Is it better to screw a thermos flask as tightly as possible?

The sealing property of a thermos is the key to maintaining temperature, and the tightness of closing the lid directly affects the sealing effect. Many users believe that the tighter the lid is tightened, the better, but the truth is not that simple. Excessive tightening may cause a series of problems, while an appropriate degree of tightness is the best choice.

Understand the principle of sealing
The sealing of a thermos cup depends on the moderate compression of the sealing ring between the lid and the rim of the cup. When the engagement reaches a certain extent, the sealing ring will undergo elastic deformation, perfectly filling all the tiny gaps and forming an effective seal. This process requires precise pressure, not extreme pressure. Just like closing a door, what is needed is a perfect fit between the door frame and the door leaf, rather than slamming the door with all your might.

The hidden danger of excessive force
Over-tightening the lid will first accelerate the aging of the sealing ring. Excessive pressure can keep rubber or silicone sealing rings in a highly compressed state for a long time, causing the material to lose its elasticity and instead affecting the sealing effect. Secondly, this may damage the thread structure, especially for some models that use fine-threaded threads. Excessive force may cause the threads to slip, resulting in permanent damage.

Another often overlooked issue is that excessive tightening may make it difficult to open the lid. When the internal temperature changes, the pressure difference will make the already tight lid even more difficult to rotate. This not only brings inconvenience to use, but may also cause trouble when there is an urgent need to drink.

Find the best balance point
The correct degree of engagement should be to feel obvious resistance first and then apply a little force. Usually, when a slight sealing sound is heard or a significant increase in resistance is felt, it indicates that the appropriate sealing state has been achieved. Users can determine this through a simple test: Fill the cup with hot water and turn it upside down. If there is no leakage, it indicates that the sealing degree is sufficient.

Different types of thermos flasks may have different optimal degrees of engagement. Some designs adopt a press-type opening structure, which requires less screwing force. The traditional screw cap type, on the other hand, requires a slightly greater force. It is recommended to read the instructions before the first use to understand the specific requirements of the product.

Daily usage suggestions
After each cleaning, it is necessary to check whether the sealing ring is intact and ensure that it is correctly in place. When closing the lid, be sure to keep it vertically aligned to avoid tilting and excessive pressure on one side. Regular replacement of the sealing ring is the key to maintaining a good seal. It is generally recommended to replace it every six months to one year.

If it is found that leakage still occurs even when a very strong air force is applied for compression, it is very likely not a problem with the screwing force, but rather that the sealing ring needs to be cleaned or replaced. At this point, efforts should not be further intensified. Instead, it is necessary to check whether the sealing system is in good condition.

Handling of special circumstances
When filling carbonated beverages or liquids that tend to produce gas, it is not advisable to tighten the lid too much. Because the gas produced will increase the internal pressure, a too tight lid may have difficulty releasing the pressure. When taking a flight, due to changes in air pressure, you can loosen the lid appropriately to avoid difficulty in opening it upon landing.

Remember, the design of the thermos has taken into account the needs of daily use. Through meticulous design, engineers ensure that the sealing system achieves the best effect with an appropriate screwing force. We don't need to use brute force to go beyond the original intention of the design, but should learn to coexist harmoniously with the product.

Correct usage habits can not only extend the service life of the thermos cup, but also make daily use more relaxed and pleasant. Moderate screwing is not only a sign of care for the product but also a responsibility for your own user experience.