How to Brew Light Roast Coffee: Water Temperature, Bloom and Grind Size

Light roast tastes thin if you brew it like a dark roast

Have you ever brewed a light roast at home and found it weaker than the same coffee in a cafe, or sour without any sweetness? The reason is not your technique. A light roast and a dark roast are physically different beans.

A lightly roasted bean still has much of its cell structure intact. It is hard, and its compounds dissolve into water reluctantly. A darker bean becomes brittle as roasting continues, so it gives up its compounds with far less effort. Brew them the same way and only the light roast comes out under-extracted.

The good news is that there are not many things to change. Below is the approach we actually use at HITACHINO COFFEE, in order.

1. Do not lower the water temperature

Temperature matters most. We brew light roasts at 92-96C. For the very lightest roasts, 97-100C is sometimes recommended.

You may have heard that hot water brings out harshness, or that cooler water makes coffee sweeter. That holds for dark roasts, but it works the other way around with light roasts. For a light roast, heat is not a way to make the cup stronger. It is the means of dissolving compounds that would otherwise stay locked in the bean. Brew too cool and what comes forward is not sweetness but green, underdeveloped flavour.

Water poured from a kettle into a serving pot will have dropped to around 95C by the time you start pouring. Without a thermometer, boiling and then waiting about a minute is a reasonable guide.

There is no need to drop the temperature late in the brew

Some methods switch to cooler water for the final pours. With light roasts this works against you. Pour at the same temperature throughout.

2. A short bloom is enough

The bloom, where you wet the grounds and wait about thirty seconds, exists to release carbon dioxide left in the bean after roasting. Light roasts hold less of that gas to begin with. The further a roast goes, the more gas it retains, so blooming does more for a dark roast and less for a light one.

If the bed does not dome, nothing has gone wrong. Move on to the next pour after 20-30 seconds. Holding the temperature matters more than extending this step.

3. Use 14-15g per cup

We use 14-15g per cup as our guide, which makes about seven cups from 100g and twenty from 300g. Start with 220-240ml of water. If the cup is too strong, add water; if it is too weak, add coffee. Adjusting in that order keeps things simple.

Cutting the dose and adding water gives you a cup that is not only weak but astringent. Adding coffee is the safer correction.

4. Start at a medium-fine grind, and ignore the fines

Begin at medium-fine, somewhere between granulated sugar and coarse sugar. If the brew finishes too quickly, grind finer; if the water stalls in the bed, grind coarser.

Sifting out the finest particles with a sieve is a known technique, but it does little for a light roast. The bean is hard, so it produces fewer fines and a relatively even particle size to begin with. The effort rarely repays itself here.

5. The cup keeps changing after you brew it

The floral and fruit aromatics that make a light roast worth drinking are highly volatile, and they are the first thing you lose. Exposing the brewed coffee to a lot of air, or pouring it repeatedly between vessels from a height, removes precisely what you were paying for.

Cooling the coffee quickly after brewing does the opposite and helps those aromatics survive. If you are drinking it iced, brewing directly onto ice in the server suits a light roast well.

6. Store beans at room temperature and grind just before brewing

Light roasts are reported to lose aroma relatively slowly at room temperature. Before reaching for the freezer, an airtight container kept out of direct sunlight and away from heat is enough. A refrigerator is worse, because the beans gather condensation every time you take them out.

Ground coffee loses aroma quickly, so grinding just before you brew makes the clearest difference. If you do not have a grinder, telling us which brewer you use lets us match the grind.

In short

• 92-96C. Do not lower it
• Bloom for 20-30 seconds. A flat bed is fine
• 14-15g per cup, starting at 220-240ml of water
• Medium-fine grind. Sifting fines is low priority
• Do not aerate the brewed coffee. Cooling it quickly helps
• Store airtight at room temperature and grind just before brewing

These are directions that follow from what a light roast is, not the right answer for any particular bean. Origin, variety, processing and roast date all move the ideal temperature and grind. We cup each coffee under conditions adjusted for that bean, and the flavours we write on a product page are the ones we found there.

Try a light roast

HITACHINO COFFEE roasts in Mito, Ibaraki, on a 1980s German-built PROBAT 12kg, keeping the roast light enough for each origin to show its character. Our single origin coffee beans come as whole bean or ground. If you would like to compare a few, the three-coffee tasting set is an easy place to start.