Filter papers, cloth and metal

What a filter actually removes

Three things leave the brew bed: dissolved solids, which are the flavour; suspended fines, which are tiny particles of coffee; and lipids, the oils.

A filter cannot change the first. It decides how much of the other two reach the cup, and that decides the texture.

Paper

Paper holds back nearly all the oils and most of the fines. The result is the transparent cup that filter coffee is known for: acidity clearly separated, aromatics forward, very little weight on the tongue.

Bleached versus natural is not a filtering difference. Both are made to the same porosity. Natural paper is simply not bleached, so it carries more of its own papery flavour, which a rinse with hot water removes. Bleached paper today is oxygen-bleached, not chlorine-bleached, so the old objection no longer applies.

Thickness does matter. A Chemex paper is roughly three times heavier than a V60 paper, which is why a Chemex brew is slower, cleaner and thinner bodied even with the same grind and ratio.

Cloth

Cloth sits between paper and metal. It holds back the fines but lets a good part of the oils through, so a cloth-filtered cup has the clarity of paper with a rounder, softer mouthfeel. It is the traditional filter in much of Latin America and in the Japanese nel drip.

The price is maintenance. A cloth filter must be rinsed thoroughly, kept wet in the fridge or frozen between uses, and replaced when it starts to smell. A dry, neglected cloth turns rancid and every cup after that tastes of it.

Metal

A metal filter is a mesh with holes cut or etched into it. Holes are large enough that oils pass and so do many fines, so the cup arrives heavier, sweeter, slightly muddier, and it keeps developing as the fines carry on extracting in the carafe.

Use metal when you want that. Do not use it when you have bought a delicate washed Ethiopian lot and want to taste it clearly.

Choosing by what you want

You want	Use
Maximum clarity, bright acidity	Chemex paper
Balanced, everyday filter	V60 paper
Clarity with more body	Cloth
Heavy, textured, press-like	Metal

One more thing worth knowing: changing filter changes the flow rate, so it changes the grind you need. Swap the filter and re-dial, or you will blame the coffee for what the paper did.