Abstract: Apparatus is provided for treating articles, such as printed circuit boards and the like, by removing solid particles, such as polymer resists, by a chemical action such as a stripping action, with the chemical action being provided by spraying a solution onto the articles. The removed particles are then separated from the solution, by novel separation apparatus, so that the solution can be re-used. The novel separation apparatus employs one or more screens or filters that are angularly disposed to allow solution to fall through the screen or screens, and solution is provided in such a manner as to wash along or across the screen or screens, to wash particles into a residence zone, from which they may be evacuated. The particles are preferrably propelled from the residence zone on a periodic basis, for subsequent filtration, whereby the solution in which they are carried may likewise be returned for re-use.