1. Percolation vs Immersion Brewing

How coffee interacts with water can completely change how extraction happens. Most brewing devices will fall into two categories: immersion or percolation.

In immersion brewing, the coffee grounds are fully submerged in water for a period of time. The water and coffee stay together, allowing extraction to happen throughout the brew.

Think of it like steeping tea.

Examples:

• French press

• Clever Dripper

• AeroPress

Because all of the water is in contact with the coffee at once, immersion brewing tends to be forgiving, consistent and easy to control, making it a great place to start for beginners.

In percolation brewing, water passes through a bed of coffee grounds and eventually through a filter.

Think of it like water travelling through soil. Where the water flows and how quickly it moves will affect what gets carried with it.

Examples:

• V60

• Kalita Wave

• Chemex

• Batch brew

Here, extraction is influenced by how water flows through the coffee bed. Your pouring technique, flow rate, filter, and how evenly the coffee bed is prepared can all impact the result.

Because percolation brewing sees fresh water continuously pass through the coffee bed, rather than the coffee remaining immersed in the same body of water, the two methods can reach similar extraction levels while tasting very different in the cup. A French press can sit for several minutes without necessarily becoming unpleasantly bitter, while a V60 can produce a highly extracted cup in a much shorter brew time.

2. Even Extraction

Now that you have your weapon of choice, the next question is: how evenly are we extracting the coffee?

Freshly roasted coffee contains trapped carbon dioxide (CO₂), which is gradually released over time. When coffee is very fresh, this gas can make it harder for water to evenly saturate and pass through the grounds, making consistent extraction more difficult.

This is where resting your coffee comes in. As coffee rests after roasting, some of that CO₂ naturally escapes. How long it needs to rest will vary depending on the coffee and roast style, but as a general starting point, giving your coffee around two weeks to rest post-roast can make it easier to brew consistently.

Once we start brewing, the goal is to saturate and extract the coffee as evenly as possible. Water naturally follows the path of least resistance, so if some areas of the coffee bed are easier to pass through than others, more water will travel through those areas. This can leave some of the coffee over-extracted and other parts under-extracted within the same brew.

Ensuring good coffee-bed preparation, consistent pouring, and appropriate agitation can all help encourage water to move through the coffee more evenly.

3. Grind Size

Grind size plays a major role in both extraction and water flow, making it an important part of dialling in filter coffee. Finer coffee has more surface area available for water to interact with, making it easier for water to dissolve the compounds within the coffee. In percolation brewing, a finer grind also creates more resistance to water passing through the coffee bed, generally resulting in a slower drawdown and more contact time.

A coarser grind does the opposite: water can pass through the bed of coffee with less resistance, generally resulting in a faster brew and lower extraction.

You can often taste this difference in the cup. If your coffee tastes sour, sharp or thin, grinding finer may help increase extraction and bring out more sweetness and balance. If it tastes overly bitter, dry or harsh, grinding coarser may help.

4. The Coffee

Not all coffee behaves the same way in your brewer.

Different varieties, origins, processing methods, and roast styles can behave differently, even when brewed using the exact same brew recipe.Coffees from different origins have their own inherent characteristics, influenced by factors like variety, growing conditions and altitude, while different processing methods can further change the coffee’s structure and flavour profile. Each coffee contains different compounds in different concentrations, and those compounds don’t all dissolve at the same rate. Lighter and darker roasted coffees also extract differently.

As coffee is roasted darker, its internal structure becomes more porous, making it easier for water to get in and dissolve the compounds inside. As a general rule, darker roasts can be easier to extract, while lighter roasts can take a little more work to get the flavours we want into the cup. This is why you can't always take a recipe that works beautifully for one coffee and expect it to work the same way for another.

5. Water

Despite making up the vast majority of your cup (roughly 98.5–98.85%, to be exact!), water is often overlooked as one of the most important variables by brewers.

The minerals in your brewing water can affect how coffee compounds dissolve and, importantly, how we perceive acidity, sweetness, bitterness, and body.

Water quality and mineral content can vary significantly across Australian water supplies, meaning the same coffee brewed with the same recipe can taste noticeably different from one location to another.

For brewing at home, filtered water is a great place to start. It might sound like coffee-nerd overkill, but there’s a reason your favourite café will almost certainly have a water filtration system connected to its espresso machine. Filtering reduces unwanted tastes and odours, while retaining the minerals that help coffee extract and taste its best.

Water temperature also plays an important role in brewing great filter coffee. Hotter water generally extracts coffee more efficiently, while cooler water extracts more gently.

The temperature of your water can therefore be used to fine-tune how a coffee tastes. Cooler water can sometimes produce a lighter, brighter cup where acidity is more prominent, while hotter water can increase extraction and bring out more sweetness and body — although pushed too far, it can also emphasise bitterness. As with most things in coffee, taste is the best guide. For best results, we like to brew filter coffee between 88°C and 96°C. A temperature-controlled kettle is your best friend here.