On the table next to Golden, our coffee from Vietnam (100% robusta) sits beside Bon Café, our house blend (100% arabica). We sell them separately for a practical reason: robusta in a blend works best as a small share, and the right share depends on your cup. You can find it yourself with a scale and four espressos.
On 17 September we wrote about the difference between arabica and robusta in the cup: robusta has less sugar and almost twice the caffeine per gram. Today is about the question that comes next: how much robusta in a blend, and how you can tell you've added too much.
Why robusta in a blend works in small doses
Arabica brings the acidity and the aromas that change from one origin to another. Robusta brings body, a cocoa bitterness and some spice. The sheet for our Vietnam lot reads cocoa, sweet spices and roasted hazelnut. A little robusta fills the bottom of the flavour and lets the arabica speak on top. Too much covers everything in bitterness, and a weak robusta adds a taste of rubber or burnt wood.
Complete Home Barista, an espresso guide for home brewers, puts the marker at 10-20% robusta for black espresso and above 30% for milk drinks, where arabica's finer aromas get lost anyway. The crema gets thicker, but yesterday we showed that crema thickness says little about taste. The sip decides.
The home test: robusta in a blend at 0, 10, 20 and 30%
You need the arabica you usually drink, a bag of robusta and a scale that reads to 0.1 g. Weigh the whole beans, mix them and grind them together at your usual espresso setting. That's the easy way to make an arabica robusta blend at home without dosing by eye.
For an 18 g basket:
- 0%: 18 g arabica, the reference cup
- 10%: 16.2 g arabica and 1.8 g robusta
- 20%: 14.4 g arabica and 3.6 g robusta
- 30%: 12.6 g arabica and 5.4 g robusta
Pull 36 g into the cup each time and keep the same grind. Drink them black, in this order, with a sip of water in between. If you drink cappuccino or flat white, make the 20% and the 30% again with your usual milk: robusta in a cappuccino shows its purpose fastest.
Using a moka pot? If your funnel takes 15 g, the ladder becomes 13.5 g and 1.5 g, then 12 g and 3 g, then 10.5 g and 4.5 g. Write down what you taste in each cup. A robusta espresso test at home takes one morning and tells you more than any bag labelled "intense".
Reading robusta in a blend: if you taste X, do Y
- At 10%, the black espresso is rounder and the arabica's acidity feels softer: that's your robusta percentage for espresso.
- In the cappuccino, the coffee disappears under the milk at 10% and 20%: go up to 30% for milk drinks and stay at 10% for black ones.
- At 20%, a rubbery or burnt-wood finish shows up: go back to 10%. If the bitterness stays, check your grind with the too-fine grind test.
- Your pure arabica espresso comes out sour and runs fast: the problem is extraction. Check first with the two-cup test, because robusta would only mask the fault.
- You drink coffee in the afternoon: at 20-30% robusta, the cup holds noticeably more caffeine than pure arabica. Keep that in mind for the 4 pm coffee.
Robusta in a blend, roasted the same day on Golden
On the product pages, the coffee from Vietnam and Bon Café share the same roast date: Saturday 10 October 2026, sunny, 12°C, 85% humidity, wind at 6 km/h. Laurent roasted them separately. Our Vietnam robusta roasted outdoors went to medium-dark, while the arabica blend stopped at medium. The robusta bean holds less sugar and colours more slowly, so Laurent gave it a different path through the fire on Golden.
For your test, this is what counts: two bags from the same weekend got the same air, the same hands at the fire and the same days of rest. At home, you change only the percentage. Next weekend the air will be different, Laurent will adjust the fire to it, and the flavour target stays the same.
A good robusta states its origin and roast date. The trade takes it more seriously every year: on the cupping scale, a robusta scoring 80 points or more is called "fine robusta", and in May 2025 Brazilian researchers led by Fabiana Carvalho published a flavour wheel built specifically for robusta in Scientific Reports. If you're looking for robusta coffee in Anderlecht, the Vietnam product page shows both details.
The bags from 10 October have sold out, and the product pages let you reserve for the weekend. Or come straight to the Marché de l'Abattoir on Saturday and Sunday, exit of the Manufakture car park, Anderlecht. Run the four-cup ladder and tell us where you stopped.
Brut. Sauvage. Imprévisible.
