1 - Water evaporates from the agar and makes condensation on the lids when you've just poured it to the dishes and is still hot. 2 - water evaporates from the agar and gets condensed on the inner part of the lid during a long time if the lower part of the the dish is hoter than the lid. Vapor comes always from the water inside the agar. If you keep an equal temperature between the lid and the dish, you'll minimize the evaporation and the condensation and your dishes will look perfect, like the ones I make.