Abstract: A printing composition comprising magnetic particles suspended in a liquid medium also having therein a coloring agent, the relative amounts of the particles and the coloring agent being controlled whereby the color of the composition is principally that of the coloring agent. The composition can be contacted with selectively magnetized portions of the surface of a drum to provide an image thereon and the drum surface contacted with a sheet which abstracts the printing composition. The composition is useful in an apparatus which includes such a drum, equipment for magnetizing, a set up for contacting the cylindrical surface with the printing composition and a mechanism for contacting the cylindrical surface with the abstracting sheet. Magnetographic color printing results.

Abstract: A printed upon sheet is divided into a plurality of sequentially longitudinally spaced printing fields having a selected field length, said printing fields each being divided into a plurality of longitudinally and laterally spaced printing domains. The plurality of imprints are divided into a plurality of subsets thereof, said subsets having a null set intersection with each other, the union of all of said subsets of said imprints being a set consisting of all said imprints, each of said subsets of said imprints being sub-divided into a different integral number of sub-subsets of said imprints. The imprints are printed on each of the printing fields on the sheet such that each of the sub-subsets of the imprints is printed on only a selected subset of the longitudinally and laterally spaced printing domains, the printing fields having a null set intersection with one another and the selected subsets of the printing domains having a null set intersection with one another.

Abstract: A printing machine (10) is adapted for printing a plurality of imprints (12) onto a sheet (14) divided into a plurality of sequentially longitudinally spaced printing fields (16) having a selected field length and being divided into a plurality of longitudinally and laterally spaced printing domains (18). The machine (10) includes a plurality of spaced printing rolls (20a-20f) having parallel axes (22a-22f) and peripheral cylindrical surfaces (24a-24f) having image transfer regions (26a.sup.1 -26f.spsp.n.sup.f) adapted to print the imprints (12) onto the sheet (14). The rolls (20a-20f) each have circumstances (28a-28f) which are different integral multiples of the field length and which are not integral multiples of one another. Each of the cylindrical surfaces (28a-28f) has a subset of the image transfer regions (26a.sup.1 -26f.spsp.n.sup.