Generally illegal posters have to be removed quickly, if they are neglected for couple of weeks the posters will becomes thicker day by day. Illegal posters also attract graffiti and promote bad events.
Posters make property to look poorly maintained and abandoned. Soits important to remove posters ASAP once they are posted.
We remove all excess posters by hand and then use hot water with a specialized chemical to remove the debris and clean the surface free from glue.