Many of my friends were surprised when the referees began pulling out the vanishing spray.
But it's been used in MLS for some time now, so we Yankee fans were not startled at all; we think it's a great tool.
Of course, we Yankee fans like technology in our sports. I guess that's just how we roll.
The vanishing spray contains a mixture of butane, isobutane and propane gas; a foaming agent; water; and other chemicals. When it leaves the can, the gas depressurizes and expands, creating small, water-covered droplets on the field. The butane mixture later evaporates, leaving only water and surfactant residue behind.
You can see the patent, too.
A foaming composition for generating temporary indications, preferably to mark defensive wall lines and spots for free kick shootout in football, where the foam remains stable over a very short but sufficient period of time to take the shot, wherein the composition comprises a propellant, a foaming emulsifier, a cation chelating agent, a preservative and water.