That's a real possibility Mike. You need to develop a steady rhythm to cast good balls. There's no time for inspection of individual balls. Your first few may be wrinkled or have voids until the mold heats up. As Devil stated, when the temperature is right the sprue should take a few seconds to set. Once it sets, dump the ball on something soft (I use a folded towel) and fill the mold immediately. If the sprue seems to be taking longer and longer to set slow down a little between balls. Pretty soon you will get a feel for the speed that works best.