinity near 40 milligrams per liter, and a pH around 7.0. The SCA-310 equipment standard from 2021 refers to "the current SCA water standard" and cites different figures: 50 to 175 ppm calcium hardness and pH 6 to 8.

There is currently no water standard at all in the numbered SCA catalog, and two SCA documents cite different figures. Which ones apply today can't be answered definitively from public SCA sources. What holds up in practice: no chlorine, not rock-hard, not distilled.

Frequently Asked Questions About Filter Coffee

What is filter coffee?

Filter coffee is coffee where hot water runs through a bed of ground coffee, and a filter separates the finished coffee from the grounds. That's what distinguishes it from full-immersion methods like the French press, where the coffee sits in the water and is only roughly strained at the end.

What brew temperature is right for filter coffee?

The current SCA equipment standard, SCA-310 from 2021, requires 90 to 96 degrees, measured in the coffee bed itself. In practice, that means: boil your water and let it sit for about a minute, and you'll be in that range.

How long should filter coffee brew?

There's no binding requirement. The often-cited four to eight minutes come from the SCA certification program of 2017; the current standard, SCA-310-2021, no longer specifies a brew time. Brew time is a result of grind size and filter, not a target in itself.

What coffee-to-water ratio is right?

55 grams of coffee per liter of water has become the standard starting point – that's roughly 17 grams per 300 milliliters. This figure also appears in the current SCA equipment standard. Whether stronger or milder tastes better to you is a separate question.

Is the Golden Cup Standard still in effect?

The figures 18 to 22 percent extraction and 1.15 to 1.35 percent dissolved solids come from the SCA document "Coffee Standards, Revised 2018." Neither a Golden Cup Standard nor a standard for brewing parameters appears in the SCA's current, numbered standards catalog. However, the SCA has not published a formal withdrawal.

Who invented the coffee filter?

Melitta Bentz, of Dresden. On June 20, 1908, she filed a utility model, which was registered on July 8, 1908, in the Patentblatt of the Imperial Patent Office. It was explicitly a utility model, not a patent – and it was 1908, not the 19th century.

Is filter coffee healthier than unfiltered coffee?

There's a documented difference in cholesterol levels: a paper filter largely retains the diterpenes cafestol and kahweol, which raised LDL levels in controlled studies. A Norwegian cohort study of just over 500,000 people found lower mortality with filter coffee than with unfiltered coffee over twenty years. That's observational data, not proof of causation – and unfiltered coffee did not perform worse than no coffee at all in most groups.

What grind size does filter coffee need?

Noticeably coarser than espresso, about like coarse sea salt. The SCA equipment standard gives a target range of 425 to 850 microns for conical filters. Direction matters more than the number: if the coffee runs through too fast and tastes thin, grind finer. If the water sits and the coffee turns scratchy, grind coarser.

Now What?

The most useful first step isn't buying a refractometer, but brewing two carafes side by side: one at 55 grams per liter, one at 65. The difference is big enough that you'll notice it immediately – and afterward, you'll know where your range lies, instead of where 1957's did.

Step by step, that's covered in our V60 guide. If you want to do the same thing with espresso: Espresso Dial-In. And if you'd rather go through it once with guidance, join a workshop in Bern or Zurich. We're United by Coffee – whatever your brewing method.

Sources and Context

• Invention of the coffee filter: German Patent and Trademark Office (DPMA), entry on Melitta Bentz (filed June 20, 1908; registered July 8, 1908, page 1145 of the Patentblatt; commercial register entry December 15, 1908).
• Golden Cup Standard: Specialty Coffee Association, Coffee Standards, Revised 2018, section 5.1. That no brewing-parameter standard and no Golden Cup Standard is listed in the current standards catalog is a negative finding based on the SCA's official standards list.
• Brew temperature, ratio, grind size, holding temperature, absence of a brew-time requirement: SCA Standard 310-2021, Home Coffee Brewers: Specifications and Test Methods.
• Contact time "more than 4, less than 8 minutes": SCA, Minimum Certification Requirements for Coffee Brewers, Certified Home Brewer Program, 2017 – a superseded program version.
• Coffee Brewing Institute, Lockhart, and the 1957 publication: Emma Sage, The Coffee Brewing Institute, SCA News 2013; Frost, Batali, Guinard, Ristenpart, Towards a New Brewing Chart, 25 Magazine No. 13.
• Critique of the classic chart: Guinard et al., A new Coffee Brewing Control Chart relating sensory properties and consumer liking to brew strength, extraction yield, and brew ratio, Journal of Food Science 88(5), 2023.
• Diterpenes and cholesterol: Urgert & Katan, Annual Review of Nutrition 17, 1997; Urgert et al., American Journal of Clinical Nutrition 65, 1997; Cai et al., European Journal of Clinical Nutrition 66, 2012.
• Cafestol content by brew method: Orrje et al., Nutrition, Metabolism and Cardiovascular Diseases 35, 2025.
• Cohort study: Tverdal et al., Coffee consumption and mortality from cardiovascular diseases and total mortality, European Journal of Preventive Cardiology 27(18), 2020.
• Official guidance: Helsedirektoratet (Norway), Kostrådene, as of August 15, 2024; Nordic Nutrition Recommendations 2023, Beverages chapter.
• We have no statement from EFSA, BfR, or Swiss authorities regarding coffee diterpenes; this is noted as such in the text.