The present invention related to a method for treating a surface with a gel, as well as to a treatment gel.The treatment may be a decontamination, etching or surface degreasing treatment, for example.The method comprises in this order, the following steps: applying the treatment gel on the surface to be treated, maintaining the treatment gel on the surface to be treated at a temperature and relative humidity such that the gel dries by breaking up and that it has the time to treat the surface before forming a dry and solid residue, and removing the dry and solid residue from the treated surface by suction or brushing.The gel comprises a viscosing agent, a treatment agent and optional an oxidizing agent.