The kettle clicks, the water is still rolling and you pour it straight onto the coffee. Some people will tell you that's how it's done. Others will say you just burned it. Both camps are half right. You can use boiling water for coffee without worry, on one condition: you need to know how far the beans in your bag were roasted.
We covered the ratio a week ago in the piece on the coffee to water ratio. Today the ratio stays fixed and only the water moves.
Where the fear of boiling water for coffee comes from
The idea that boiling water burns coffee comes from the kitchen, where 100°C is a lot. For a coffee bean, 100°C is very little. At Golden, the beans tumble in the hot drum and come out at the end above 200°C. Whatever could burn in the bean already did, at twice the temperature of your kettle.
So what does hot water actually do? It dissolves faster. Acids and sugars come out first, bitter compounds later. With boiling water, that whole sequence speeds up. Add a fine grind and a long contact time, and you reach bitterness sooner. That bitter, dry taste on the tongue is what people call "burnt".
Plenty of us use the same kettle for tea and coffee, with the same habit: click, pour. The habit works fine, as long as you know your bag.
Boiling water for coffee or 87-93°C: what UC Davis tested
What water temperature for coffee? In 2020, three UC Davis researchers (Batali, Ristenpart and Guinard) published a filter coffee test in Scientific Reports. They brewed at 87, 90 and 93°C and adjusted grind and time so every cup had the same strength and the same extraction yield. Tasters found no meaningful difference between the cups.
The study stops at 93°C, so for boiling water we draw the conclusion indirectly. What it shows clearly is the rule underneath: taste depends on how much dissolved and how strong the cup is. Water temperature for pour over is a speed dial. Change it, and you make up the difference with grind or time.
One more kitchen detail. Water loses heat on the way: through the air, into a cold dripper, into the cup. What reaches the coffee bed is cooler than what sat in the kettle, even when you pour right off the boil.
Boiling water for coffee roasted light, a minute's pause for dark
This is where the bag comes in. A light roasted bean is denser and dissolves more slowly, so boiling water helps. A bean taken further is more porous and gives up its solubles quickly. Water temperature for dark roast coffee can come down: leave the kettle a minute with the lid open, or grind one step coarser.
How far each batch goes is Laurent's call at Golden. In the morning Laurent reads the weather and adjusts the flame and the time to hit the same target, in cold or in wind. That target stays the same from one weekend to the next. For you, it means the water temperature you find for one coffee still works for the next bag of the same origin. The batches meant for filter are described in our piece on coffee roasted for filter. They usually want water as close to boiling as you can get.
Tomorrow's test: boiling water for coffee or a minute's pause
You need two cups and your usual recipe. We work with 15 g of coffee to 250 g of water.
- Grind 30 g at your usual setting and split it into two equal doses.
- Cup A: pour right after the kettle clicks.
- Cup B: leave the kettle a minute with the lid open, then pour. How long to wait after the kettle boils? One minute is enough to lose a few degrees. Exactly how many depends on your kettle and how much water is in it, so if you own a kitchen thermometer, measure your own kettle once and remember the number.
- Let both cups cool for 5 minutes, then taste one after the other.
How to read the result:
- If B comes out thinner and sour, your bag wants boiling water. To tell sourness from acidity, see our two cup test.
- If A comes out bitter and dry on the tongue, keep the minute's pause or grind one step coarser.
- If you taste no difference, you just repeated the UC Davis result in your own kitchen. Pick whichever is easier.
One step matters more now in October: preheat the dripper. After today's warm day, the Open-Meteo forecast for Brussels shows lows around 9°C towards the weekend, and the kitchen cools down with them. A cold ceramic dripper pulls heat from the first pours. Rinse the dripper and the cup with hot water, tip the water out, then add the coffee.
This weekend you'll find coffee roasted outdoors in Anderlecht, at the Marché de l'Abattoir (exit of the Manufakture car park), on Saturday and Sunday. Tell us at the stand how your test went, and we'll tell you how far Laurent took the batch in your bag. If you'd rather choose ahead, the coffee catalogue is online.
Brut. Sauvage. Imprévisible.
