The anti fog function of ski goggles is mainly on the inner lens. The material of the inner lens is cellulose acetate sheet (CP sheet), which is a type of resin. This type of sheet has strong water absorption ability. After being treated with anti fog liquid, the sheet can remain non foggy for 20 seconds on the outlet hole of a 6CM diameter sink at a water temperature of 75 degrees Celsius.
The price of cellulose acetate boards is very expensive, and domestic boards cannot meet optical standards. More than 95% of anti fog sheets are imported, and anti fog is permanent.
So when buying ski goggles, you need to buy cellulose acetate board as the snow mirror for the endoscope