They're using a coating on the inside of the glass. DAKD Jung has posted about this. I'd be curious to know how similar Hulten and DAKD Jung's formulations are.

They're using a coating on the inside of the glass. DAKD Jung has posted about this. I'd be curious to know how similar Hulten and DAKD Jung's formulations are. It was made to sound rather involved when I read DAKD Jung's description of it.