Video: Tyndall illuminated spraying the back of a mini illustrating invisible mist
This video clip shows the back end of vehicle being sprayed by an operator wearing an air-fed visor sat on his haunches. The spraying takes place in a conventional spraybooth with the ventilation running. There is a black backcloth fixed to the walls of the booth behind and to the side of the sprayer. A high-intensity parallel-beam light has been set up behind the sprayer to illuminate the area around his visor. This has the same effect as being in a darkened building with a shaft of sunlight shining through, which makes all the dust in the beam visible.
Without the high-intensity light and black backdrop, the camera would only see what the operator normally sees ie a small amount of spray from the gun that seems to be instantaneously carried away through the floor by the ventilation. With the special lighting, the operator can be seen engulfed by paint mist, which spreads through the booth like smoke. After about 30 seconds the sprayer is asked to stop spraying and remains crouching in the same position. The camera clearly shows the area around the sprayer's visor continues to have large quantities of paint mist circulating for tens of seconds afterwards. This is significant because most sprayers would have lifted their visor straight after spraying finished to see the painted surface with the naked eye. They would then be breathing in the paint mist unaware it remained there for some considerable time (which is known as the 'clearance time' and may be as much as five minutes in a spraybooth or up to half an hour in a spray room).