1. Poor sealing: check whether there is a gap in the bottle cap or other places. If the cup cap is not tightly closed, the water in your thermos cup will not be warm soon. The water container made of stainless steel and vacuum layer has a cover on the top and is tightly sealed. The vacuum insulation layer can delay the heat dissipation of water and other liquids inside, so as to achieve the purpose of heat preservation. The falling off of the sealing cushion and the lack of tightness of the cup cover will make the sealing poor, thus affecting the thermal insulation performance.
2. Air leakage of the cup: there may also be a problem with the material of the cup itself. There are defects in the process of some thermos cups. Pinhole sized holes may appear in the inner tank, so as to accelerate the heat transfer between the two layers of cup walls. Therefore, the heat will be lost quickly.