Cold brew coffee is suited to being prepared in advance, left in the fridge to steep slowly, and then drunk straight away in the morning, on the commute or at the weekend. It does not matter if you do not have a dedicated cold brew pot at home; a glass jar with a lid, a measuring cup, filter paper and a fine sieve are enough. What really affects the result is container capacity, the amount of ground coffee, grind coarseness, steeping time and the filtration method.

First look at how much water the container you have on hand can hold. Taking a common 500 ml glass jar as an example, to make a cold brew you can drink straight, use 35 g of coffee beans and 500 g of water, a coffee-to-water ratio of about 1:14. If you prefer it stronger, to add ice or milk afterwards, you can use 40 g of grounds with 500 g of water. For a larger container, just scale up according to the same ratio; weighing is more consistent than pouring water by the markings.

Grind the coffee beans to a medium-coarse particle, with an appearance close to coarse granulated sugar. If the grind is too fine, the powder easily passes through the filter paper, there will be obvious sediment in the cup, and after a long steep it may also taste dry and astringent; if ground too coarse, the aroma and sweetness are released more slowly. A home electric grinder can be run in two short bursts to reduce the concentration of fines and make the steeped liquid clearer.

To make it, pour the ground coffee into a clean glass jar, add room-temperature drinking water, and stir gently with a spoon so that all the grounds come into contact with the water. Close the container tightly and put it in the fridge to chill for about 12 hours. When the time is up, line a strainer or filter cup with filter paper, pour the liquid out slowly, and let it drip naturally; there is no need to press hard on the coffee grounds.

The fridge temperature is usually between 4 and 8°C, and the cold brew steeping time can be set at 10 to 14 hours. If using a light roast, around 12 hours easily balances fruity aroma and a refreshing feel; a medium roast can be extended to 13 or 14 hours to make the sweetness and mouthfeel fuller. Steeping beyond 16 hours does not necessarily make the flavour stronger; instead it may add woody and harsh bitter notes.

The shape of the equipment also changes the extraction performance. In a wide-mouth jar the coffee bed is shallower, and the grounds and water mix easily, making it suitable for direct steeping; in a tall, narrow cold brew bottle the coffee bed is thicker, so after adding water you should gently swirl the container to fully wet the grounds at the bottom. If using a cold brew pot with a filter mesh, do not pack the mesh too full; leave room for the grounds to absorb water and expand, and the filtration will be smoother.

If you like bright fruity aromas, you can choose Qianjie Ethiopia Huakui. After low-temperature steeping, its tropical-fruit-like aroma becomes softer, with strawberry and passion fruit notes hidden in the clean sweetness. Steep at a 1:14 ratio for 12 hours, and drinking it straight over ice is lighter; if you want to make a sparkling cold brew, mix the finished brew with unsweetened sparkling water, and the fruity aroma will seem livelier.

Qianjie Colombia Sidra suits home drinkers who want a more obvious juicy feel. Once the cold brew is finished, flavours such as blueberry, grape and apricot become rounded, and the acidity is not sharp; it is suitable to use a 500 ml jar with 40 g of grounds and steep for 12 to 13 hours. After adding ice, the finished drink still has enough strength, and a small amount of soda water can also be added to make a refreshing summer drink.

If you only have filter tea bags or non-woven filter bags at home, you can also make a simple cold brew. Put the ground coffee into the filter bag and place it in a water bottle with a lid; be careful to tie the bag tightly to prevent the grounds from spilling out; keep the water at about 80% of the bottle's capacity to leave room for shaking. At the end of steeping, simply lift out the filter bag, then filter once more with filter paper; the mouthfeel will be cleaner than just lifting out the bag.

After filtering, the cold brew liquid can be put into a sealed bottle and refrigerated; it is recommended to drink it within a few days, and to shake it gently before serving. If it tastes too weak, you can add more ground coffee or extend the steeping by two hours; if the aroma is not enough, you can adjust the grind one step finer; if it is clearly bitter, shorten the time or stir less. Fix a set of parameters according to your equipment capacity, and cold brew can go from an off-the-cuff steep to a stable, refreshing home coffee.