Airwaves, apparently. The strong minty chewing gum that you masticate and at the last moment, breathe out into your cupped hands so that your breath stings your eyes and tears begin to flow. That was the advice from Joe Keirs on Thursday, which he had picked up on some acting grapevine for when my character needed to cry. I had to express several other extreme emotions but it was only weeping that worried Joe; he needed to see real tears.
He needn't have worried. One of my few talents is to produce tears more or less at will. It doesn't happen instantaneously but it does happen in real time. The pressure builds up behind my eyes and water emerges and drips down my cheeks in either laughter or sadness.
Assuming it is sadness I'm expressing, am I actually sad at that moment? Yes and no. Part of me is mourning a loss - a relationship ending, someone dying - but another part of has gone into neutral and is observing my reaction. This acting is the opposite of the spontaneous emotion. Then an idea or awareness in my mind overwhelms my body and I begin to cry, but in front of the camera it is my body generating the emotion and sending it to my mind, part of which accepts it and part of which recognises that the situation is unreal and it so it does not need to be involved.
Which means that when the director calls "cut", I can immediately snap out of the emotion and scene and return to whatever I was doing or thinking about before filming began. And if he needs to refilm I can turn the waterworks on again. It is, after all, just The Crying Game.