Coffee quality depends on a combination of factors. Fresh beans, measured by both how long it’s been since the beans were roasted and the time elapsed since grinding the beans, are imperative. High quality beans (measured by the specific crop, processing, handling, etc.) are, obviously, desirable, but the highest quality beans are all but useless if stale. Clean good-tasting water must be used, and the coffee must be brewed with clean equipment at the proper temperature for the proper amount of time

Simply buying top-quality beans is no guarantee of great coffee; if those beans are stale, the water quality poor, the brewing temperature low, or your equipment dirty, you will have wasted money on those expensive beans. Lesser quality yet freshly roasted beans, ground before use, will almost certainly be superior to a higher quality sample that is stale.

With all brewing methods, the goal is to balance strength and yield. These two elements are distinct but often confused. As noted in the section on water quality, brewed coffee is over 98 percent water; this is a measure of its strength–i.e., how much extracted coffee there is as a ratio to water. Not counting espresso or Turkish coffee, this mainly refers to the concentration of solubles; with espresso, that can be broadened to include emulsified oils (Turkish coffee often has a significant component of suspended solids). If your ratios fall outside of the proper range, the coffee is perceived as too weak or too strong. Most commonly this is a function of the quantity of ground coffee used for any given volume of water. However, the quality of solubles that are extracted determine another factor, the yield. If too little is extracted from the ground coffee (because the grounds are too coarse or the water contact time is too short), then the coffee will miss essential taste components. If too much is extracted (the coffee was ground too finely or the contact time is too long), then the brew will be bitter. Rather than being a measure of the total quantity of solubles extracted, yield is a measure of the desirable range of extracted solubles. To put it grossly, if you mix hot water and coarsely ground coffee in a one to one ratio and allow it to extract for thirty seconds, you will have a cup with a very strong grassy taste. A lot was extracted just because of the sheer quantity of coffee, but not enough of the desirable components. Similarly, if you add a tablespoon of finely ground coffee to a quart of hot water and let it steep for ten minutes, you will have a weak yet bitter brew.

For coffee brewing, the Specialty Coffee Association of America (SCAA) prescribes a water temperature of 89- 97 degrees C (195 – 205 degrees F); see The Basics of Brewing Coffee by SCAA Executive Director Ted Lingle. Avoid boiling then cooling the water to the proper range, or at least letting it boil for more than a few moments; boiling hot water rapidly loses dissolved air and will taste flat. If the water is too cool, the brew will be sour and under extracted. The temperature range during brewing should not vary by more then a few degrees, or extraction will not be optimal. Temperature loss often occurs as a result of heat absorption by the equipment itself (for example, if an espresso machine’s porta filter is not kept warm between shots by storage in the machine) or into the atmosphere (as in a uninsulated glass French press during the approximately four minute steeping period). Pre-warming the equipment or insulating it, respectively, will solve these problems.

Coffee is 98.5 to 99 percent water, so water quality will critically affect the resultant brew’s taste. When making coffee, you should only use water that tastes good enough to drink straight. As a result, the best cups of coffee are made with filtered tap water or bottled water. Carafes or sink-based filters will likely perform better and have a lower per-gallon cost than the modest charcoal filters that some manufacturers include with their auto-drip machines. Do not mistake distilled water for filtered: the former is missing minerals that contribute to the water’s taste and aid in extraction. When certifying a coffee brewer, the SCAA uses fresh cold water containing a formulation of between 50 to 100 parts per million dissolved minerals. The water should be fresh; it it has been sitting too long (or has been heated then cooled), it will be missing the dissolved air that is an important component of the water’s taste.The water should also start cold: hot water has lost some of its dissolved air, and may have picked up minerals or solubles from your pipes.

A standard “cup” of coffee uses six ounces (177 ml) of water. The SCAA’s standard measure of ground coffee for this quantity of water is 10 grams (+/- 1 gram) or slightly over a third of an ounce (or, simply, two tablespoons). Since the ground coffee will absorb water, you will be left with approximately five and one-third ounces of coffee. Unless stated otherwise, the preceding is the ratio used in the FAQ’s descriptions. Most coffee scoops and water chambers will be calibrated to this standard, but that is not necessarily so; the country of manufacture may result in different calibrations, and some measures may simply be wrong. Accurate scales can help verify how much a particular scoop holds.

In parts of the world where a coffee cup is defined as a different quantity, the coffee/water ratio remains the same (e.g., in Europe, 7 grams per 4.25 ounces).

For larger quantities, use 3.75 ounces (+/- 0.5 ounce) of ground coffee per half-gallon water, or 2.25 gallons water per pound of coffee (for commercial, urn-style brewing devices), slightly less than the ratio for a single cup. For metric measures, use 55 grams (+/- 5 grams) per liter.

For those who find that the two tablespoon/6 ounce ratio produced too strong a cup, simply reduce the quantity of coffee used until the desired strength is reached.

Recommendations to grind more finely and thereby use less coffee are simply wrong. Grind fineness is related to steeping time; using less but finer coffee will make the resultant product bitter; using less coffee under these circumstances will make a weak, bitter cup.

Optimally, brew a fresh batch whenever you want coffee. To keep coffee hot for shorter periods of time, or for travel, use a thermally insulated container; an enclosed container will reduce the loss of the aromatics that constitute an essential part of the overall flavor (but see here). Insulated containers with glass internals, though somewhat delicate, have the least effect upon the coffee taste, followed by good quality stainless steel. Coffee with significant residual sediment, such as coffee brewed in a French press, fares less well when kept hot for extended periods; the sediment continues to extract, making the coffee bitter.

Direct heat—e.g., via a warming plate—should not be applied to brewed coffee, at least not for more than few minutes; continued heating will make the coffee bitter. This issue is primarily a concern for autodrip coffee makers; choose a model that dispenses into an insulated carafe over one that uses a warming plate.

Reheating coffee in the microwave is controversial; the key issue may be the uneven heating microwaves are known for. There are those who theorize that parts of the coffee that overheat may taste unpleasant, thereby spoiling the cup as a whole.

The issue of the “right” coffee cup seems to have mainly anecdotal responses. In theory, the best containers are simply those that keep the coffee hot and do not add flavors of their own. Heavy, pre-warmed ceramic cups probably serve those criteria best.

Insulated plastic and metal containers are commonly used for travel mugs, as they can be durable and relatively lightweight. Theoretically, they are inert (assuming stainless steel or a quality plastic), but some aficionados swear that they can detect off-flavors, thought this may merely be evidence of lower-quality material.

Disposable cups are almost invariably made from paper or expanded polystyrene (“foam”), the latter often incorrectly referred to as Styrofoam (a trademark of Dow Chemical and a different product). There are instances where coffee tastings and sensory skill sessions have been ruined by a perceived “papery” aspect from paper cups, and other people avow that foam cups contribute similar off-tastes. Paper cups usually have a wax or plastic coating to prevent the liquid from soaking through the paper, and this substance may create a brand-by-brand difference in cup quality.

Drinking from a lidded container is detrimental to the coffee’s flavor, as the lid will prevent aromatics, vital to the overall perception of taste, from reaching your nose. On the opposite end, the very wide “bowl style” cups lose their heat very quickly—the high surface area to volume ratio causes rapid evaporation. Optimally, choose a shape that both retains heat and channels the aromas to your nose.

Good quality coffee will commonly have some bitter elements, but they should exist in balance with other aspects; bitterness should not be an overwhelming component. Unfortunately, most people are rarely served anything but poorly prepared coffee that may also have been sitting on a warming element for extended periods, so the standard experience is that coffee is bitter.

First, be certain that the problem is that your coffee is too strong or too weak. Often people will confuse “bitter” with being “strong.” If your coffee is unpleasantly bitter, one cause may be that your grind is too fine for the steeping duration; use a coarser grind. A lower-quality grinder will also produce a lot of dust, which will make the coffee taste bitter. If the coffee is too coarse for the brewing technique, your coffee will be under extracted; use a finer grind. Your coffee isn’t weak in the sense that the taste is diluted, it’s because many of the desirable flavor elements (which don’t all extract at the same time) are still in the grounds and simply never made it to your brew. See also section 1.1, Overall factors.

There also is a myth that conflates weakness and bitterness in that some people believe that using too little coffee (a weak cup) will also almost invariably cause bitterness. The theory appears to be that since using an insufficient amount of ground coffee will result in there not being enough desirable coffee components available, the bitter elements will rush in to make up the difference. This is an erroneous belief; the various components of the bean are extracted over the course of the steeping period (the length of which varies as a function of grind coarseness) in a definite progression, with the desirable components mainly extracted during the first third of the extraction period, the extraction sharply dropping off during the second third, and the bitter and astringent components becoming predominant during the final third.

Another issue is degree of roast. Some roasters over-roast their coffee as a matter of course, and the distinctive taste of charcoal may therefore cause the coffee to be labeled as strong. It isn’t: the roasted beans are defective. Buy a different coffee, perhaps from another roaster. Or, the roaster may also have “baked” the coffee, which means that certain physical and chemical changes didn’t occur during roasting, and the coffee will taste flat no matter what you do.

Ultimately, if your beans are good, and the grind is appropriately fine for your brewing technique, then simply adjust the amount of coffee you use. If your grind is right, then you’ll be extracting a desirable profile of solubles from the grounds, just in different quantities.