A collograph is a print taken from a collage of materials built onto a supporting board, sealed, inked, and impressed on to the paper - usually by running it through an etching press.
The collograph plate may be printed as a relief plate where the raised surfaces are inked and printed or as an intlio plate where the areas below the surface are inked and printed.
The support board for the collograph could be cardboard, metal, wood or plastic. The materials that build the textured surface could be glue, hessian, string, foil, modelling paste, sandpaper... the possibilities are endless. Whatever the material used however, it needs to be able to withstand the pressure of the press and also not damage the press; hence metal objects that sit more than .5mm in relief will damage the blanket on the press. The height or thickness of the material that is adhered to the backplate needs to be considered. If there are several varying heights of raised surface on a collograph plate, the back plate surface will not print as much detail as the higher relief parts of the plate, although the back plate can be incised if detail for both below and above the surface are to be printed.