What are Chemex Bonded Filters?
The thickest mainstream coffee paper, and the reason a Chemex tastes the way it does.
Chemex publishes specialty fibre paper 20 to 30 percent thicker than other filters, natural unbleached square sheets, manufacture in the USA from North American materials, compostability, and 200 sheets across two boxes. The maker attributes the removal of bitterness, acidity and sediment to the thickness.
Why thickness changes the cup more than the brewer does
A Chemex is a glass funnel. The filter is the technology.
Thicker paper does two things at once. It filters more finely, so more of the oils and the very fine particles are held back, which is what produces the exceptionally clean, tea-like cup a Chemex is known for. And it slows the flow considerably, which extends contact time and changes extraction.
That is why a Chemex brewed with a thin generic filter does not taste like a Chemex. The vessel is doing very little; almost all of the character comes from the paper. It is the same relationship the V60 has with its own filters, only more pronounced.
It is also why Chemex recipes call for a coarser grind than a V60 at the same dose. The paper is already slowing things down, so the bed does not need to.
The fold, and the thick side
The one piece of technique this product needs, and it is not obvious.
Chemex filters fold into a cone with three layers on one side and one on the other. That thick side goes against the pouring spout of the Chemex, not away from it.
The reason is airflow. The channel in the Chemex neck needs to let displaced air out as water goes in, and the three-layer side holds the paper off the glass enough to keep that channel open. Fold it the other way and the brew stalls, which is the most common complaint from new Chemex owners and is not the filter's fault.
Chemex filters vs a reusable metal filter
Opposite ends of the same axis, and a metal filter defeats the point of a Chemex.
A reusable metal filter costs nothing to run and passes oils and fines, producing a heavy, textured cup.
That is the exact opposite of what a Chemex is for. If you like the clean, bright, sediment-free cup, the paper is the product and the glass is the holder. Buying a Chemex and fitting a metal filter to save money gets you a worse French press.
Are they worth it?
Yes, and there is no real alternative if you own the brewer.
200 sheets at a few pence each is cheap against the coffee going through them, and third-party Chemex-shaped filters are almost always thinner, which changes the brew.
Chemex publishes no thickness figure in microns, only the relative claim, so the 20 to 30 percent is a comparison rather than a measurement you can check. Made in the USA, compostable and the fibre type are all published.
Who should buy them (and who should not)
Buy them if you own a Chemex, and buy the right shape.
These are the natural square sheets. Chemex also sells circular pre-folded and half-moon versions, and the square is the classic. 200 is a sensible pack for daily brewing.
They are not a general-purpose cone filter, so do not buy them for a V60. And if you like body and oils in your cup, this is the wrong brewer and the wrong filter; a French press is the honest answer.
Frequently Asked Questions
Why are Chemex filters so thick?
Chemex publishes them as 20 to 30 percent thicker than other filters. The thickness is what removes oils, fines and sediment, and it is what gives a Chemex its clean cup.
Which way do you fold a Chemex filter?
Into a cone with three layers on one side, and that thick side goes against the pouring spout. Folded the other way, the air channel closes and the brew stalls.
Can I use a normal cone filter in a Chemex?
It will fit, but it is thinner, so the brew runs faster and tastes different. The paper is most of what a Chemex does.
Are they compostable?
Yes, and Chemex publishes them as made in the USA from North American materials.
