As many of ya'll who have processed BHO know, water can find its way into the solution from the ice that forms at the edge of the evaporating pool. I have found two ways that work well to prevent that happening.
The first is that if the humidity isn't too high, simply setting the evaporation dish in hot water throughout the extraction process, not just to purge, will suffice.
When the humidity gets too high, we use a deep stainless bain marie vessel, so that the edge of the evaporating pool has a deep layer of butane floating over it, so that the moisture laden air is unable to reach the dew point area. That bain marie vessel sits in another bain marie container, full of hot water.
The first is that if the humidity isn't too high, simply setting the evaporation dish in hot water throughout the extraction process, not just to purge, will suffice.
When the humidity gets too high, we use a deep stainless bain marie vessel, so that the edge of the evaporating pool has a deep layer of butane floating over it, so that the moisture laden air is unable to reach the dew point area. That bain marie vessel sits in another bain marie container, full of hot water.