Pilkington, the UK specialist glassmaker, unveiled its version, Pilkington Activ, to much fanfare last February.
However, Pilkington's full commercial launch will not be until March in Europe and October for the UK.
One analyst said that, at best, the presence of Aquaclean will make Pilkington's launch more difficult: "It could also set a cap for what Pilkington can charge."
Pilkington Activ will be more expensive than Aquaclean because it is more sophisticated. Both products are hydrophilic, meaning that they shed water. But Pilkington Activ has added photocatalytic properties, which break down deposits into carbon dioxide and water by reacting to sunlight.
Both will be branded "self-cleaning glass" - a market that analysts estimate could be worth 200m in Europe by 2005. Pilkington expects sales of Eu30m-Eu40m (20m-25m) next year.
Saint Gobain has already begun attempts to diminish its rival's product. In a technical document the company claims: "The self-cleaning coating of a photocatalytic glass results in loss of light and a visible colour tint, which may be a nuisance to the user."
Nevertheless, a spokesman claims the company has its own photocatalytic product in development and "would be in a position to launch" before October if necessary.
Much of the tussle between the two makers may come down to price but Kevin Cammack, building products analyst at Merrill Lynch, sets some store by the quality of Pilkington Activ.
He said: "Getting to market early may give Saint Gobain a head start but whether four months will make all the difference against a superior product is questionable."
American rival PPG has launched a photocatalytic glass in the US called SunClean.