in other preferred embodiments the sheet may have less than four or more than four edges fig2 shows a perspective view of microporous foam sheet 20 including top surface 22 bottom surface 24 and one or more peripheral edges 26 extending between top surface 22 and bottom surface 24 referring to fig3 a process may be used such as that disclosed in commonly assigned u s provisional application 60 380 974 filed may 16 2002 to form marking structures that may be loaded with ink for creating pre inked hand stamps in certain preferred embodiments the microporous foam sheets of fig1 and 2 are exposed to a flash irradiation device whereby energy from a light source exposes certain areas of the foam to the light for melting the surface of the foam so as to form a non porous area at the exterior surface of the foam the unexposed areas of the foam remain porous so that the marking devices can be subsequently used as marking structures in hand stamps for creating imprints on surfaces such as paper envelopes and containers as shown in fig3 a first foam sheet 30 having images flash printed thereon includes a top surface 32 having images printed thereon a bottom untreated surface 34.