small spherical pellets of approximately 1 5 mm diameter or as a powder these desiccant materials are available from delta adsorbents of roselle ill a third requirement is that the material layers 112 and 114 add rigidity to the core 110 to ease handling and to provide the ability to manufacture the composite insulating spacer to precise dimensional tolerances without sufficient rigidity the panes may have imprecise spacing relative to each other which may impact the thermal performance and visual appeal of the insulated glass unit in the embodiment illustrated in fig1 material 114 may be rigid plastic fiberglass composite cardboard teflon or hot melt adhesive in the embodiment shown in fig1 layer 112 is shown as overlying and attached to layer 114 layer 112 may then be a limp or non structural material such as non woven fabric or film layer 112 may be attached to core 110 or layer 114 either by adhesive or wrapped and welded to itself in a seam along the outer face 108 forming a sleeve a final requirement of the material layer 114 is that of ultraviolet uv light resistance in this case the attribute of uv resistance signifies that the material will not crack or disintegrate thereby allowing particles to shed into the viewable window area over the twenty year life of the window the layers 112 and 114 may be permanently applied such as by direct adhesion to the four surfaces 102 104 106 and 108 using a commercially available adhesive such as super 77 spray manufactured by 3m of st paul minn alternately the core 110 may be wrapped by a non woven fabric which is welded to itself in a seam along the outer face 108.