Technical guide
Portafilter filter baskets: single and double doses, blind baskets and diameters
A filter basket is chosen by its rim diameter, which has to fit the portafilter, by its dose and by its height. Single baskets take roughly 6–7 g and doubles 12–18 g or more; most groups use a 58 mm tamper and a 70 mm rim. A blind basket has no holes and is used for backflushing.
What is the difference between a single, a double and a blind basket?
A single basket holds one dose and usually narrows towards the bottom; a double holds two doses in an almost cylindrical body; a blind basket has no holes.
The La Marzocco Linea PB manual gives about 6–7 g for the small filter and 12–15 g for the large one. Deeper baskets exist for bigger doses: the same maker's range runs from 7 to 21 g. A blind basket never takes coffee: it closes the portafilter for backflushing the group. Bottomless portafilters use the same baskets. All of them are in Baskets & Shower Screens.
Which basket diameter does my portafilter take?
Most professional groups take baskets for a 58 mm tamper, but the rim diameter changes from brand to brand, and a few makers have smaller groups of 53 or 54 mm.
| Rim Ø | Tamper Ø | Typical groups |
|---|---|---|
| 70 mm | 58 mm | E61 and compatible, Faema, La Marzocco, Nuova Simonelli, Victoria Arduino, Rancilio, Wega |
| 68 mm | 58 mm | La Cimbali, Carimali, Gaggia |
| 66 mm | 54 mm | Dalla Corte, La San Marco |
| 65 mm | 53 mm | La Spaziale; some Wega and Astoria models |
The table follows a basket manufacturer's code guide; according to the same guide, 68 mm baskets have the body of the 70 mm ones with a rim 2 mm narrower. To confirm, measure the outer diameter of the rim, the inner diameter and the height with calipers.
How do basket height and dose relate?
The deeper the basket, the larger the dose it was designed for: at the same diameter, a few millimetres of height separate a 14 g basket from a 20 g one.
One manufacturer's figures for a 58 mm double series show it clearly: the 22.5 mm basket takes 13.5–15.5 g of dark-roast coffee; the 24.5 mm one, 16–18 g; the 26.5 mm one, 18–20 g; the 28.5 mm one, 20–22 g. With a light roast the same baskets take more: 20–22.5 g in the 24.5 mm basket. On the same maker's single baskets, a height of 18.5 mm corresponds to 6–10 g.
Work inside the basket's range: too much coffee touches the shower screen when the portafilter is locked in; too little leaves too much free space above the puck.
What do the retaining spring and the ridge on a basket do?
The basket retaining spring, housed in the portafilter, holds the basket in place; ridged baskets have a crease that the spring clicks into, while ridgeless ones are held only by the grip of the spring and come out more easily.
When the spring loses tension, the basket drops out as the puck is knocked out; the spring is replaced, not the portafilter. Springs differ in wire diameter (1.0 to 1.4 mm in the catalogue) and in shape, so pick the one for your portafilter. The springs are in Baskets & Shower Screens; spouts and portafilter bodies are in Group & Portafilter.
When should a filter basket be replaced?
When holes are blocked and will not clear, holes are enlarged, the bottom is deformed or cracked, or the rim is dented. The La Marzocco Linea PB maintenance plan has basket condition checked every three to four months and the baskets replaced every year.
- Cleaning: the La Marzocco and Nuova Simonelli manuals give about 30 minutes of soaking in hot espresso machine detergent solution, followed by a thorough rinse.
- Checking: hold the bottom up to the light; all the holes should show open and equal.
- Rim: a dented rim no longer seals against the group gasket and makes the portafilter leak.
FAQ
- Can I use a 58 mm basket from another brand in my portafilter?
- Only if the rim matches and the height fits the portafilter. Baskets for a 58 mm tamper come with 70 mm and 68 mm rims, and a deeper basket may not fit inside a spouted portafilter. Compare the rim diameter and the height with those of the basket you have.
- Which tamper should I use?
- The one that matches the inner diameter of the basket: 58 mm on most groups (some precision baskets accept 58.4 mm), 54 mm on Dalla Corte and La San Marco baskets and 53 mm on La Spaziale ones, according to a basket manufacturer's guide.
- Why does my basket hold more or fewer grams than stated?
- Because capacity depends on the coffee. The same basket takes more grams of a light roast than of a dark roast, and the grind matters too. Treat the stamped or advertised figure as a reference and adjust the dose within the basket's range.
- How do I read a code such as B70 2T H24.5 M on a basket?
- It is the coding used by one basket manufacturer, IMS: B70 is the rim diameter in millimetres, 2T means a two-cup basket (1T is a single), H24.5 is the height in millimetres and the final letter identifies the hole pattern. Other makers use their own codes, so always confirm the dimensions.
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