All polymers (acylic (Klasse) or other polymers (Wolfgang)) typically require a period of between 12 -24 hours to cross-link, meaning that the product forms a covalent (molecular) bond with the surface it’s applied too, it becomes stable and inert so that its chemistry will not be effected by water or the application of other products
For more information see “Polymers” one of a collection of detailing articles on DetailingWiki; (Wikipedia® is a registered trademark of the Wikimedia Foundation) a series of informative, knowledge based, unbiased articles dedicated to automotive detailing