The control of "water flow" is the key to making coffee by hand! If the water flow is large or small, it will lead to insufficient or excessive intake of coffee powder, which will make the coffee full of sour and astringent taste, and also easy to produce miscellaneous taste. In order to make the water flow into the filter cup stably, the quality of the hand washing pot has a very important impact.

The experiment shows that the common coffee pot mouth uses water drip to feed water, which forms a water drop shape, and its weight is relatively concentrated at the bottom. When it contacts the powder layer, it has a certain impact force, which can not spread evenly, but increases the probability of uneven draught of the coffee powder layer. The duckbill can form water droplets when it comes out of the water. Compared with the water droplets, the water droplets are a uniform ball, which can spread out evenly when contacting the powder layer.