Acidity and bitterness are not mistakes
Acidity is a natural part of coffee. It can recall citrus, apple or ripe fruit and give a cup brightness and structure. Bitterness also has its place: it appears in cacao, toasted nuts and coffee itself. The problem begins when either attribute dominates, becomes harsh or leaves the drink feeling unfinished.
Before correcting anything, describe it more closely. Is the acidity juicy or sharply sour? Does the bitterness resemble dark chocolate, or does it leave persistent dryness? The more precise the observation, the more useful the next change will be.
When coffee tastes sour or hollow
A sour, salty, vegetal or very short cup may indicate that too little has been extracted. In filter coffee, a grind that is too coarse, short contact or uneven wetting can leave part of the bed underused. In espresso, distribution and channels that give water an easy route through the puck also matter.
Begin by grinding slightly finer. You can also extend contact a little or make the pour more even. If your water is unusually cool, increasing temperature may make extraction easier. Change one thing, taste again and only then decide whether the recipe needs another move.
When bitterness, dryness or roughness appears
A dry, rough cup with lingering bitterness may be over-extracted, but not always. Roast level, the coffee itself and uneven extraction can also create bitterness. If the same cup tastes sour and bitter, uniformity is an important clue: some areas may have received much more water than others.
For filter coffee, try a slightly coarser grind or reduce agitation. With espresso, check distribution, tamp and flow before dramatically shortening the drink. Grinding finer does not improve extraction forever; beyond a certain point it can encourage channelling and make the result less even.
A small method for correcting any coffee
Keep dose and water fixed, brew the coffee and write down two or three words about its flavour. Then choose one adjustment—usually the grind. Repeat and compare once the cup has cooled slightly, as many nuances become easier to recognise away from the highest temperatures.
The aim is not to remove all acidity or bitterness. It is to find a relationship with sweetness, clarity and a pleasant finish. The recipe is simply a tool for getting there. Learning to correct coffee begins less with the timer than with paying attention to what we are drinking.