From my experience pouring commemoratives, if I pour out of the clean side of the ladle, then the hardened dribble falls into the mold at the end of the pour, landing in the area formed by the plunger and base. This often resulted in badly formed bases with open bubbles and creases. So, when I started filling the mold from the dribble side of the ladle, it was the nice clean hot glass that was available for the base forming. Then I noticed how I had "V" shaped straw line on the domes, just like so many old insulators have. It makes perfect sense. I pour out of the dribble side of the ladle, and I have way fewer rejects. Just like workers at Hemingray, Brookfield, etc. must have discovered over 100 years ago.