Abstract: An apparatus and method for making array hybridization chambers with uniform sample volumes. The apparatus employs a spacer to define a hybridization chamber of uniform volume between a slide, substrate, and gasket after the slide, substrate, spacer and gasket have been contacted. The spacer is non deformable or partially deformable and will only allow the adjacent gasket to a similar height or volume. Methods of making the hybridization apparatus and chambers are also disclosed.