I think that the yeast in combination with not using a bag for the grape skins does it. When I open up the fermenter, the skins and oak lay on top of the wine in a nice cap. Then, as I stir them back in to the wine, I get some really good foam for a bit. It calms down after a minute or so and I snap the lid back down and replace the bubbler. Perfect.
Yep, same experience here. Gotta wait for the foam to settle to get a good SG reading.