a mask fixture for etching an item includes : a top fixture disposed over the item , including a reservoir centered within the top fixture for containing an etchant ; a bottom fixture underneath the item to be etched including a recessed surface area centered within the bottom fixture ; and an etch - resistant window for holding the item to be etched , the etch - resistant window disposed entirely within the recessed surface area . in addttion , a small via centered within and intersecting both the top and bottom fixtures acts as a path for a high intensity light beam .