RADIAL UNIFORMITY OF
ESPRESSO EXTRACTIONS
STÉPHANE RIBES –MARCH 2020
RADIAL UNIFORMITY OF ESPRESSO EXTRACTIONS
TEST PROTOCOL
EY
espresso
EY puck
outside
EY puck
middle
EY puck
centre
Extraction Yield (EY) values
determined with TDS measurements
No paper filter V60 paper filter below the puck
Extraction yield radial distribution
•During a standard espresso
shot (no paper filter), the
extraction of the outer grinds
of the puck (1/4 of the total
dose weight) is only half the
extraction of the center
grinds
•With a paper filter below the
puck the extraction is much
more uniform
•This results in a considerably
increased average extraction
yield (21% →24%)
V60 PAPER FILTER BELOW THE ESPRESSO PUCK
Same grind setting for all shots (EK1.6)
12 grams dose in a 15g VST basket
The Force Tamper, Flat base, 58.5 mm
1:2.5 brew ratio
EY espresso
21%
25%
1%
18 29 mm25
Extraction yield radial distribution
EY espresso
24%
25%
1%
18 29 mm25
23% 24%
3% 2%
13% 22%
13%
4%
0-29 mm 0-29 mm
Convex tamper base (US curve)
Flat tamper base
•A convex tamper base
increases the flow in the
center of the puck
•The radial uniformity of the
espresso extraction is further
deteriorated and the average
extraction is lower
CONVEX TAMPER BASE
Same grind setting for all shots (EK1.6)
12 grams dose in a 15g VST basket
The Force Tamper, smooth bases, 58.5 mm
1:2.5 brew ratio
Extraction yield radial distribution
EY espresso
21%
25%
1%
18 29 mm25
Extraction yield radial distribution
EY espresso
20%
25%
1%
18 29 mm25
23% 22%
3% 4%
13%
7%
13%
19%
0-29 mm 0-29 mm
RADIAL UNIFORMITY OF ESPRESSO EXTRACTIONS
NEXT STEPS TO IMPROVE EXTRACTION UNIFORMITY
IMS
B702TFh22NT
49 mm
49 mm
40 mm
Reneka Micro-Sieve filter basket
VST 15g
precision basket
•With a diameter of 40 mm, the perforated surface area of the Reneka basket is
33% smaller than that of the Decent, VST or IMS baskets (49 mm diameter)
•Assuming that this could be the cause of the typical loss of Extraction Yield
of 3 points with this basket, it is reasonable to believe that an expansion of the
perforated area of precision baskets could improve the radial uniformity of
the extraction! (49 mm to 53 mm →+ 17% in the perforated surface area)
RADIAL UNIFORMITY OF ESPRESSO EXTRACTIONS
TEST PROTOCOL DETAILS
•Decent Espresso Machine DE1PRO v1.1 with a (red) Cafelat 8.0 mm silicone gasket
•IMS SI 200 IM screen (no spacer)
•Mahlkönig EK43 S grinder – SSP burrs “High Uniformity” with Silver Knight coating
•Montille water (Le Mont Dore, France) –adjusted to 50 ppm eq. CaCO3alkalinity and 125
ppm eq. CaCO3total hardness, with sodium carbonate and Epsom salts
•Complete drying of the basket and shower screen before each shot, with a clean tissue
•Single dosing of frozen beans ground in a double walled stainless steel cup
•12g of ground coffee in a VST 15g ridgeless filter basket
•WDT in the basket with a Londinium tool (and a Decent funnel) –no vertical tapping –gentle
raking of the coffee grounds with a hog tool, to obtain a uniform surface
•The Force Tamper with 58.5 mm smooth bases –flat base or US curved –used twice in a row
•TDS measurements: Atago PAL zeroed with adjusted Montille water –no filtering of the coffee
samples –all samples measured at room temperature after vigorous stirring
1 data point = average of 3 to 5 measurements of each coffee sample
HYBRID “LEVER-BLOOMING” PROFILE
2.5 ML/S EXTRACTION
•Combination of the Londinium and
blooming profiles
•The initial step “lock portafilter!”
is optional: it prevents exposure of
the coffee puck to the hot machine
environment during the final warm-
up of the brew water
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