Most of the masks fog when they are new. This is caused by a very thin layer of silicone film, placed on the glass to protect it from scratching during the manufacturing process.
The protective coating is oily. The oily surface favors condensation of water vapor and this is what makes your mask fogging.
How to fix it? Simply by removing the post-production film. There are many options to do so. Burning, toothpaste, dishwasher, dedicated drops, applying detergents – all of these methods eventually lead to removing the oily residue. Additionally, applying anty-fog spray or saliva will decrease the surface tension of the moisture on the glass of your mask and prevent fogging even further.
Wait a second! What does it mean that my mask starts fogging again after a while?
Remember what we said about oily surface? Greasy fingers can easily make the surface of your mask oily again! Keep it in mind when touching your mask after a lunch break or after using creams! In any case the solution is exactly the same as with the brand new mask – get read of the oily residual and apply syntetic or natural anti-foggers (spray or spit 🙂 .