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 .