There are a number of different ways to filter coffee. Some of the more common types of filters are paper, metal, cloth, plastic and glass. Some filters are very porous while others – even of the same material – are very fine.
Whatever type of filter you use, you should match your bean grind to that filter, Failure to use the right size grind can result in a clogged filter or a lot of sludge in your coffee cup. Matching the grind to the filter you are using will improve the taste of your coffee.
Coffee grinders often have labels on them relating to the brew method. But it isn’t the brew method that dictates the size of the grounds – it is the filter. An automatic drip coffee maker with a paper filter uses a medium grind but an automatic drip brewer with a gold metal filter requires a coarser grind. If you make a manual pour over coffee with a paper filter the grind can vary from coarse to extra fine depending on the type of filter paper.
If the grind is too fine for the filter, the extraction time will be extended and the coffee will be acidic and bitter. In extreme cases, the filter will clog and the only coffee will be on the floor. If the grind is too coarse for the filter, the extraction time will be too short and the coffee will be weak and sour.
The size of the holes in the filter determines what type of grind to use. Filters with larger holes such as plastic and metal filters allow solids to pass through into the brew – they need coarse grinds to limit the solids. Filters with medium holes hold back the solids – they need medium grinds. Filters with small holes take fine grinds. However, if the holes are too small the fine grinds will clog the filter (e.g Chemex) and you have to use a medium grind.
Here is a chart to help you decide which grind setting to use:
|Glass (Cona brewer)||Medium Fine|
|Metal (e.g French Press)||Coarse|
|Moka Pot metal||Fine|
|Gold metal||Medium Coarse|
|Paper cone (Melita)||Medium Fine|
|Paper flat bottom (Bunn)||Medium|
|Keurig K Cup||Medium Fine|
|Hario paper||Medium Fine|
|Aeropress metal||Varies from Fine to Medium|