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Vanishing foam is a substance applied to an athletic field in order to provide a temporary visual marker for use by both players and referees for the purposes of ensuring fair play. It is used primarily by association football referees to indicate the minimum distance that members of the opposing team must remain from the ball during a free kick, as well as the spot from which the kick is taken. Used mainly at the highest levels of competition, vanishing foam is said to help prevent unnecessary delays by preventing the defensive team from encroaching closer than the mandated 10 yards (9.1 m) from the ball during a free kick, and also by preventing the attacking team from illegally moving the ball from the spot where the referee awarded the kick. Critics, however, argue that its use is the result of referees' lax enforcement of rules already set forth in the Laws of the Game. Its use is not regulated by the Laws of the Game, but by the local governing body of an individual match, league, or tournament.
Vanishing foam is applied from an aerosol can carried by the referee in a holster secured to their shorts. The referee has full discretion on whether or not to use vanishing spray, and opponents are required to retreat 10 yards from the spot of a free kick regardless of whether vanishing spray is used (unless the team awarded the kick elects to take a "quick" free kick with opponents still within 10 yards). It is generally only used when a free kick is awarded where a goal-scoring attempt is highly likely to develop, e.g., it is usually not used when a team is awarded a free kick in its own half of the pitch. When the referee chooses to use vanishing spray, he or she will usually mark the spot of the ball, then pace 10 yards in the direction of the attack, then spray a line marking that distance. Finally, the referee will indicate for the free kick to be taken, usually by blowing the whistle. The marks disappear after about one minute (more like five minutes at the World Cup).
The can contains water (~80%), butane gas (~17%), surfactant (~1%), and other ingredients (~2%). The butane expands when the pressure changes, forming small drops of butane, covered with water, on the ground. Eventually the butane evaporates, leaving only water and surfactant residue on the ground. The US patent application can be viewed here.
In the 1980s the first version was developed by a company consisting, amongst others, of Sir Bobby Charlton and FA referee, Neil Midgely. The English FA rejected the idea, failing even to attend field trials. Approaches to Adidas's English office to develop the product were rejected. The first use in a professional level was in the 2000 Brazilian Championship, Copa João Havelange. A successful commercial version was invented in 2002 by Argentinian entrepreneur Pablo Silva and called it "9-15". The spray has been patented by Brazilian inventor Heine Allemagne since October 29, 2002  although it is not the version FIFA uses. Since then, the spray has been used in many international football competitions. In June 2014 the spray's latest commercial version, "9-15", made its debut in the FIFA 2014 World Cup.
The 2011 Copa América tournament was the first tournament for national teams to use the spray. Its success caused it to be adopted by several national leagues in 2011 in the America's including the North American MLS association.  It has also been used in the 2013 FIFA U-20 World Cup in Turkey, the 2014 UEFA European Under-17 Championship in Malta and Gozo, and the 2014 FIFA World Cup in Brazil.
- Crossman, Steve (2014-06-10). "World Cup 2014: Vanishing foam 'could see more free-kick goals'". BBC.
- Andre Rossi, "", A Brazilian wants to brings the spray to the world", Terra - Portuguese, Mat=y, 9, 2003
- Pablo Silva, "History of the invention", La Nueva News - Spanish, December 3, 2013.
- Heine Allemagne Patent, "", LATIPAT - Spanish
- "Vanishing spray makes World Cup debut". CNN. June 12, 2014. Retrieved June 13, 2014.
- Cesar R. Torres, "Vanishing spray and the future of technology", New York Times soccer blog, August 7, 2011. Accessed July 28, 2012.
- "Brazil 3 Croatia 1". BBC Sport. 12 June 2014. Retrieved 13 June 2014.
- "Vanishing spray used for first time at tournament". BBC Sport. 12 June 2014. Retrieved 13 June 2014.