Anti Fog

What are the best chemistry ANTI FOG goggles? or methods to defog goggles?

i have a pair of chemistry goggles similar to these with the exception that the vents are on the top and bottom more like slits. whenever i have chemistry lab they fog up continuously within 4 minutes of taking them off and cleaning them. what do you guys recommend as the best goggles or methods to keep goggles de-foged?

Spit on the inside of the lenses.
I know it is crude, but spitting on them and wiping them is the only thing I know of that works.

Clarity Defog It Anti-fog Liquid Demo.mpg

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