In both types of dutch weave the sum derived from multiplying the number of weft wires in a given measurement by their diameter, results, in theory, in a specification with no open space. Because the wires are driven together during the weaving process, the aperture size cannot be calculated in the normal manner. There are two methods by which the aperture size can be determined: bubble point testing and glass bead testing. See-"bubble point test" See-"glass bead test"