by the mask so as to be wettable with an aqueous liquid at least one of the other wettable second portions being totally isolated from the other wettable second portions by some of the mask so that aqueous liquid will not flow from the one wettable portion to the another wettable portion until an overflow amount of aqueous liquid is added to the one wettable portion in an amount sufficient to bridge across the mask and an absorbent material mounted at one side of the surface in position to receive liquid from the slide the method of use features confining aqueous reagents to the area restricted by the hydrophobic mask except for when additional amounts are added to force at least some of the liquid to move towards a side edge of the slide where most of the liquid is absorbed application_number US 79241497 A description the discussion hereinafter is of the preferred embodiments wherein immunostaining of cells is done on a support comprising glass slides bearing a preferred hydrophobic mask of a particular configuration and a preferred absorbent material in addition the invention is useful regardless of the type or configuration of the mask that is used and regardless of the type of absorbent that is used provided a portion of.